bafilomycin-a and Uterine-Cervical-Neoplasms

Increasing resistance to cisplatin as well as the severity of the adverse effects limit the use of this drug, particularly at high doses. Evidence has implicated the importance of autophagy in cancer resistance as well as the fact that various chemotherapy agents induce autophagy in cancer cells. We therefore aimed to first assess the role of autophagy in cisplatin treatment and second to assess whether a nontoxic concentration of cisplatin, together with autophagy inhibition, is able to maintain its cancer-specific cytotoxic action.. Three human cervical cell lines were used: a noncancerous ectocervical epithelial cell line (Ect1/E6E7) and 2 cancerous cervical cell lines (HeLa and CaSki). Autophagy was monitored through the presence of the classical protein markers LC-3 II and p62 under basal and treatment conditions, and inhibited using bafilomycin and autophagy protein 5 (ATG5) siRNA under treatment conditions. Cell death was analyzed through examination of the apoptotic markers PARP and caspase-3 through Western blotting, as well as the Caspase-Glo assay to confirm caspase-3/7 activity. Cervical biopsies were analyzed for the presence of LC-3 using Western blotting and immunofluorescence to determine if a correlation between autophagic levels and the progression of the disease exists.. Cervical cancer cells exhibit increased basal autophagic levels in comparison to the noncancerous counterparts. Cisplatin treatment enhanced autophagic activity in all 3 cell lines. Inhibition of this autophagic response together with cisplatin treatment leads to significant increases in cancer cell death. Expression profiles of LC-3 in normal, premalignant (low-grade and high-grade squamous intraepithelial lesion), and cancerous cervical tissue revealed that autophagy is significantly up-regulated in HSILs and carcinoma cervical tissue, which emphasized the role of autophagy in the progression of the disease.. The inhibition of autophagy improves the cytotoxicity of a nontoxic concentration of cisplatin and provides a promising new avenue for the future treatment of cervical cancer.

Topics: Antineoplastic Agents; Autophagy; Autophagy-Related Protein 5; Carcinoma; Cisplatin; Drug Resistance, Neoplasm; Enzyme Inhibitors; Female; HeLa Cells; Humans; Macrolides; Microtubule-Associated Proteins; RNA-Binding Proteins; RNA, Small Interfering; Squamous Intraepithelial Lesions of the Cervix; Uterine Cervical Neoplasms

GS-9191, a bis-amidate prodrug of the nucleotide analog 9-(2-phosphonylmethoxyethyl)-N6-cyclopropyl-2,6-diaminopurine (cPrPMEDAP), was designed as a topical agent for the treatment of papillomavirus-associated proliferative disorders, such as genital warts. In this study, we investigated the mechanism of conversion of GS-9191 to cPrPMEDAP. We observed that GS-9191 is hydrolyzed in the presence of the lysosomal carboxypeptidase cathepsin A (CatA) in vitro and is less efficiently metabolized in CatA-deficient fibroblasts than in control cells. In addition, knockdown of CatA by small interfering RNA (siRNA) reduced the intracellular accumulation of GS-9191 metabolites. However, intracellular CatA levels did not correlate with the susceptibility of tested cell lines to GS-9191, indicating that the CatA step is unlikely to be rate limiting for the activation of GS-9191. Further analysis showed that upon the hydrolysis of the carboxylester bond in one of the GS-9191 amidate moieties, the unmasked carboxyl group displaces L-phenylalanine 2-methylpropyl ester from the other amidate moiety. The cPrPMEDAP-L-phenylalanine conjugate (cPrPMEDAP-Phe) formed is not metabolized by Hint1 (histidine triad nucleotide binding protein 1) phosphoramidase but undergoes spontaneous degradation to cPrPMEDAP in acidic pH that can be significantly enhanced by the addition of SiHa cell extract. Pretreatment of SiHa cells with bafilomycin A or chloroquine resulted in an 8-fold increase in the intracellular concentration of cPrPMEDAP-Phe metabolite and the accumulation of GS-9191 metabolites in the lysosomal/endosomal fraction. Together, these observations indicate that the conversion of GS-9191 to cPrPMEDAP occurs in lysosomes via CatA-mediated ester cleavage, followed by the release of cPrPMEDAP, most likely through the combination of enzyme-driven and spontaneous pH-driven hydrolysis of a cPrPMEDAP-Phe intermediate.

Topics: Antiviral Agents; Cathepsin A; Cell Line, Tumor; Chloroquine; Female; HeLa Cells; Humans; Hydrogen-Ion Concentration; Immunoblotting; Lysosomes; Macrolides; Papillomaviridae; Phenylalanine; Uterine Cervical Neoplasms

We studied the in vitro mechanism of etoposide-induced cell death in cervical cancer cells. Etoposide is cytotoxic to these cells, causing cell death by both apoptosis and autophagy, which has recently been described as a possible mechanism for nonapoptotic cell death. Electron microscopy revealed that autophagosomes/autolysosomes exhibited an autophagic appearance in the presence of etoposide. When autophagy was blocked by inhibitors of autophagy, including 3-methyladenine, both the expression of beclin 1 protein and the antitumor effect of etoposide were suppressed. Benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, a pan-caspase inhibitor, reduced etoposide-induced cytotoxicity in CaSki cells. Hence, autophagy and apoptosis likely occur concurrently in etoposide-treated cervical cancer cells.

Topics: Adenine; Amino Acid Chloromethyl Ketones; Antineoplastic Agents, Phytogenic; Apoptosis; Apoptosis Regulatory Proteins; Autophagy; Beclin-1; Caspase Inhibitors; Caspases; Cell Line, Tumor; Etoposide; Female; Humans; Macrolides; Membrane Proteins; Uterine Cervical Neoplasms