# Suppression of KIF22 Inhibits Cell Proliferation and Xenograft Tumor Growth in Tongue Squamous Cell Carcinoma

Authors: Yi Liu; Rong-Hua Li; Gang Ren; Jin Jiang
Journal: BioMed Research International
 (2020)

---

## Abstract

Background. Oral carcinoma is the sixth most common cancer and is a serious public health problem, and tongue squamous cell carcinoma (TSCC) is the most common type of oral carcinoma. Kinesin family member 22 (KIF22), also called as kinesin-like DNA binding protein (KID), is a microtubule-based motor protein and binds to both microtubules and chromosomes, transporting organelles, protein, and mRNA. This research aimed at investigating the prognostic significance of KIF22 in TSCC. Patients and Methods. This retrospective research collected 82 paired tissues with TSCC. KIF22 protein expression level was detected by immunohistochemical staining. Suppression of KIF22 with shRNA in CAL-27 and SCC-15 cells was to observe cell proliferation in vitro and xenograft tumor growth in vivo. Results. In TSCC tissues, the protein expression level of KIF22 was increased and correlated with tumor stage, clinical stage, and lymphatic metastasis (P=0.013, P=0.034 and P=0.015, respectively). Suppression of KIF22 inhibited cell proliferation and xenograft tumor growth. Conclusion. KIF22 might play an important role in the progression of TSCC and could serve as a therapeutic target for TSCC.


---

## Body

## 1. Introduction

Oral carcinoma is the sixth most common cancer and is a serious public health problem [1, 2]. Recent reports estimated 49,670 patients suffered from oral carcinoma in the United States of America and 9,700 deaths in 2017 [3]. In 2018, this increased up to 51,540 and caused 10,030 deaths in the United States of America [4]. Shield et al. reported that the proportion of oral cancer rose to 28.6% in all cancers in North Africa and Europe [5], and this may be due to the unexpected rise of tongue squamous cell carcinoma (TSCC) [2]. It is well known that TSCC is the most common type of oral carcinoma, which has a high potential for locoregional invasion and nodal metastasis, so patients had a poor prognosis [6]. Therefore, early detection of TSCC is more important. Although new drugs and therapies improved quality of life and survival time, they were limited by side effects. Despite increasing studies on the molecular mechanism of TSCC, the 5-year overall survival of TSCC patients is still only about 50% [7]. One reason is that tumors are often diagnosed at a later stage and therefore have spread to the cervical lymph nodes. Another reason is the development of locoregional recurrences [8]. Some biomarkers which service for diagnostic and prognostic have been studied in recent search for TSCC, but no results have proved suitable for routine use in clinics.Vale et al. firstly reported kinesin in giant squid axons [9]. Subsequently, it has been reported in different species and tissues, such as mammalian neuronal cells, sea urchin eggs, and Drosophila [10–12]. Kinesin family member 22 (KIF22), also called as kinesin-like DNA binding protein (KID), is a microtubule-based motor protein and binds to both microtubules and chromosomes, transporting organelles, protein, and mRNA. Kinesin family has been reported to be associated with important transporting molecules in cells [13, 14]. In recent years, kinesin family was reported to play important roles in cancers. KIF26B was overexpressed in breast cancer and associated with poor prognosis, larger tumor size, and lymph node metastasis, and the expression of KIF26B was positively correlated with estrogen receptor [15]. KIF22, as a binding protein of microtubules and chromosomes, has several reports [16]. In recent studies, transcription regulator was reported in some cancers. Yu et al. observed that inhibition of KIF22 decreased cell proliferation in cancer by delaying mitotic exit [17], and they also found that KIF22 protein and mRNA had a high expression level in several cancer tissues and promoted cell proliferation by downregulating CDC25C to accelerating mitotic exit. However, the expression level and roles of KIF22 in TSCC remain to be explored.In this study, we aimed at investigating the prognostic significance of KIF22 in TSCC. Firstly, we detected the protein expression of KIF22 in TSCC tissues and the normal tissues adjacent to cancer, and we observed that patients with high expression of KIF22 had a poor prognosis, low overall survival rate, and disease-free survival rate. Then, we demonstrated the function of KIF22 in vitro and in vivo. Those data showed that KIF22 might play an important role in TSCC, and KIF22 could be considered as a potent prognostic factor in TSCC.


## 2. Materials and Methods

### 2.1. Tissue Collection and Immunohistochemical Assays

82 tissues of TSCC and adjacent normal tissues were collected from patients who underwent surgery in Tianjin First Central Hospital, and the protocol concerning human specimens was approved and the informed consent before the surgery was obtained. However, we cannot provide consent because of the Chinese language and privacy protection. According to the 2009 UICC TNM classification and the 2004 WHO/ISUP classification, the following data were retrospectively collected: age, gender, tumor stage, differentiation, clinical stage, and lymphatic invasion. No evidence of tumor metastasis was confirmed by cross-sectional imaging in all patients. Tissues were formalin-fixed and paraffin-embedded, and then 4μm sections were made. Those sections were heated in an oven at 75°C for 30 min, deparaffinized in xylene, and rehydrated in alcohol (100%, 100%, 95%, 85%, and 75%). Immunohistochemistry assays were introduced according to the specifications of immunohistochemistry assays (Cell Signaling Technology, Danvers, Massachusetts, USA). Briefly, antigen was retrieved by citric acid buffer in a microwave for 15 min and then cooled at room temperature. Endogenous peroxidase was blocked using blocking reagent for 5 min at room temperature and washed three times using PBS buffer. Then, the sections were incubated overnight at 4°C with a monoclonal mouse anti-KIF22 antibody (Thermo Fisher Scientific, Waltham, MA, USA, 1 : 200). The second day, the sections were washed three times in PBS and incubated with secondary antibody-HRP (Proteintech, Sanying, Wuhan, China, 1 : 1000) for 1 hour at room temperature, washed, and stained with diaminobenzidine (DAB, Cell Signaling Technology, Pudong, Shanghai, China) for 5 min. The images were collected by a microscope (Nikon, Tokyo, Japan).We scored for KIF22 nuclear expression based on staining area and staining intensity. We used semiquantitative results to judge the percentage of microscopically positive cells and staining intensity. The number of positive cells was <5%, 0 points; 5% to 25%, 1 point; 26% to 50%, 2 points; 51% to 75%, for 3 points; and 76% to 100%, 4 points. Positive staining intensity score was 0 for no color, 1 for light yellow, 2 for brown, and 3 for brown. The two scores are multiplied by the positive rating: 0 is negative (−), 1–4 is weakly positive (+), 5–8 is positive (++), and 9–12 is strongly positive (+++). In this study, we divided the positive staining of KIF22 expression as low (− and +) and high (+ and ++) expression.


### 2.2. Cell Culture

CAL-27 (ATCC, USA) and SCC-15 (ATCC, USA) cells were cultured with high glucose DMEM (Gibco, Waltham, Massachusetts, USA) supplemented with 10% fetal bovine serum (FBS, Gibco) or PRMI 1640 (Gibco) supplemented with 20% FBS. All cells were incubated in 5% CO2 at 37°C.


### 2.3. Knockdown of KIF22 and Stable Colony Formation

The plasmid of knockdown KIF22 and negative control plasmid were provided by the hospital. The shRNA sequence was 5′AAGCAAGATTGGAGCTACTCGTC3′. CAL-27 and SCC-15 cells were transfected with shRNA and negative control plasmid using Lipofectamine 3000 (Thermo, Waltham, Massachusetts, USA). Then, after 72 hours, shCAL-27 and shSCC-15 cells were cultured in medium with puromycin (Sigma, St. Louis, Missouri, USA, 1.5μg/ml) for two weeks to select stable colony.


### 2.4. PCR

Total RNA was isolated from cells using TRIzol reagent (Thermo, Waltham, Massachusetts, USA), and then RNA was reverse transcribed to cDNA using High Capacity cDNA Reverse Transcription Kit (Thermo, Waltham, Massachusetts, USA) according to the manufacturer’s instruction. KIF22 primer sequence: F-5′-CGGCCTTTTACCAATGAGAGC3′ and R-5′-GACCAAGCAATTCTTTCTGAGACA-3′ [18]. Gapdh primer sequence: F-5′-CGACCACTTTGTCAAGCTCA-3′ and R-5′-GGTTGAGCACAGGGTACTTTATT-3′. DNA bands were stained with ethidium bromide (Solarbio, Beijing, China, 1 ug/ml). The quantification of PCR results was done using ImageJ. Each reaction contains 25 μl of 2 × Taq Master Mix (CWBIO, Beijing, China), 2 μl of 10 μM forward primer, 2 μl of 10 μM reverse primer, 1 μl of template DNA, and 20 μl of RNase-free water. PCR conditions were as follows: predenaturation at 95°C for 3 min, followed by 35 cycles of denaturation at 95°C for 30 s, annealing at 55°C for 30 s, and extension at 72°C for 30 s and then at 72°C for 2 min.


### 2.5. Western Blot

Total proteins were collected from cells using RIPA- PMSF (Solarbio, Beijing, China, 100 : 1), added with 100μl/well in 6 wells and incubated for 30 min, centrifugated for 30 min at 4°C, and then stored at −20°C until used. 30 μg of total protein was added to 10% SDS-PAGE for separation at 90V. Then, protein bands were transferred to PVDF membrane (Solarbio, Beijing, China) at 250 mA for 130 min. The membrane was washed three times with TBST, blocked in 10% nonfat milk, and incubated overnight at 4°C with rabbit anti-KIF22 antibody (Abcam, Cambridge, UK, 1 : 2000). The second day, the membrane was washed with TBST and incubated with goat anti-rabbit antibody (Proteintech, Sanying, Wuhan, China, 1 : 10000) for 1 hour at room temperature. Finally, protein bands were detected using ECL reagent kit (Solarbio, Beijing, China) and images were collected. Protein levels of β-actin antibody (Cell Signaling Technology, Danvers, Massachusetts, USA, 1 : 1000), Ki67 (Abcam, Cambridge, UK, 1 : 2000), and PCNA (Cell Signaling Technology, Pudong, Shanghai, China 1 : 2000) were detected by western blot in a similar way.


### 2.6. Colony Formation Assays

Cells were suspended in the complete medium, and the cell density was adjusted to 100 cells/ml with complete medium. Then, 2 ml of complete medium was added to every well with 200 cells in 6-well plates and cultured at 37°C in 5% CO2 for two weeks. Finally, cells were fixed by 4% paraformaldehyde for 10 minutes and stained with 0.1% crystal violet. The number of colonies was counted manually using the microscope.


### 2.7. MTT Assays

MTT assays were introduced into 96-well plates containing 100μl complete medium (3000 cells/well) and incubated for three days at 37°C in 5% CO2. After three days, the medium was replaced by 20 μl MTT solution (Solarbio, Beijing, China, 5 mg/ml) and incubated for 4 hours at 37°C. Then, MTT solution was removed and 150 μl DMSO was added (Solarbio, Beijing, China) to every well for 10 minutes at room temperature to solubilize the formazan crystals. The optical density (OD) was detected by using a spectrophotometer at 570 nm.


### 2.8. Animal Study

Nude Balb/c mice (6–8 weeks old, weighing 18–22 g) were provided by Shanghai Laboratory Animal Center. CAL-27 and shCAL-27 cells (5 × 106 cells/mice) were suspended and transplanted subcutaneously into the armpit of nude mice. Tumor length and width were measured every three days, calculating tumor volume (V = 0.5 × L × W [2], V: volume, L: length, and W: width) [19]. After 29 days, all mice were killed, and xenograft tumors were removed for examination and fixed with 4% paraformaldehyde. Protein expression level of KIF22 was detected by western blot and immunohistochemical staining in xenograft tumors.


### 2.9. Statistical Analysis

Data in this study were analyzed with SPSS 22.0 software. Quantitative data are presented as the mean ± standard deviation (SD), and Student’st-test was used for comparison between two groups. The association between immunohistochemical results and patient’s information was evaluated using χ2 tests. The connections between KIF22 expression level and patients’ survival time after surgery were performed by Kaplan–Meier (KM) method. The categorical data were analyzed by chi-square test. A value of P<0.05 was considered as statistical significance.


## 2.1. Tissue Collection and Immunohistochemical Assays

82 tissues of TSCC and adjacent normal tissues were collected from patients who underwent surgery in Tianjin First Central Hospital, and the protocol concerning human specimens was approved and the informed consent before the surgery was obtained. However, we cannot provide consent because of the Chinese language and privacy protection. According to the 2009 UICC TNM classification and the 2004 WHO/ISUP classification, the following data were retrospectively collected: age, gender, tumor stage, differentiation, clinical stage, and lymphatic invasion. No evidence of tumor metastasis was confirmed by cross-sectional imaging in all patients. Tissues were formalin-fixed and paraffin-embedded, and then 4μm sections were made. Those sections were heated in an oven at 75°C for 30 min, deparaffinized in xylene, and rehydrated in alcohol (100%, 100%, 95%, 85%, and 75%). Immunohistochemistry assays were introduced according to the specifications of immunohistochemistry assays (Cell Signaling Technology, Danvers, Massachusetts, USA). Briefly, antigen was retrieved by citric acid buffer in a microwave for 15 min and then cooled at room temperature. Endogenous peroxidase was blocked using blocking reagent for 5 min at room temperature and washed three times using PBS buffer. Then, the sections were incubated overnight at 4°C with a monoclonal mouse anti-KIF22 antibody (Thermo Fisher Scientific, Waltham, MA, USA, 1 : 200). The second day, the sections were washed three times in PBS and incubated with secondary antibody-HRP (Proteintech, Sanying, Wuhan, China, 1 : 1000) for 1 hour at room temperature, washed, and stained with diaminobenzidine (DAB, Cell Signaling Technology, Pudong, Shanghai, China) for 5 min. The images were collected by a microscope (Nikon, Tokyo, Japan).We scored for KIF22 nuclear expression based on staining area and staining intensity. We used semiquantitative results to judge the percentage of microscopically positive cells and staining intensity. The number of positive cells was <5%, 0 points; 5% to 25%, 1 point; 26% to 50%, 2 points; 51% to 75%, for 3 points; and 76% to 100%, 4 points. Positive staining intensity score was 0 for no color, 1 for light yellow, 2 for brown, and 3 for brown. The two scores are multiplied by the positive rating: 0 is negative (−), 1–4 is weakly positive (+), 5–8 is positive (++), and 9–12 is strongly positive (+++). In this study, we divided the positive staining of KIF22 expression as low (− and +) and high (+ and ++) expression.


## 2.2. Cell Culture

CAL-27 (ATCC, USA) and SCC-15 (ATCC, USA) cells were cultured with high glucose DMEM (Gibco, Waltham, Massachusetts, USA) supplemented with 10% fetal bovine serum (FBS, Gibco) or PRMI 1640 (Gibco) supplemented with 20% FBS. All cells were incubated in 5% CO2 at 37°C.


## 2.3. Knockdown of KIF22 and Stable Colony Formation

The plasmid of knockdown KIF22 and negative control plasmid were provided by the hospital. The shRNA sequence was 5′AAGCAAGATTGGAGCTACTCGTC3′. CAL-27 and SCC-15 cells were transfected with shRNA and negative control plasmid using Lipofectamine 3000 (Thermo, Waltham, Massachusetts, USA). Then, after 72 hours, shCAL-27 and shSCC-15 cells were cultured in medium with puromycin (Sigma, St. Louis, Missouri, USA, 1.5μg/ml) for two weeks to select stable colony.


## 2.4. PCR

Total RNA was isolated from cells using TRIzol reagent (Thermo, Waltham, Massachusetts, USA), and then RNA was reverse transcribed to cDNA using High Capacity cDNA Reverse Transcription Kit (Thermo, Waltham, Massachusetts, USA) according to the manufacturer’s instruction. KIF22 primer sequence: F-5′-CGGCCTTTTACCAATGAGAGC3′ and R-5′-GACCAAGCAATTCTTTCTGAGACA-3′ [18]. Gapdh primer sequence: F-5′-CGACCACTTTGTCAAGCTCA-3′ and R-5′-GGTTGAGCACAGGGTACTTTATT-3′. DNA bands were stained with ethidium bromide (Solarbio, Beijing, China, 1 ug/ml). The quantification of PCR results was done using ImageJ. Each reaction contains 25 μl of 2 × Taq Master Mix (CWBIO, Beijing, China), 2 μl of 10 μM forward primer, 2 μl of 10 μM reverse primer, 1 μl of template DNA, and 20 μl of RNase-free water. PCR conditions were as follows: predenaturation at 95°C for 3 min, followed by 35 cycles of denaturation at 95°C for 30 s, annealing at 55°C for 30 s, and extension at 72°C for 30 s and then at 72°C for 2 min.


## 2.5. Western Blot

Total proteins were collected from cells using RIPA- PMSF (Solarbio, Beijing, China, 100 : 1), added with 100μl/well in 6 wells and incubated for 30 min, centrifugated for 30 min at 4°C, and then stored at −20°C until used. 30 μg of total protein was added to 10% SDS-PAGE for separation at 90V. Then, protein bands were transferred to PVDF membrane (Solarbio, Beijing, China) at 250 mA for 130 min. The membrane was washed three times with TBST, blocked in 10% nonfat milk, and incubated overnight at 4°C with rabbit anti-KIF22 antibody (Abcam, Cambridge, UK, 1 : 2000). The second day, the membrane was washed with TBST and incubated with goat anti-rabbit antibody (Proteintech, Sanying, Wuhan, China, 1 : 10000) for 1 hour at room temperature. Finally, protein bands were detected using ECL reagent kit (Solarbio, Beijing, China) and images were collected. Protein levels of β-actin antibody (Cell Signaling Technology, Danvers, Massachusetts, USA, 1 : 1000), Ki67 (Abcam, Cambridge, UK, 1 : 2000), and PCNA (Cell Signaling Technology, Pudong, Shanghai, China 1 : 2000) were detected by western blot in a similar way.


## 2.6. Colony Formation Assays

Cells were suspended in the complete medium, and the cell density was adjusted to 100 cells/ml with complete medium. Then, 2 ml of complete medium was added to every well with 200 cells in 6-well plates and cultured at 37°C in 5% CO2 for two weeks. Finally, cells were fixed by 4% paraformaldehyde for 10 minutes and stained with 0.1% crystal violet. The number of colonies was counted manually using the microscope.


## 2.7. MTT Assays

MTT assays were introduced into 96-well plates containing 100μl complete medium (3000 cells/well) and incubated for three days at 37°C in 5% CO2. After three days, the medium was replaced by 20 μl MTT solution (Solarbio, Beijing, China, 5 mg/ml) and incubated for 4 hours at 37°C. Then, MTT solution was removed and 150 μl DMSO was added (Solarbio, Beijing, China) to every well for 10 minutes at room temperature to solubilize the formazan crystals. The optical density (OD) was detected by using a spectrophotometer at 570 nm.


## 2.8. Animal Study

Nude Balb/c mice (6–8 weeks old, weighing 18–22 g) were provided by Shanghai Laboratory Animal Center. CAL-27 and shCAL-27 cells (5 × 106 cells/mice) were suspended and transplanted subcutaneously into the armpit of nude mice. Tumor length and width were measured every three days, calculating tumor volume (V = 0.5 × L × W [2], V: volume, L: length, and W: width) [19]. After 29 days, all mice were killed, and xenograft tumors were removed for examination and fixed with 4% paraformaldehyde. Protein expression level of KIF22 was detected by western blot and immunohistochemical staining in xenograft tumors.


## 2.9. Statistical Analysis

Data in this study were analyzed with SPSS 22.0 software. Quantitative data are presented as the mean ± standard deviation (SD), and Student’st-test was used for comparison between two groups. The association between immunohistochemical results and patient’s information was evaluated using χ2 tests. The connections between KIF22 expression level and patients’ survival time after surgery were performed by Kaplan–Meier (KM) method. The categorical data were analyzed by chi-square test. A value of P<0.05 was considered as statistical significance.


## 3. Results

### 3.1. KIF22 Is Overexpressed in TSCC and Associated with Poor Prognosis

To study the role of KIF22 in TSCC, tumor tissues and disease information of 82 patients with TSCC were collected. Protein expression level of KIF22 in high-grade, low-grade, and adjacent normal tissues in TSCC by was analyzed by immunohistochemical staining (Figures1(a) and 1(b)). The results showed that the expression level of KIF22 was different in carcinoma and in adjacent normal tissues. In addition, KIF22 had a low expression level in adjacent normal tissues compared with carcinoma (positive rate: 62/82 vs. 30/82, χ2 = 9.557, P = 0.002 < 0.05). By analyzing all results of immunohistochemical staining and patient’s information, including age, gender, tumor stage, differentiation, clinical stage, and lymphatic metastasis, we could draw a conclusion that the expression level of KIF22 was associated with tumor stage (P=0.013), clinical stage (P=0.034), and lymph node metastasis (P=0.015), but had little to do with age, gender, or differentiation (P>0.05, respectively) (Table 1). Patients with high expression of KIF22 had a poor prognosis and overall survival rate, and the disease-free survival rate was low compared with low expression (Figure 1(c)). The above data indicated that KIF22 might play an important role in TSCC and associated with poor prognosis.Figure 1
KIF22 is overexpressed in TSCC and associated with poor prognosis. (a) Representative images of KIF22 expression level in patients with TSCC by immunohistochemical staining. The expression level of KIF22 was different in patients. (b) Immunohistochemical staining of KIF22 in adjacent normal tissues. (c) Overall survival rate and disease-free survival rate of patients with a high or low expression level of KIF22, respectively.
(a)
(b)
(c)Table 1
Relationships of KIF22 and clinicopathological characteristics in 82 patients with tongue squamous cell carcinoma.
Feature
Alln = 82
KIF22 expression
χ
2
P
Low
High
n = 42
n = 40
Age (years)
2.905
0.088
<65
54
24
30
≥65
28
18
10
Gender
1.179
0.278
Male
46
26
20
Female
36
16
20
Tumor stage
6.129
0.013∗
T1-2
36
24
12
T3-4
46
18
28
Differentiation
3.241
0.072
Low
24
16
8
High
58
26
32
Clinical stage
4.518
0.034∗
I-II
30
20
10
III-IV
52
22
30
Lymphatic metastasis
5.896
0.015∗
Yes
34
12
22
No
48
30
18


### 3.2. Stable Clone of Suppression of KIF22 in CAL-27 and SCC-15 Cells with shRNA

To further study the role of KIF22 in TSCC, stable cell clone of suppression of KIF22 in CAL-27 and SCC-15 cells was established by short hairpin RNA. CAL-27 cells were transfected with the plasmid containing shRNA, and negative control cells were transfected with control plasmid containing random sequence. SCC-15 cells were transfected in the same way. Then, the transfected cells were incubated in complete medium with puromycin until negative cells were killed to establish stable clone. As shown in Figure2(a), the mRNA expression level of CAL-27 cells transfected with shRNA was lower than that of control cells (P<0.05). The result of the other cells, SCC-15 cells and shSCC-15 cells, was similar (P<0.05). Then, the protein level of KIF22 was detected using western blot in CAL-27, shCAL-27, SCC-15, and shSCC-15 cells. As shown in Figure 2(b), KIF22 had a low expression in protein level when transfected with shRNA in CAL-27 and SCC-15 cells (P<0.05, respectively).Figure 2
Stable clone of suppression of KIF22 in CAL-27 cells and SCC-15 cells with shRNA. (a) KIF22 mRNA expression level in CAL-27cells and SCC-15 cells transfected with shRNA to knockdown KIF22, respectively. (b) The protein expression level of KIF22 in CAL-27 cells and SCC-15 cells was detected using western blot and quantified by ImageJ∗P<0.05.
(a)
(b)


### 3.3. Suppression of KIF22 Inhibits Proliferation in CAL-27 Cells and SCC-15 Cells

In previous reports, suppression of KIF22 inhibits cell proliferation in cancer cell [17]. However, there was no report about KIF22 in TSCC. To observe the role of KIF22 in this cancer, colony formation assays were performed in CAL-27 and SCC-15 cells, and cells transfected with shRNA showed that knockdown of KIF22 decreased colony formation ability (Figure 3(a)). Incubating for 2 weeks, compared with negative control cells, shCAL-27 and shSCC-15 cells displayed fewer colonies (P<0.05). To further assess cell proliferation triggered by KIF22, MTT assays were introduced in above cells. As shown in Figure 3(b), the result was similar with colony formation assays, shCAL-27 had a low cell proliferation compared with negative control cells, and SCC-15 cells had the same result (P<0.05). In previous studies, Ki67 [20, 21] and PCNA [22, 23] were accepted protein markers associated with cell proliferation. Protein expression levels of Ki67 (Figure 3(c)) and PCNA (Figure 3(d)) were detected by western blot in cells transfected with shRNA and negative control cells (CAL-27, shCAL-27, SCC-15, and shSCC-15), showing that suppression of KIF22 led to a low expression of Ki67 and PCNA (P<0.05, respectively). Those data indicated that KIF22 might play an important role in cell proliferation in TSCC.Figure 3
Suppression of KIF22 inhibited proliferation in CAL-27 cells and SCC-15 cells. (a) Representative images of colony formation assays of CAL-27 cells transfected with shRNA (shCAL-27) and SCC-15 cells transfected with shRNA (shSCC-15) (left). Qualification result of assays (right). (b) MTT assays of CAL-27 cells, shCAL-27 cells (left) and TCA18133 cell, shTCA18133 cells. (c) Protein expression level of ki67 in CAL-27 cells and shCAL-27 cells. Same detection in SCC-15 cells and shSCC-15 cells. (d) PCNA protein expression level in CAL-27 cells and shCAL-27 cells. Same detection in TCA18133 cells and shTCA18133 cells. Data represent mean ± SD.∗P<0.05.
(a)
(b)
(c)
(d)


### 3.4. Knockdown of KIF22 Inhibits Xenograft Tumor Growth

The above data showed that KIF22 affected cell proliferation in vitro. Then, to further study the role of KIF22 in TSCC, in vivo experiments were performed to observe tumor growth in mice. CAL-27 cells and shCAT-27 (5 × 106 cells) were injected subcutaneously into the armpit of mice, and tumor size was measured and tumor volume was calculated every five days. As shown in Figure 4(a), xenograft tumor volume from CAL-27 cells was smaller than those from shCAT-27 cells at every checkpoint. After 30 days, all tumors were removed from mice and KIF22 protein expression level was observed by western blot in tissues of xenograft tumors, showing that tumors from CAL-27 cells had higher expression than shCAL-27 (Figure 4(b)). Immunohistochemical staining had a similar result (Figure 4(c)).Figure 4
Knockdown KIF22 inhibited xenograft tumor growth. (a) Tumor growth curve in nude mice (left). CAL-27 cells and shCAT-27 were injected subcutaneously into the armpit of mice, tumor size was measured every 3 days, and tumor volume was calculated. Representative images of xenograft tumor (right). (b) Protein expression level of KIF22 in xenograft tumor by western blot. (c) Representative images of immunohistochemical staining of KIF22 in xenograft tumors (top) and qualification (bottom).
(a)
(b)
(c)


## 3.1. KIF22 Is Overexpressed in TSCC and Associated with Poor Prognosis

To study the role of KIF22 in TSCC, tumor tissues and disease information of 82 patients with TSCC were collected. Protein expression level of KIF22 in high-grade, low-grade, and adjacent normal tissues in TSCC by was analyzed by immunohistochemical staining (Figures1(a) and 1(b)). The results showed that the expression level of KIF22 was different in carcinoma and in adjacent normal tissues. In addition, KIF22 had a low expression level in adjacent normal tissues compared with carcinoma (positive rate: 62/82 vs. 30/82, χ2 = 9.557, P = 0.002 < 0.05). By analyzing all results of immunohistochemical staining and patient’s information, including age, gender, tumor stage, differentiation, clinical stage, and lymphatic metastasis, we could draw a conclusion that the expression level of KIF22 was associated with tumor stage (P=0.013), clinical stage (P=0.034), and lymph node metastasis (P=0.015), but had little to do with age, gender, or differentiation (P>0.05, respectively) (Table 1). Patients with high expression of KIF22 had a poor prognosis and overall survival rate, and the disease-free survival rate was low compared with low expression (Figure 1(c)). The above data indicated that KIF22 might play an important role in TSCC and associated with poor prognosis.Figure 1
KIF22 is overexpressed in TSCC and associated with poor prognosis. (a) Representative images of KIF22 expression level in patients with TSCC by immunohistochemical staining. The expression level of KIF22 was different in patients. (b) Immunohistochemical staining of KIF22 in adjacent normal tissues. (c) Overall survival rate and disease-free survival rate of patients with a high or low expression level of KIF22, respectively.
(a)
(b)
(c)Table 1
Relationships of KIF22 and clinicopathological characteristics in 82 patients with tongue squamous cell carcinoma.
Feature
Alln = 82
KIF22 expression
χ
2
P
Low
High
n = 42
n = 40
Age (years)
2.905
0.088
<65
54
24
30
≥65
28
18
10
Gender
1.179
0.278
Male
46
26
20
Female
36
16
20
Tumor stage
6.129
0.013∗
T1-2
36
24
12
T3-4
46
18
28
Differentiation
3.241
0.072
Low
24
16
8
High
58
26
32
Clinical stage
4.518
0.034∗
I-II
30
20
10
III-IV
52
22
30
Lymphatic metastasis
5.896
0.015∗
Yes
34
12
22
No
48
30
18


## 3.2. Stable Clone of Suppression of KIF22 in CAL-27 and SCC-15 Cells with shRNA

To further study the role of KIF22 in TSCC, stable cell clone of suppression of KIF22 in CAL-27 and SCC-15 cells was established by short hairpin RNA. CAL-27 cells were transfected with the plasmid containing shRNA, and negative control cells were transfected with control plasmid containing random sequence. SCC-15 cells were transfected in the same way. Then, the transfected cells were incubated in complete medium with puromycin until negative cells were killed to establish stable clone. As shown in Figure2(a), the mRNA expression level of CAL-27 cells transfected with shRNA was lower than that of control cells (P<0.05). The result of the other cells, SCC-15 cells and shSCC-15 cells, was similar (P<0.05). Then, the protein level of KIF22 was detected using western blot in CAL-27, shCAL-27, SCC-15, and shSCC-15 cells. As shown in Figure 2(b), KIF22 had a low expression in protein level when transfected with shRNA in CAL-27 and SCC-15 cells (P<0.05, respectively).Figure 2
Stable clone of suppression of KIF22 in CAL-27 cells and SCC-15 cells with shRNA. (a) KIF22 mRNA expression level in CAL-27cells and SCC-15 cells transfected with shRNA to knockdown KIF22, respectively. (b) The protein expression level of KIF22 in CAL-27 cells and SCC-15 cells was detected using western blot and quantified by ImageJ∗P<0.05.
(a)
(b)


## 3.3. Suppression of KIF22 Inhibits Proliferation in CAL-27 Cells and SCC-15 Cells

In previous reports, suppression of KIF22 inhibits cell proliferation in cancer cell [17]. However, there was no report about KIF22 in TSCC. To observe the role of KIF22 in this cancer, colony formation assays were performed in CAL-27 and SCC-15 cells, and cells transfected with shRNA showed that knockdown of KIF22 decreased colony formation ability (Figure 3(a)). Incubating for 2 weeks, compared with negative control cells, shCAL-27 and shSCC-15 cells displayed fewer colonies (P<0.05). To further assess cell proliferation triggered by KIF22, MTT assays were introduced in above cells. As shown in Figure 3(b), the result was similar with colony formation assays, shCAL-27 had a low cell proliferation compared with negative control cells, and SCC-15 cells had the same result (P<0.05). In previous studies, Ki67 [20, 21] and PCNA [22, 23] were accepted protein markers associated with cell proliferation. Protein expression levels of Ki67 (Figure 3(c)) and PCNA (Figure 3(d)) were detected by western blot in cells transfected with shRNA and negative control cells (CAL-27, shCAL-27, SCC-15, and shSCC-15), showing that suppression of KIF22 led to a low expression of Ki67 and PCNA (P<0.05, respectively). Those data indicated that KIF22 might play an important role in cell proliferation in TSCC.Figure 3
Suppression of KIF22 inhibited proliferation in CAL-27 cells and SCC-15 cells. (a) Representative images of colony formation assays of CAL-27 cells transfected with shRNA (shCAL-27) and SCC-15 cells transfected with shRNA (shSCC-15) (left). Qualification result of assays (right). (b) MTT assays of CAL-27 cells, shCAL-27 cells (left) and TCA18133 cell, shTCA18133 cells. (c) Protein expression level of ki67 in CAL-27 cells and shCAL-27 cells. Same detection in SCC-15 cells and shSCC-15 cells. (d) PCNA protein expression level in CAL-27 cells and shCAL-27 cells. Same detection in TCA18133 cells and shTCA18133 cells. Data represent mean ± SD.∗P<0.05.
(a)
(b)
(c)
(d)


## 3.4. Knockdown of KIF22 Inhibits Xenograft Tumor Growth

The above data showed that KIF22 affected cell proliferation in vitro. Then, to further study the role of KIF22 in TSCC, in vivo experiments were performed to observe tumor growth in mice. CAL-27 cells and shCAT-27 (5 × 106 cells) were injected subcutaneously into the armpit of mice, and tumor size was measured and tumor volume was calculated every five days. As shown in Figure 4(a), xenograft tumor volume from CAL-27 cells was smaller than those from shCAT-27 cells at every checkpoint. After 30 days, all tumors were removed from mice and KIF22 protein expression level was observed by western blot in tissues of xenograft tumors, showing that tumors from CAL-27 cells had higher expression than shCAL-27 (Figure 4(b)). Immunohistochemical staining had a similar result (Figure 4(c)).Figure 4
Knockdown KIF22 inhibited xenograft tumor growth. (a) Tumor growth curve in nude mice (left). CAL-27 cells and shCAT-27 were injected subcutaneously into the armpit of mice, tumor size was measured every 3 days, and tumor volume was calculated. Representative images of xenograft tumor (right). (b) Protein expression level of KIF22 in xenograft tumor by western blot. (c) Representative images of immunohistochemical staining of KIF22 in xenograft tumors (top) and qualification (bottom).
(a)
(b)
(c)


## 4. Discussion

To the best of our knowledge, this is the first study of KIF22 in TSCC. In previous reports, it was indicated that KIF22 had a high expression in several cancer tissues and was associated with proliferation. Yu et al. detected mRNA and protein expression levels of KIF22 in 62 primary breast cancer tissues and paired adjacent normal tissues, showing that KIF22, in both mRNA and protein, was upregulated in primary breast cancer compared with adjacent tissues [17]. Then, to further study the relationship between KIF22 and cancer development, they analyzed KIF22 in several cancers in Oncomine database and confirmed that KIF22 had a high expression in ovarian cancer, lung cancer, and cervical cancer [17]. The above data suggested that KIF22 was overexpressed in several tumors and associated with poor prognosis. In our study, 82 tissues of TSCC and adjacent normal tissues were collected to detect the expression level of KIF22. By analyzing KIF22 expression level in cancer tissues with patients' information, we observed that expression level of KIF22 was associated with tumor stage, clinical stage, and metastasis (P<0.05, respectively), but there was not an apparent correlation with differentiation (P>0.05).In the previous reports, kinesin family played an essential role in mitosis [14, 24–26] and changed the expression level of cancer cells contributing to proliferation, such as KIF18A [27], KIF26B [15], KIF14 [28−30], and EG5 [31−33]. Specific inhibitors of EG5 are in phase I or phase II clinical trials [34, 35]. Yu et al. reported that cells knockdown KIF22 display a fast S to G2/M phase but slow mitotic exit [17]. Similarly, our study showed that suppression of KIF22 inhibited proliferation and xenograft tumors. KIF22 is a novel transcriptional targeting CDC25C and negatively regulates CDC25C in mRNA and protein levels. KIF22 exists several phosphorylated sites, including Ser427 and Thr463 [36], and Thr463 is conserved in many species [37, 38]. Ohsugi et al. reported that the phosphorylation of KIF22 at Thr463 inhibited KIF22 connected to microtubules but increased the affinity to chromosomes [36]: overexpressed KIF22 in cancers increased cell proliferation by inhibiting CDC25C, increasing mitotic exit.To further investigate the role of KIF22 in TSCC, we established stable KIF22 suppression in CAL-27 and SCC-15 cells, which were derived from human TSCC. In cell proliferation assays, we observed that knockdown KIF22 inhibited colony formation and cell growth. In previous reports, Ki67 and PCNA were protein markers to detect cell proliferation in cells, so we evaluated the expression level of Ki67 and PCNA in CAL-27 and SCC-15 cells compared with shCAL-27 and shSCC-15 cells and found that Ki67 and PCNA had low expression in cells transfected with shRNA. Those data indicated that suppression of KIF22 inhibited cell proliferation in vitro. Although the results are different, we also could use similar methods to explore the mechanism [39–41].In human breast cancer cell line, MDA-MB-435, shcontrol cells and shKIF22 cells were inoculated into the mammary fat pads of nude mice. After 7 weeks, the result showed that xenograft tumors from shKIF22 cells had small tumor volume [17]. Similarly, in our study, the animal experiments were designed to verify the role in vivo. As shown in Figures 4(a) and 4(b), suppression of KIF22 in cells decreased xenograft tumor growth in nude mice. This result was similar with cellular level. Miki et al. reported that KIF22 was regulated by SIAH-1 [14]. A research reported a novel pathway between KIF22 and EGFR, CAR. KIF22 bound to microtubules which were important in receptor traffic, including EGFR [42, 43]. KIF22 regulated microtubule stability and upregulated EGFR signaling which promoted CAR phosphorylation and relocalization at plasma membrane to increase cell division [44].In the process of tumorigenesis, multiple factors interact to promote tumorigenesis and development. In a multicenter cohort, Jin reported that the expression of KDM4A was an independent predictor factor for the survival time in TSCC and significantly associated with lymph node metastasis and pathological stages. This finding was validated by TCGA data [45]. Arita et al. analyzed FBXW7 expression between tumor tissues and paired adjacent normal tissues from 15 patients and 110 patients with TSCC, showing that FBXW7 was significantly decreased in cancer tissues compared with adjacent normal tissues [46]. In our study, suppression effect of KIF22 was observed, and then downstream pathways should be detected.The limitation of this study is that this is a retrospective research with a small number of cases in single center. We observed the role of KIF22 in TSCC by only suppression of KIF22 in vitro and in vivo. The overexpression of KIF22 should be conducted to further observer the role in vitro and in vivo.In summary, this is the first study of KIF22 in TSCC, and we observed that KIF22 was upregulated in tissues of TSCC and associated with poor prognosis. Inhibition of KIF22 suppressed cell proliferation and xenograft tumors. Thus, KIF22 might be a target for TSCC therapy.



---

*Source: 6387545-2020-01-22.xml*