KCNJ15 deficiency promotes drug resistance via affecting the function of lysosomes

The altered lysosomal function can induce drug redistribution which leads to drug resistance and poor prognosis for cancer patients.V-ATPase,an ATP-driven proton pump positioned at lysosomal surfaces,is responsible for maintaining the stability of lysosome.Herein,we reported that the potassium voltage-gated channel subfamily J member 15(KCNJ15)protein,which may bind to V-ATPase,can regulate the function of lysosome.The deficiency of KCNJ15 protein in breast cancer cells led to drug aggregation as well as reduction of drug efficacy.The application of the V-ATPase inhibitor could inhibit the binding between KCNJ15 and V-ATPase,contributing to the amelioration of drug resistance.Clinical data analysis revealed that KCNJ15 deficiency was associated with higher histological grading,advanced stages,more metastases of lymph nodes,and shorter disease free survival of patients with breast cancer.KCNJ15 expression level is positively correlated with a high response rate after receiving neoadjuvant chemotherapy.Moreover,we revealed that the small molecule drug CMA/BAF can reverse drug resistance by disrupting the interaction between KCNJ15 and lysosomes.In conclusion,KCNJ15 could be identified as an underlying indicator for drug resistance and survival of breast cancer,which might guide the choice of therapeutic strategies.

FSIP1 enhances the therapeutic sensitivity to CDK4/6 inhibitors in triple-negative breast cancer patients by activating the Nanog pathway

CDK4/6 inhibitors are routinely recommended agents for the treatment of advanced HR+HER2-breast cancer.However,their therapeutic effectiveness in triple-negative breast cancer(TNBC)remains controversial.Here,we observed that the expression level of fibrous sheath interacting protein 1(FSIP1)could predict the treatment response of TNBC to CDK4/6 inhibitors.High FSIP1 expression level was related to a poor prognosis in TNBC,which was associated with the ability of FSIP1 to promote tumor cell proliferation.FSIP1 downregulation led to slowed tumor growth and reduced lung metastasis in TNBC.FSIP1knockout caused cell cycle arrest at the G0/G1 phase and reduced treatment sensitivity to CDK4/6 inhibitors by inactivating the Nanog/CCND1/CDK4/6 pathway.FSIP1 could form a complex with Nanog,protecting it from ubiquitination and degradation,which may facilitate the rapid cell cycle transition from G0/G1 to S phase and exhibit enhanced sensitivity to CDK4/6 inhibitors.Our findings suggest that TNBC patients with high FSIP1 expression levels may be suitable candidates for CDK4/6 inhibitor treatment.