Antitumor‑ and apoptosis‑inducing effects of pomolic acid against SK‑MEL‑2 human malignant melanoma cells are mediated via inhibition of cell migration and sub‑G1 cell cycle arrest
Authors: Hong-Xia Yan
Tian-Hang Li
Journal: Molecular Medicine Reports (2017)
Discipline: CLINICAL MEDICINE
Keywords: Malignant melanoma; pomolic acid; antitumor effects; apoptosis; cell migration
Affiliations: Department of Dermatology, Jining First People's Hospital, Jining, Shandong 272000, P.R. China

Abstract:  Malignant melanoma is the leading cause of mortality among the skin‑associated diseases because of its highly metastatic nature and lethality. The aim of the present study was to evaluate antitumor and apoptosis effects of pomolic acid, a pentacyclic triterpene, against SK‑MEL‑2 human malignant melanoma cells. Its effect on cell migration and cell cycle arrest were also studied. An MTT assay was used to assess the cell cytotoxicity effects induced by pomolic acid. Fluorescence microscopy using acridine orange/propidium iodide and Hoechst 33342 staining, along with transmission electron microscopy (TEM), was used to study the effects of pomolic acid on apoptosis induction in these cells. The effects of pomolic acid on cell migration were studied using an in vitro wound healing assay. The effects of pomolic acid on cell cycle phase distribution were evaluated by flow cytometry using propidium iodide as fluorescent probe. The results revealed that pomolic acid induced significant dose‑ and time‑dependent antiproliferative effects in SK‑MEL‑2 human malignant melanoma cells, with IC50 values of 110.3, 88.1 and 79.3 µM after 24, 48 and 72 h, respectively. Pomolic acid‑treated cells exhibited red fluorescence, and the intensity of this fluorescence increased in a dose‑dependent manner, indicating apoptosis induction. After the cells were treated with 25, 75 and 150 µM pomolic acid, significant morphological alterations characteristic of apoptosis were observed by TEM, including loss of microvilli, a damaged plasma membrane, damaged cellular organelles and enlarged lysosomes. Pomolic acid also led to sub‑G1 cell cycle arrest, and inhibited cancer cell migration in a dose‑dependent manner. These results implicate pomolic acid as a potential therapeutic agent for the treatment of malignant melanoma. 

Retracted: Yes

PubPeer comments:
 Figure 4.  Pomolic acid induces apoptosis in SK-MEL-2 human malignant melanoma cells. The cells were treated with (A) 0, (B) 25, (C) 75 and (D) 150 u00b5M pomolic acid for 48 h. The white arrows represent cells, which have undergone apoptosis. The images were captured using a fluorescence microscope . A, B and C are essentially the same image, with 90-deg rotations, and minor alterations. D contains repeated cells. ![] , 
 Fig 5. Transmission electron microscopy micrographs of SK-MEL-2 human melanoma cells. Cells were treated with (A) 0, (B) 25, (C) 75 and (D) 150 u00b5M pomolic acid for 72 h. (A) Untreated control human melanoma cells revealing characteristic cell ultrastructure with intact plasma membrane. Magnification, x5,000. (B) and (C) reveal early stages of apoptosis (magnification, x5,000) while (D) depicts late apoptotic stage, characterized by a damaged plasma membrane, damaged cell organelles and enlarged lysosomes ![file] (A) and (C) are the same cell, with different internal modifications. All the images reveal repeated areas. , 
 Figure 8.  Pomolic acid induces sub-G1 cell cycle arrest in SK-MEL-2 human malignant melanoma cells. The cells were treated with (A) 0, (B) 25, (C) 75 and (D) 150 u00b5M pomolic acid for 48 h and then analyzed by flow cytometry using propidium iodide as fluorescent probe. ![file] And Fig 7, for the sake of completeness. ![file] , 
 Also of interest: Fig 6. I have marked some internal repetitions. ![] , 
 Retracted [28 April 2021] .  Following the publication of the above paper, a concerned reader drew to the Editor s attention that several figures (Figs. 3u20118 inclusive) contained apparent anomalies, including repeated patternings of data within the same figure panels. After having conducted an independent investigation in the Editorial Office, the Editor of *Molecular Medicine Reports* has determined that the above paper should be retracted from the Journal on account of a lack of confidence concerning the originality and the authenticity of the data. The authors were asked for an explanation to account for these concerns, but the Editorial Office never received any reply. The Editor regrets any inconvenience that has been caused to the readership of the Journal. ,