homocamptothecin and Adenocarcinoma

Arl4c is overexpressed in several cancer tissues and is involved in cancer development. Nevertheless, the exact mechanism that regulates Arl4c expression in lung cancer has not been fully elucidated. The aim of this study was to investigate the regulatory mechanism of Arl4c and to explore potential chemotherapeutic drugs targeting Arl4c.. Immunohistochemistry was used to examine Arl4c expression levels in human lung adenocarcinoma cancer specimens. Protein expression was detected by western blot. Overexpression of Arl4c-Flag protein was used to detect the ubiquitination of Arl4c. A short interfering RNA against Arl4c was used for gene silencing.. Arl4c was overexpressed in lung cancer tissues, and knockdown of Arl4c expression by siRNA decreased lung cancer A549 and 95-D cell proliferation. In addition, Arl4c expression was downregulated via inhibition of the AKT pathway in A549 and 95-D cells, whereas exposure to benzo (a) pyrene (a carcinogen in smoke) increased Arl4c expression in 16HBE cells via AKT activation. Finally, we found that chemotherapy drug hydroxycamptothecin (HCPT) could decrease Arl4c expression levels by inhibiting the activation of the AKT pathway in A549 and 95-D cells. Moreover, accumulation of ubiquitinated Arl4c protein was increased by HCPT and LY294002 (an AKT inhibitor) treatment whereas the proteasome inhibitor MG-132 attenuated the inhibitory effect of HCPT and LY294002 on Arl4c expression.. Here, we highlighted the AKT pathway as an important regulatory pathway for Arl4c expression in lung cancer cells and identified HCPT as a promising drug for lung adenocarcinoma treatment that functioned by targeting Arl4c expression.

Topics: A549 Cells; Adenocarcinoma; Adenocarcinoma of Lung; ADP-Ribosylation Factors; Blotting, Western; Camptothecin; Cell Line, Tumor; Chromones; Gene Expression Regulation, Neoplastic; Gene Knockdown Techniques; Humans; Leupeptins; Lung Neoplasms; Morpholines; Proto-Oncogene Proteins c-akt; Signal Transduction; Smoking

The multidrug-resistance (MDR) status of a novel camptothecin analogue, homocamptothecin (hCPT), was investigated in human colon adenocarcinoma HT29 cells, myelogenous leukemia K562 cells and breast carcinoma MCF7 cells. The cytotoxicity of hCPT was not sensitive to the MDR status in K562 cell lines. However, its cytotoxicity was altered by MRP1, but not Pgp, in naturally MRP1-expressing HT29 cells, and etoposide- and doxorubicin-resistant MCF7/VP and MCF7/DOX cells, respectively. These cells were sensitized to hCPT in presence of MK571, probenecid but not verapamil. These results led to consider hCPT as a substrate for MRP1 and a potential modulator of MRP1 activity. The relationship between the cytotoxic effect of anthracyclines and their nuclear localization had been previously demonstrated. We show that MRPI mediated the daunorubicin (DNR) efflux in MCF7/VP and MCF7/DOX cells. The combination of sub-toxic doses of hCPT with DNR resulted in the potentiation of DNR activity, well-correlated with an increase in its nuclear accumulation in MCF7/VP cells. Simultaneous pattern was shown to provide higher cytotoxic response than sequential one. In agreement, hCPT increased also the DNR nuclear accumulation in low MRP1-expressing MCF7/DOX cells. However, the enhancement of cytotoxicity in the DNR-hCPT combination was poorly correlated with the nuclear concentration of DNR in MCF7/DOX cells. In addition to the increase in DNR accumulation, the potentiation of DNR activity by hCPT in MCF7/DOX cells implied a synergistic mechanism between both drugs. These data suggest that the present topoisomerase I/II inhibitors combination may be of clinical interest to overcome MDR phenotype in DNR-treated breast cancer patients.

Topics: Adenocarcinoma; Antibiotics, Antineoplastic; Antineoplastic Combined Chemotherapy Protocols; Breast Neoplasms; Camptothecin; Carcinoma; Colonic Neoplasms; Daunorubicin; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Drug Synergism; Female; Flow Cytometry; Gene Expression Regulation, Neoplastic; Humans; In Vitro Techniques; Leukemia, Myeloid; Microbial Sensitivity Tests; Multidrug Resistance-Associated Proteins; Polymerase Chain Reaction; RNA, Neoplasm; Treatment Outcome; Tumor Cells, Cultured