Antiproliferative activity of marine-derived oligopeptides combined with androgen receptor inhibition in preclinical prostate cancer models.

Abstract

e15186 Background: Recent cancer statistics reveal a sustained increase in the incidence of prostate cancer (PC) of 3% per year. More than half of this increase is attributable to advanced disease. Advanced PC remains largely incurable, owing to inevitable progression. Escalation of therapy can restore tumor control, but significant sequelae may result. Anticancer peptides of marine origin appear intrinsically target specific and may constitute a novel approach to improve the therapeutic sensitivity of resistant cancers. Recently published in vitro work showed that a marine soluble protein hydrolysate (SPH) potentiated the anticancer effect of androgen-receptor inhibitors (ARis) in PC cells. SPH also induced transcriptional upregulation of ferritin heavy chain 1 (FTH1) in LNCaP and PC3 cell lines. Given the growing recognition that iron dysmetabolism plays a key role in PC, we applied the findings to this current study. Methods: Eight candidate FTH1-modulatory peptides (FT-001 to -008, all 7- or 8-mer peptides) were identified in the SPH peptide mix and subsequently sequenced and synthesized. Antiproliferative effects of individual FT peptides were assessed in combination with ARis (bicalutamide/BIC or enzalutamide/ENZ) in phenotypically distinct PC cell lines (LNCaP, PC3, VCaP, ENZR-VCaP) and compared to the inhibitory effect of SPH-ARi combination or ARi monotherapy. Results: FT-002 or -005 (10 μM concentration), showed significantly greater inhibition of LNCaP and PC3 cell viability when co-administered with BIC IC50 (0.4 μM & 10 μM respectively), than SPH (160 μM) with BIC or BIC monotherapy (p < 0.001). Similarly, either peptide combined with ENZ IC50 (1.4 μM) exhibited significant antiproliferative effects on androgen-sensitive VCaP cells when compared to SPH (160 μM) & ENZ co-treatment (p < 0.01) and ENZ monotreatment (p < 0.001). Both peptides (10 μM) produced a similar pattern of results in ENZ-resistant VCaP cells when treated with ENZ at its corresponding IC50 (47 μM) (p < 0.001). Differential gene expression profiling of all tested cells showed a consistent and significant upregulation of FTH1 and concomitant downregulation of transferrin receptor (TFRC) gene expression of greater than 2-fold for FT/ARi therapy. Conclusions: FT-002 and -005 synergistically combine with ARis to significantly attenuate PC tumor growth in vitro. Gene expression profiling implicates peptide-mediated FTH1 and TFRC modulation in the mode of action to interfere with tumor cell iron metabolism. Novel research perspectives implicate ferritin and FTH1 expression levels in prostate carcinogenesis and tumor progression. Further research in xenograft models is warranted, in order to validate the current findings and further investigate the cellular pathways responsible for the observed anticancer activity seen with FT-002 and FT-005.