Recent Advances in the Studies of Molecular Mechanisms Regulating Multidrug Resistance in Cancer Cells

—Here we present new approaches to better understanding multidrug resistance (MDR) development in cancer cells, such as identification of components of a complex process of MDR evolution. Recent advances in the studies of MDR are discussed: 1) chemotherapy agents might be involved in the selection of cancer stem cells resulting in the elevated drug resistance and enhanced tumorigenicity; 2) cell–cell interactions have a great effect on the MDR emergence and evolution; 3) mechanotransduction is an important signaling mechanism in cell–cell interactions; 4) proteins of the ABC transporter family which are often involved in MDR might be transferred between cells via microvesicles (epigenetic MDR regulation); 5) proteins providing cell-to-cell transfer of functional P-glycoprotein (MDR1 protein) via microvesicles have been investigated; 6) P-glycoprotein may serve to regulate apoptosis, as well as transcription and translation of target genes/proteins. Although proving once again that MDR is a complex multi-faceted process, these data open new approaches to overcoming it.