Novel Pactamycin Analogs Induce p53 Dependent Cell-Cycle Arrest at S-Phase in Human Head and Neck Squamous Cell Carcinoma (HNSCC) Cells.
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.
Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America.
Gunjan
G
Guha
Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America; Molecular and Cell Biology Program, Oregon State University, Corvallis, Oregon, United States of America.
Wanli
W
Lu
Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America.
Shan
S
Li
Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America.
Xiaobo
X
Liang
Department of Dermatology, Oregon Health and Science University, Portland, Oregon, United States of America.
Molly F
MF
Kulesz-Martin
Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America; Molecular and Cell Biology Program, Oregon State University, Corvallis, Oregon, United States of America.
Taifo
T
Mahmud
Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America; Molecular and Cell Biology Program, Oregon State University, Corvallis, Oregon, United States of America; Department of Dermatology, Oregon Health and Science University, Portland, Oregon, United States of America; Environmental Health Science Center, Oregon State University, Corvallis, Oregon, United States of America.
Arup Kumar
AK
Indra
Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America; Molecular and Cell Biology Program, Oregon State University, Corvallis, Oregon, United States of America.
Gitali
G
Ganguli-Indra
D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D059447:Cell Cycle Checkpoints / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D016922:Cellular Senescence / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D020868:Gene Silencing / Q000187:drug effects; D006258:Head and Neck Neoplasms / Q000473:pathology*; D006801:Humans; D006845:Hydrocarbons, Fluorinated / Q000494:pharmacology*; D008954:Models, Biological; D010142:Pactamycin / Q000031:analogs & derivatives* / Q000494:pharmacology; D014176:Protein Biosynthesis / Q000187:drug effects; D016196:S Phase / Q000187:drug effects*; D000077195:Squamous Cell Carcinoma of Head and Neck; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects
D050759:Cyclin-Dependent Kinase Inhibitor p21; D006845:Hydrocarbons, Fluorinated; C583546:TM-025; C583545:TM-026; D016159:Tumor Suppressor Protein p53; D010142:Pactamycin