sq-23377 and Ovarian-Neoplasms

Resistance to cisplatin (CDDP)-based therapy is a major hurdle to the successful treatment of human ovarian cancer (OVCA), and the chemoresistant phenotype in OVCA cells is associated with Akt-attenuated p53-mediated apoptosis. Pro-apoptotic functions of p53 involve both transcription-dependent and -independent signaling pathways, and dysfunctional localization and/or inactivation of p53 contribute to the development of chemoresistance. PARC is a cytoplasmic protein regulating p53 subcellular localization and subsequent function. Little is known about the molecular mechanisms regulating PARC. Although PARC contains putative caspase-3 cleavage sites, and CDDP is known to induce the activation of caspases and calpains and induce proteasomal degradation of anti-apoptotic proteins, if and how PARC is regulated by CDDP in OVCA are unknown. Here, we present evidence that CDDP promotes calpain-mediated PARC down-regulation, mitochondrial and nuclear p53 accumulation, and apoptosis in chemosensitive but not resistant OVCA cells. Inhibition of Akt is required to sensitize chemoresistant cells to CDDP in a p53-dependent manner, an effect enhanced by PARC down-regulation. CDDP-induced PARC down-regulation is reversible by inhibition of calpain but not of caspases or the 26 S proteasome. Furthermore, in vitro experiments confirm the ability of calpain in mediating Ca(2+)-dependent PARC down-regulation. The role of Ca(2+) in PARC down-regulation was further confirmed as ionomycin-induced PARC down-regulation in both chemosensitive and chemoresistant ovarian cancer cells. The data presented here implicate the regulation of p53 subcellular localization and apoptosis by PARC as a contributing factor in CDDP resistance in OVCA cells and Ca(2+)/calpain in PARC post-translational processing and chemosensitivity.

Topics: Antineoplastic Agents; Apoptosis; Calcium; Calcium Ionophores; Calpain; Carrier Proteins; Caspase 3; Cell Line, Tumor; Cisplatin; Down-Regulation; Drug Resistance, Neoplasm; Enzyme Activation; Female; Gene Expression Regulation, Neoplastic; Humans; Ionomycin; Ovarian Neoplasms; Proteasome Endopeptidase Complex; Protein Processing, Post-Translational; Protein Transport; Transferases; Tumor Suppressor Protein p53

Most anti-cancer therapies induce apoptotic cell death, but a major barrier to long-term cancer treatments is the generation of apoptosis-resistant tumor cells. Tumor cells that become resistant to one therapy are usually cross-resistant to subsequent therapies, including those with different cellular/molecular targets, suggesting that resistant tumor cells acquire modifications of the general apoptotic pathway. Most solid tumors are characterized by infiltration of lymphocytes (tumor infiltrating lymphocytes, TIL), which may serve as a basis for new strategies to generate tumor specific lymphocytes. However, TIL frequently are unable to kill autologous tumor cells suggesting that they are anergic/tolerant. It is possible that the TIL are functional but the tumor cells are resistant to TIL-mediated apoptotic pathways. Previous findings revealed that resistant tumor cells can be sensitized with cytokines or subtoxic concentrations of chemotherapeutic drugs and restore killing by cytotoxic lymphocytes. In this study, we examined whether TIL can kill autologous and allogeneic tumor cells following sensitization with chemotherapeutic drugs. Renal and prostate cancer-derived TIL were cytotoxic to chemosensitized resistant tumor cells. Killing by TIL was found to be perforin-dependent and perforin-independent. These findings demonstrate that combination drug and immunotherapy may be able to overcome tumor cell resistance to killing by TIL. Further, in vivo sensitization of drug-resistant tumor cells by subtoxic doses of sensitizing chemotherapeutic drugs may result in tumor regression by the host immune system.

Topics: Adenocarcinoma; Antineoplastic Agents; Apoptosis; Carcinoma; Carcinoma, Renal Cell; Cisplatin; Combined Modality Therapy; Cytotoxicity, Immunologic; Drug Resistance, Neoplasm; Egtazic Acid; Fas Ligand Protein; fas Receptor; Female; Humans; Interleukin-2; Ionomycin; Kidney Neoplasms; Killer Cells, Lymphokine-Activated; Lymphocytes, Tumor-Infiltrating; Magnesium Chloride; Male; Membrane Glycoproteins; Ovarian Neoplasms; Perforin; Pore Forming Cytotoxic Proteins; Prostatic Neoplasms; Recombinant Proteins; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured