Treatment with cucurbitacin B alone and in combination with gefitinib induces cell cycle inhibition and apoptosis via EGFR and JAK/STAT pathway in human colorectal cancer cell lines

• Published in: Human & experimental toxicology 2016-05, Vol.35 (5), p.526-543
• Main Authors: Yar Saglam, AS, Alp, E, Elmazoglu, Z, Menevse, S
• Format: Article
• Language: English
• Subjects: Adenosine; Anticancer properties; Antineoplastic Combined Chemotherapy Protocols - administration & dosage; Antineoplastic Combined Chemotherapy Protocols - pharmacology; Antitumor activity; Apoptosis; Apoptosis - drug effects; Apoptosis - genetics; Assaying; Bcl-2 protein; Binding; Biotechnology; Blotting, Western; Caspase; Caspase-3; Cell cycle; Cell Cycle - drug effects; Cell Cycle - genetics; Cell proliferation; Cell Proliferation - drug effects; Cell Survival - drug effects; Chronic lymphocytic leukemia; Colorectal cancer; Colorectal carcinoma; Cyclin D1; Cyclin-dependent kinase inhibitor p27; Cytotoxicity; Death; Deoxyribonucleic acid; DNA; DNA biosynthesis; DNA fragmentation; Epidermal growth factor; Epidermal growth factor receptors; Fluorescence; Fragmentation; Gene expression; HCT116 Cells; Homology; HT29 Cells; Humans; In vitro methods and tests; Inhibition; Inhibitor drugs; Inhibitors; Janus Kinases - genetics; Janus Kinases - metabolism; Kinases; Lymphocytes B; Lymphoma; Microscopy; Microscopy, Fluorescence; Mortality; Phosphates; Phosphorylation; Polymerase chain reaction; Proteins; Quinazolines - administration & dosage; Quinazolines - pharmacology; Real time; Real-Time Polymerase Chain Reaction; Receptor, Epidermal Growth Factor - genetics; Receptor, Epidermal Growth Factor - metabolism; Signal transduction; Signal Transduction - drug effects; STAT Transcription Factors - genetics; STAT Transcription Factors - metabolism; Toxicity; Transcription; Triterpenes - administration & dosage; Triterpenes - pharmacology; Viability
• ISSN: 0960-3271; 1477-0903
• DOI: 10.1177/0960327115595686

The epidermal growth factor receptor (EGFR) associated with signaling pathways, such as Janus kinase (JAK)/signal transducer and activator of transcription (STAT), plays an important role in colorectal cancers (CRCs). Gefitinib (Gef) is an orally active inhibitor targeting the adenosine tri phosphate-binding domain of EGFR, and cucurbitacin B (CuB) is a selective inhibitor of JAK/STAT signaling with potent antitumor activity via suppression of STAT3 phosphorylation, but the underlying mechanism is not clear. We aimed to investigate the apoptotic and antiproliferative effects of CuB as a single agent and in combination with Gef on both HT-29 and HCT-116 cell lines. Cell proliferation, cell cycle distribution, and apoptosis were evaluated using viability assay, fluorescent microscopy, cytotoxicity assay, proliferation, DNA fragmentation, and cleaved caspase 3 levels. Real-time polymerase chain reaction and Western blot analyses were performed to determine the expression of relevant genes and proteins including antiapoptotic, proapoptotic, and cell cycle regulation. EGFR, phosphorylated EGFR (pEGFR), STAT3, and pSTAT3 proteins were evalutaed with Western blot analysis. Our results showed that, compared to CuB alone, CuB plus Gef treatment caused a significant growth and cell cycle inhibition and induced apoptosis in both cell lines. Also CuB plus Gef treatment decreased DNA synthesis rate more effectively than CuB alone. Treatment with CuB alone and in combination with Gef decreased the expression levels of B-Cell CLL/Lymphoma 2 (Bcl-2), BCL2-like 1 (BCL2L1), cyclin D1, pSTAT3, and pEGFR and increased the expression levels of Bcl-2-like protein 4, Bcl-2 homologous antagonist/killer, Bcl-2-associated death promoter, Bcl-2-like protein 11, and p27kip1 levels. Our results suggest that treatment with CuB alone and more likely in combination with Gef may be a considerable alternative therapeutic approach for CRC, at least in vitro.