BACKGROUND:Piwi-interacting RNA (piRNA)-823 contributes to oncogenesis and tumor progression through multiple genes and pathways in several solid cancers and hematologic malignancies. Hence, the current study aimed to further explore the effects of piRNA-823 on cell growth and chemoresistance in multiple myeloma (MM) and the underlying molecular mechanism involved.
METHODS:Bone marrow plasma piRNA-823 expression was detected in 15 newly diagnosed MM (NDMM) patients, 15 relapse/refractory MM (RRMM) patients and 5 iron deficiency anemia patients as controls. The control mimic, piRNA-823 mimic, control inhibitor and piRNA-823 inhibitor were transfected; then, the control inhibitor and piRNA-823 inhibitor were transfected alone or in combination with transforming growth factor β1 (TGF-β1) into U266 or RPMI-8226 cells. piRNA-823, TGF-β1, cleaved caspase 3, Bcl-2, protein kinase (AKT), pAKT, extracellular signal regulated kinase (ERK), pERK, cell proliferation, apoptosis and chemoresistance were evaluated.
RESULTS:piRNA-823 expression was greater in NDMM patients and RRMM patients than in controls and was also greater in RRMM patients than in NDMM patients (all P < 0.01). In U266 and RPMI-8226 cells, piRNA-823 knockdown decreased proliferation and Bcl-2 expression but increased apoptosis, cleaved caspase-3 expression, and chemoresistance to bortezomib and lenalidomide (all P < 0.05). Moreover, piRNA-823 overexpression had opposite and weaker effects on these functions. piRNA-823 positively regulated the TGF-β1-mediated AKT/ERK pathway (all P < 0.05). Notably, TGF-β1 weakened the effects of piRNA-823 knockdown on the AKT/ERK pathway, cell proliferation, apoptosis, and apoptotic markers and, importantly, the chemoresistance to bortezomib and lenalidomide (all P < 0.05).
CONCLUSION:piRNA-823 promotes cell growth and chemoresistance by stimulating the TGF-β1-mediated AKT/ERK pathway in MM.