Lin28A promotes the proliferation and stemness of lung cancer cells via the activation of mitogen-activated protein kinase pathway dependent on microRNA let-7c
Authors: Jinpu Yu
Yingnan Ye
Xiao Zhang
Rui Zhang
Pengpeng Liu
Journal: Annals of Translational Medicine (2021)
Discipline: CLINICAL MEDICINE
Keywords: Lin28A; MAPK pathway; cancer stemness; let-7c; lung cancer.
Affiliations: Cancer Molecular Diagnostics Core, Tianjin Medical University Cancer Institute & Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy, Key Laboratory of Cancer Immunology and Biotherapy, Tianjin, China.

Abstract:  Background: Among patients with lung cancer, metastatic and relapsed cases account for the largest proportion of disease-associated deaths. Tumor metastasis and relapse are believed to originate from cancer stem cells (CSCs), which have the capacity to be highly proliferative and invasive. In our previous studies, we established a conditional basement membrane extract-based (BME-based) 3-dimensional (3D) culture system to mimic the tumor growth environment in vivo and further amplified lung cancer stem cells (LCSCs) in our system. However, the molecular mechanisms of LCSC amplification and development in our 3D culture system have not been fully uncovered. Method: We established the conditional 3D culture system to amplify LCSCs in other lung cancer cell lines, followed by examining the expression of Lin28A and let-7 microRNAs in them. We also explored the expression of Lin28A and let-7 microRNAs in LCSCs from clinical lung cancer tissue samples and even analyzed the correlation of Lin28A/let-7c and patients' survival outcomes. We further constructed A549 cells either knockdown of Lin28A or overexpression of let-7c, followed by investigating stemness marker gene expression, and stemness phenotypes including mammosphere culture, cell migration and invasion in vitro, as well as tumorigenicity in vivo. Results: Here, we observed that Lin28A/let-7c was dysregulated in LCSCs in both the 3D culture system and lung cancer tissues. Further, the abnormal expression of Lin28A/let-7c was correlated with poor survival outcomes. Via the construction of A549 cells with let-7c over-expression, we found that let-7c inhibited the maintenance of LCSC properties, while the results of Lin28A knockdown showed that Lin28A played a critical role in the enrichment and proliferation of LCSCs via mitogen-activated protein kinase (MAPK) signaling pathway. Importantly, we found that LCSCs with knockdown of Lin28A or over-expression of let-7c exhibited inhibited carcinogenesis and disrupted expansion in vivo. Conclusions: Our study uncovered the functions and mechanisms of the Lin28A/let-7c/MAPK signaling pathway in promoting the proliferation and cancer stemness of LCSCs, which might be a potential therapeutic target for reducing and even eliminating LCSCs in the future. 

Retracted: No

PubPeer comments:
 I noticed that there are duplicated images in the articles. Figure 4G and Figure 5G, Two paired of images seem come from the same original pictures, marked red and green respectively. Although the author changed the color of Fig 4G and Fig 5G, it is still very clear that the images are duplicated. ![file] , 
 Dear Roseum, We appreciate your comment on the article u201cLin28A promotes the proliferation and stemness of lung cancer cells via the activation of mitogen-activated protein kinase pathway dependent on microRNA let-7cu201d. Referring to the same cell invasion images of A549-3D+F in Figure 4G and 5G, they indeed represented the identical experimental group in the study which were cultured in the conditional 3D system treated with growth factors. We repeated the experiment in triplicate (invasive cell numbers in A549-3D+F group: 304, 341, 371) and took the representative picture of A549-3D+F group to show in Figure 4G and 5G. Referring to the overlap of the image of A549-3D+Fsh-Lin28A in Figure 4G and the image of A549-3D+FOV-let7c in Figure 5G, we carefully check all raw data and original images. All cell invasion experiments included in Figure 4G and 5G were conducted simultaneously in one batch, which included 5 groups in total: A549-2D, A549-3D, A549-3D+F, A549-3D+Fsh-Lin28A and A549-3D+FOV-let7c. One image of A549-3D+Fsh-Lin28A group which was wrongly renamed as A549-3D+FOV-let7c was misused by accident. We have applied the right image of A549-3D+FOV-let7c to reassemble Figure 5G. We regret for the unintentional error made during the assembly of this figure, and this correction dose not adversely affect the interpretation of data or overall conclusions reported in the study. We would like to send the correction request to the editorial of ATM and apologize for any inconvenience caused. ,