The underlying molecular mechanisms of CT resistance has not been fully clarified. Genetic and non-genetic alterations have been suspected to be involved in the development of drug resistance in previous studies.12,13 Although this resistance appears to be multifactorial; defects in tubulin and microtubule-associated proteins (MAPs), dysregulated cell cycle and apoptotic signaling pathways are among the factors thought to be responsible for taxane resistance.14 Researchers have demonstrated the relationship between taxane resistance and the overexpression of MAPs, tau protein, STHMN1 and OPN with in vitro and in vivo studies.4,6 We investigated whether STHMN1 and OPN expressions could be predictive markers for cancer metastasis and resistance to TBR in mCRPC. It has been reported that OPN plays an important role in the progression of several cancers through the regulation of vascular endothelial growth factor (VEGF) release in the PI3K signaling pathway and the effectiveness of various physiological processes.4,15