Tumor Cell-Derived Microvesicles Induced Not Epithelial-Mesenchymal Transition but Apoptosis in Human Proximal Tubular (HK-2) Cells: Implications for Renal Impairment in Multiple Myeloma

Renal impairment (RI) is one of the hallmarks of multiple myeloma (MM) and carries a poor prognosis. Microvesicles (MVs) are membrane vesicles and play an important role in disease progression. Here, we investigated the role of MVs derived from MM cells (MM-MVs) in RI of MM. We found that MM-MVs significantly inhibited viability and induced apoptosis, but not epithelial-mesenchymal transition in human kidney-2 (HK-2), a human renal tubular epithelial cell line. The protein levels of cleaved caspase-3, 8, and 9, and E-cadherin, were increased, but vementin levels were decreased in the HK-2 cells treated with MM-MVs. Through a comparative sequencing and analysis of RNA content between the MVs from RPMI8226 MM cells (RPMI8226-MVs) and K562 leukemia cells, RPMI8226-MVs were enriched with more renal-pathogenic miRNAs, in which the selective miRNAs may participate in the up-regulation of the levels of cleaved caspase-3. Furthermore, the levels of CD138+ circulating MVs (cirMVs) in the peripheral blood were positively correlated with the severity of RI in newly-diagnosed MM. Our study supports MM-MVs representing a previously undescribed factor and playing a potential role in the development of RI of MM patients, and sheds light on the potential application of CD138+ cirMV counts in precise diagnosis of RI in MM and exploring MM-MVs as a therapeutic target.