Novel Pactamycin Analogs Induce p53 Dependent Cell-Cycle Arrest at S-Phase in Human Head and Neck Squamous Cell Carcinoma (HNSCC) Cells.

Abstract

Pactamycin, although putatively touted as a potent antitumor agent, has never been used as an anticancer drug due to its high cytotoxicity. In this study, we characterized the effects of two novel biosynthetically engineered analogs of pactamycin, de-6MSA-7-demethyl-7-deoxypactamycin (TM-025) and 7-demethyl-7-deoxypactamycin (TM-026), in head and neck squamous cell carcinoma (HNSCC) cell lines SCC25 and SCC104. Both TM-025 and TM-026 exert growth inhibitory effects on HNSCC cells by inhibiting cell proliferation. Interestingly, unlike their parent compound pactamycin, the analogs do not inhibit synthesis of nascent protein in a cell-based assay. Furthermore, they do not induce apoptosis or autophagy in a dose- or a time-dependent manner, but induce mild senescence in the tested cell lines. Cell cycle analysis demonstrated that both analogs significantly induce cell cycle arrest of the HNSCC cells at S-phase resulting in reduced accumulation of G2/M-phase cells. The pactamycin analogs induce expression of cell cycle regulatory proteins including master regulator p53, its downstream target p21Cip1/WAF1, p27kip21, p19, cyclin E, total and phospho Cdc2 (Tyr15) and Cdc25C. Besides, the analogs mildly reduce cyclin D1 expression without affecting expression of cyclin B, Cdk2 and Cdk4. Specific inhibition of p53 by pifithrin-α reduces the percentage of cells accumulated in S-phase, suggesting contribution of p53 to S-phase increase. Altogether, our results demonstrate that Pactamycin analogs TM-025 and TM-026 induce senescence and inhibit proliferation of HNSCC cells via accumulation in S-phase through possible contribution of p53. The two PCT analogs can be widely used as research tools for cell cycle inhibition studies in proliferating cancer cells with specific mechanisms of action.

• Authors: Gunjan Guha, Wanli Lu, Shan Li, Xiaobo Liang, Molly F Kulesz-Martin, Taifo Mahmud, Arup Kumar Indra, Gitali Ganguli-Indra
• Journal: PloS one (PLoS One) Vol. 10 Issue 5 Pg. e0125322 ( 2015) ISSN: 1932-6203 [Electronic] United States
• PMID: 25938491 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Cyclin-Dependent Kinase Inhibitor p21
• Hydrocarbons, Fluorinated
• TM-025
• TM-026
• Tumor Suppressor Protein p53
• Pactamycin

Topics

• Apoptosis (drug effects)
• Autophagy (drug effects)
• Carcinoma, Squamous Cell (pathology)
• Cell Cycle Checkpoints (drug effects)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Cell Survival (drug effects)
• Cellular Senescence (drug effects)
• Cyclin-Dependent Kinase Inhibitor p21 (metabolism)
• Dose-Response Relationship, Drug
• Gene Silencing (drug effects)
• Head and Neck Neoplasms (pathology)
• Humans
• Hydrocarbons, Fluorinated (pharmacology)
• Models, Biological
• Pactamycin (analogs & derivatives, pharmacology)
• Protein Biosynthesis (drug effects)
• S Phase (drug effects)
• Squamous Cell Carcinoma of Head and Neck
• Tumor Suppressor Protein p53 (metabolism)
• Up-Regulation (drug effects)