Recent studies have reported that TUBB3 overexpression is involved in docetaxel (DTX) resistance in prostate cancer (PCa). The aim of this study was to clarify the role of TUBB3 in DTX and cabazitaxel (CBZ) resistance, and cross-resistance between DTX and CBZ in PCa. We analyzed the effect of TUBB3 knockdown on DTX and CBZ resistance and examined the interaction between TUBB3 and PTEN. We also investigated the role of phosphoinositide 3-kinases (PI3K) inhibitor (LY294002) in DTX and CBZ resistance. TUBB3 expression was upregulated in DTX-resistant and CBZ-resistant cells. TUBB3 knockdown re-sensitized DTX-resistant cells to DTX and CBZ-resistant cells to CBZ. Additionally, TUBB3 knockdown re-sensitized DTX-resistant cell lines to CBZ, indicating that TUBB3 mediates cross-resistance between DTX and CBZ. Knockdown of TUBB3 enhanced PTEN expression, and PTEN knockout enhanced TUBB3 expression. LY294002 suppressed TUBB3 expression in DTX-resistant and CBZ-resistant cell lines. LY294002 re-sensitized DTX-resistant cell lines to DTX and CBZ-resistant cell lines to CBZ. These results suggest that TUBB3 is involved in DTX resistance and CBZ resistance. A combination of LY294002/DTX and that of LY294002/CBZ could be potential strategies for PCa treatment.

Kinesin family member C1 (KIFC1) is a minus end-directed motor protein that plays an essential role in centrosome clustering. Previously, we reported that KIFC1 is involved in cancer progression in prostate cancer (PCa). We designed this study to assess the involvement of KIFC1 in docetaxel (DTX) resistance in PCa and examined the effect of KIFC1 on DTX resistance. We also analyzed the possible role of a KIFC1 inhibitor (CW069) in PCa. We used DTX-resistant PCa cell lines in DU145 and C4-2 cells to analyze the effect of KIFC1 on DTX resistance in PCa. Western blotting showed that KIFC1 expression was higher in the DTX-resistant cell lines than in the parental cell lines. Downregulation of KIFC1 re-sensitized the DTX-resistant cell lines to DTX treatment. CW069 treatment suppressed cell viability in both parental and DTX-resistant cell lines. DTX alone had little effect on cell viability in the DTX-resistant cells. However, the combination of DTX and CW069 significantly reduced cell viability in the DTX-resistant cells, indicating that CW069 re-sensitized the DTX-resistant cell lines to DTX treatment. These results suggest that a combination of CW069 and DTX could be a potential strategy to overcome DTX resistance.

Cancer Drug Resistance is an open access journal, focusing on pharmacological aspects of drug resistance and its reversal, molecular mechanisms of drug resistance and drug classes, etc. Both clinical and experimental aspects of drug resistance in cancer are included.

Objective: Esophageal cancer is one of the deadliest cancers in the world, and the main subtype is esophageal squamous cell carcinoma (ESCC), which comprises 90% of cases. Expression of tryptophan 2,3-dioxygenase (TDO2), an enzyme involved in tryptophan catabolism, has been linked with tumor survival and poor prognosis of brain and breast cancer. However, no studies have investigated the potential role of TDO2 in esophageal cancer. Here we explored the expression and biological significance of TDO2 in ESCC. Methods: TDO2 protein expression was evaluated in 90 ESCC tissue samples by immunohistochemistry. TDO2 function in ESCC cell lines and spheroid colony formation were evaluated by RNA interference (RNAi). Results: TDO2 overexpression was associated with tumor stage, recurrence status, and the CD44 cancer stem cell marker in ESCC. TDO2 overexpression was correlated with poor outcome of ESCC patients. Inhibition of TDO2 expression by RNAi in TE-10 and TE-11 cell lines reduced both the number and the size of spheroid colonies as well as cell proliferation. Knockdown of TDO2 expression also induced inactivation of the epidermal growth factor receptor signaling pathway. Conclusion: Our results imply that TDO2 could play an important role in the progression of ESCC. Furthermore, TDO2 may be a potential therapeutic target in ESCC.

Background/Aim: Targeted receptor tyrosine kinase inhibitor (TKI) is a standard treatment in advanced renal cell carcinoma (RCC). However, the role of PTEN in TKI resistance remains poorly understood. We aimed to determine the functional role of PTEN knockout and analyse the predictive significance of PTEN expression for TKI treatment in RCC. Materials and Methods: We developed PTEN knockout cells in RCC cell lines using the CRISPR-Cas9 system and analysed the effect of PTEN knockout on spheroid formation and resistance to sunitinib and sorafenib. Results: PTEN knockout promoted spheroid formation and decreased sunitinib/sorafenib sensitivity in RCC cell lines. PTEN immunohistochemistry in 74 metastatic RCCs treated with sunitinib and sorafenib revealed negative PTEN expression in 23% of samples. Kaplan–Meier analysis showed a significant association of negative PTEN expression with poor progression-free survival in metastatic RCC treated with sunitinib and sorafenib (p=0.024) or sunitinib alone (p=0.009). Conclusion: PTEN may be a biomarker and therapeutic target in patients with metastatic RCC.

Introduction: BUB1 mitotic checkpoint serine/threonine kinase B encoded by BUB1B gene is a member of the spindle assembly checkpoint family. Several reports have demonstrated that overexpression of BUB1B is associated with cancer progression and prognosis. Objective: This study aims to clarify the expression and function of BUB1B in renal cell carcinoma (RCC). Methods: The expression of BUB1B was determined using immunohistochemistry and bioinformatics analysis in RCC. The effects of BUB1B knockdown on cell growth and invasion were evaluated. We analyzed the interaction between BUB1B, cancer stem cell markers, p53, and PD-L1 in RCC. Results: In 121 cases of RCC, immunohistochemistry showed that 30 (25%) of the RCC cases were positive for BUB1B. High BUB1B expression was significantly correlated with high nuclear grade, T stage, and M stage. A Kaplan-Meier analysis showed that the high expression of BUB1B was associated with poor overall survival after nephrectomy. High BUB1B expression was associated with CD44, p53, and PD-L1 in RCC. Knockdown of BUB1B suppressed cell growth and invasion in RCC cell lines. Knockdown of BUB1B also suppressed the expression of CD44 and increased the expression of phospho-p53 (Ser15). In silico analysis showed that BUB1B was associated with inflamed CD8+, exhausted T-cell signature, IFN-γ signature, and the response to nivolumab. Conclusion: These results suggest that BUB1B plays an oncogenic role and may be a promising predictive biomarker for survival in RCC.