title: P276-00, a novel cyclin-dependent inhibitor induces G1-G2 arrest, shows antitumor activity on cisplatin-resistant cells and significant in vivo efficacy in tumor models.
abstract: P276-00, a flavone that inhibits cyclin-dependent kinases, has been identified by us recently as a novel antineoplastic agent. In this study, we have selected a panel of human tumor cell lines and xenografts to allow determination of selectivity and efficacy of P276-00. When tested against a panel of 16 cisplatin-sensitive and cisplatin-resistant cell lines, the antiproliferative potential of P276-00 was found to be approximately 30-fold higher than cisplatin. Studies to show tumor sensitivity using clonogenic assay in 22 human xenografts indicated that P276-00 was approximately 26-fold more potent than cisplatin, and further, it was also found to be active against cisplatin-resistant tumors of central nervous system, melanoma, prostate, and renal cancers. Further, we studied the effects of P276-00 on cell cycle progression by flow cytometry using asynchronous and synchronous population of tumor and normal cells. Asynchronous population of human prostate carcinoma (PC-3) and human promyelocytic leukemia (HL-60) cells when exposed to P276-00 showed arrest of slow-growing PC-3 cells in G(2)-M with no significant apoptosis observed up to 72 h. Unlike PC-3, significant apoptosis was seen in fast-growing HL-60 cells at 6 h. However, synchronized human non-small cell lung carcinoma (H-460) and human normal lung fibroblast (WI-38) cells showed arrest of cells in G(1). H-460 cells undergo apoptosis, which increases with longer exposure to the compound and also after exposure to P276-00 for 48 h followed by recovery. In contrast, the normal cells (WI-38) remain arrested in G(1) with no significant apoptosis up to 72 h of exposure and also after 48 h of P276-00 treatment followed by recovery, confirming our previous results that P276-00 was less effective against normal cells compared with cancer cells. After promising in vitro results, P276-00 was checked for in vivo efficacy in murine tumor and human xenograft models. Growth inhibition of murine colon cancer (CA-51) was significant when P276-00 was administered i.p. at 50 mg/kg daily for 20 treatments. However, in murine lung carcinoma model (Lewis lung), an increased dose of 60 mg/kg (30 mg/kg twice daily) administered every alternate day i.p. for seven treatments showed significant inhibition in the growth. Further studies were undertaken to establish the efficacy profile of P276-00 in human tumor xenograft models. In the two xenograft models studied, P276-00 showed potent in vivo antitumor potential. Compound P276-00 at a dose of 35 mg/kg administered daily via the i.p. route for 10 days showed significant (P < 0.05) inhibition in the growth of human colon carcinoma HCT-116 xenograft. Furthermore, P276-00 at a dose of 50 mg/kg once daily and 30 mg/kg twice daily administered via i.p. route for 20 treatments significantly (P < 0.05) inhibited growth of human non-small cell lung carcinoma H-460 xenograft. Thus, the in vitro cellular potency, together with in vivo antitumor activity, confirms the potential of P276-00, a cyclin-dependent kinase inhibitor as an anticancer molecule.
authors.affiliation: Department of Pharmacology, Nicholas Piramal Research Center, Nicholas Piramal India Ltd., 1-Nirlon Complex, Goregaon (East), Mumbai 400 063, India. kjoshi@nicholaspiramal.co.in
authors.forename: Kalpana S
authors.initials: KS
authors.lastname: Joshi
authors.forename: Maggie J
authors.initials: MJ
authors.lastname: Rathos
authors.forename: Pravin
authors.initials: P
authors.lastname: Mahajan
authors.forename: Vilas
authors.initials: V
authors.lastname: Wagh
authors.forename: Satyendra
authors.initials: S
authors.lastname: Shenoy
authors.forename: Dimple
authors.initials: D
authors.lastname: Bhatia
authors.forename: Shailaja
authors.initials: S
authors.lastname: Chile
authors.forename: Meenakshi
authors.initials: M
authors.lastname: Sivakumar
authors.forename: Armin
authors.initials: A
authors.lastname: Maier
authors.forename: Heinz-Herbert
authors.initials: HH
authors.lastname: Fiebig
authors.forename: Somesh
authors.initials: S
authors.lastname: Sharma
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002945:Cisplatin / Q000627:therapeutic use; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004195:Disease Models, Animal; D019008:Drug Resistance, Neoplasm; D047309:Flavones / Q000494:pharmacology*; D005434:Flow Cytometry; D016195:G2 Phase / Q000187:drug effects*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D009374:Neoplasms, Experimental / Q000188:drug therapy* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D047309:Flavones; C520467:P276-00; D018844:Cyclin-Dependent Kinases; D002945:Cisplatin