ABSTRACT
BACKGROUND: The anti-leukemic mechanism of homoharringtonine (HHT) differs from that of IM, and HHT is one of the most useful agents for use in patients with IM resistance or intolerance. The Bcl-6/p53 pathway has been shown to regulate the sensitivity of tumor cells to antitumor drugs. We tested whether HHT blocked the Bcl-6/p53 pathway in order to promote the apoptosis of IM-resistant cells in vitro and in vivo. RESULTS: Ph+ acute lymphoblastic leukemia (ALL) cells and IM-resistant chronic myeloid leukemia (CML) cells showed high expression of Bcl-6 protein. Bcl-6 mediated the upregulation of p53, and and Bcl-6 induced growth inhibition of IM-resistant cells as well as its apoptosis by targeting p53. In addition, Bcl-6 was downregulated moderately after HHT treatment in different cells. The Bcl-6 expression was significantly increased in patients with CML when compared with healthy subjects. Furthermore, the expression of Bcl-6 was higher in patients with CML-blastic phase (CML-BP) than in those with CML-chronic phase (CML-CP). METHODS: The inhibitory effect of drugs on cell growth was detected by Cell Counting Kit-8 (CCK-8), The apoptosis rate and the cell cycle were investigated by flow cytometry. The expression of Bcl-6, p53, Bcl-2, caspase9, and caspase3 proteins was assayed by western blot, Real- Time PCR (qPCR) detect Bcl-6 and p53 mRNA. CONCLUSIONS: HHT can suppress the growth and induce apoptosis of IM-resistant cells, the mechanism of which is associated with blocking of the Bcl-6/p53 pathway. Our results could offer a theoretical explanation for HHT use in patients with IM resistance or intolerance.
Subject(s)
Drug Resistance, Neoplasm/drug effects , Harringtonines/pharmacology , Imatinib Mesylate/pharmacology , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics , Proto-Oncogene Proteins c-bcl-6/genetics , Tumor Suppressor Protein p53/genetics , Adult , Aged , Antineoplastic Agents, Phytogenic/pharmacology , Apoptosis/drug effects , Apoptosis/genetics , Cell Cycle Checkpoints/drug effects , Cell Cycle Checkpoints/genetics , Cell Survival/drug effects , Cell Survival/genetics , Drug Resistance, Neoplasm/genetics , Female , Gene Expression Regulation, Leukemic/drug effects , Homoharringtonine , Humans , K562 Cells , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/metabolism , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology , Male , Middle Aged , Proto-Oncogene Proteins c-bcl-6/metabolism , RNA Interference , Signal Transduction/drug effects , Signal Transduction/genetics , Tumor Suppressor Protein p53/metabolism , Young AdultABSTRACT
BACKGROUND: Nowadays, despite great progress in cancer research, the detailed mechanisms of colorectal cancer (CRC) are still poorly understood. Circular RNAs (circRNAs), a new star of the non-coding RNA network, have been identified as critical regulators in various cancers, including CRC. METHODS AND RESULTS: In this study, by using unsupervised hierarchical clustering analysis, a novel dysregulated circRNA, hsa_circ_0000069, was found. The expression of hsa_circ_0000069 was measured in 30 paired CRC tissues and adjacent noncancerous tissues using quantitative polymerase chain reaction. A high expression of hsa_circ_0000069 was observed in CRC tissues and correlated with patients' age and tumor, node, metastasis (TNM) stage (P<0.05). Furthermore, by using specifically designed siRNAs in CRC cells, a functional analysis was performed which revealed that hsa_circ_0000069 knockdown could notably inhibit cell proliferation, migration, and invasion, and induce G0/G1 phase arrest of cell cycle in vitro. CONCLUSION: This study's findings are the first to demonstrate that hsa_circ_0000069, an important regulator in cancer progression, could be a promising target in the diagnosis and therapy in colorectal cancer.
