Castration is a prerequisite for the inhibitory effect of metronomic chemotherapy on the growth of experimental castration-resistant prostate cancer

AbstractBackground: Low-dose metronomic chemotherapy (LDMC) is an alternative for treatment of patients with late-stage prostate cancer (PC) not susceptible to regular chemotherapy due to its severe side effects. The exact working mechanisms of LDMC have not been established, although anti-angiogenic effects have been identified. In PC, several studies show clinical effects from LDMC but the mode of action and the role of androgen signaling for its effect are not known. In this study, we used a xenograft model to evaluate the effect of LDMC on PC growth in relation to androgen deprivation.Material and methods: Subcutaneous human castration-resistant PC xenografts were treated with LDMC using cyclophosphamide (CPA). Treatment effect was compared to treatment with maximum tolerated dose (MTD) and also between intact and castrated mice. Microvessel density (MVD), and factors important for angiogenesis were analyzed with immunohistochemistry and real-time-PCR.Results: Tumors treated with LDMC were 50% smaller...