IL-6 Regulates the Chemosensitivity of Drug-Resistant Multiple Myeloma Cell Lines to Bortezomib through STAT3/Notch Signaling Pathway

Abstract

To investigate the effect of interleukin-6 (IL-6) on the chemosensitivity of drug-resistant multiple myeloma (MM) cell lines to bortezomib (BTZ) and its mechanism. Peripheral blood samples were collected from patients with BTZ-resistant MM before and after treatment. Human MM cell lines KM3 and KM3/BTZ were cultured in vitro. ELISA was used to detect the content of IL-6 in peripheral blood of MM patients, KM3 and KM3/BTZ cells. CCK-8 assay was used to detect the drug sensitivity of KM3 and KM3 / BTZ cells to BTZ. KM3 / BTZ cells were divided into KM3/BTZ control group (normal culture for 48 h), IL-6 neutralizing antibody Anti-IL-6 group (500 ng/ml Anti-IL-6 treated for 48 h), BTZ group (300 ng/ml BTZ treated for 48 h), BTZ + Anti-IL-6 group (300 ng/ml BTZ and 500 ng/ml Anti-IL-6 treated for 48 h). The proliferation activity of KM3 / BTZ cells was detected by CCK-8 assay. The cell cycle distribution of KM3/BTZ cells was detected by flow cytometry. The apoptosis of KM3/BTZ cells was detected by Annexin V-FITC/PI double staining. The mRNA expression levels of IL-6, Notch1, signal transducer and activator of transcription 3 (STAT3) in KM3/BTZ cells were detected by real-time fluorescent quantitative PCR (qRT-PCR), and the protein expression levels of IL-6, Notch1, STAT3 in KM3/BTZ cells were detected by Western blot. The level of IL-6 in peripheral blood of patients with BTZ-resistant MM after treatment was significantly higher than that before treatment (P<0.05). The level of IL-6 in KM3/BTZ cells was significantly higher than that in KM3 cells (P<0.05). The sensitivity of KM3/BTZ cells to BTZ was significantly lower than that of KM3 cells (P<0.05), and the resistance index (RI) was 19.62. Anti-IL-6 and BTZ could inhibit the proliferation of KM3 / BTZ cells, block cell cycle, and induce apoptosis (P<0.05). Compared with single drug treatment, the combined effect of Anti-IL-6 and BTZ was more obvious on KM3/BTZ cells (P<0.05), and significantly down regulated the mRNA and protein expression of IL-6, Notch1 and STAT3 in KM3/BTZ cells (P<0.05). Antagonizing IL-6 can increase the chemosensitivity of MM cells to BTZ, and IL-6 may reduce the sensitivity of MM cells to BTZ through STAT3/Notch signaling pathway.