Klotho-beta attenuates Rab8a-mediated exosome regulation and promotes prostate cancer progression

Tumor-secreted exosomes have a wide range of effects on the growth, metastasis, and drug resistance of cancer cells. However, whether and how the molecular mechanisms that regulate the secretion of exosomes could affect tumor progression remains poorly understood. Klotho beta (KLB) has been reported dysregulated in prostate cancer, but its function remains unknown. Herein, we first determined that KLB was upregulated in prostate cancer and its expression level was positively correlated with prostate cancer malignant phenotype both in vitro and in vivo. Intriguingly, KLB overexpression could impair the release of exosomes and cause the intracellular accumulation of multivesicular bodies (MVBs) in prostate cancer cells. Mechanistically, KLB attenuated exosomes secretion through a Rab8a-dependent pathway. Rab8a was downregulated in KLB overexpressing cells whereas overexpression of Rab8a could rescue the impaired release of exosomes and attenuate the KLB-induced malignant phenotype of prostate cancer both in vitro and in vivo. Taken together, this study has unveiled the tumor-promoting role of KLB mediated by its regulation on exosomes secretion through a Rab8a-dependent mechanism. These findings could be exploited to develop novel theranostic targets for prostate cancer.