Oxidative stress and redox signaling in CRPC progression: therapeutic potential of clinically-tested Nrf2-activators

Alpha-Lipoic Acid Reduces Cell Growth, Inhibits Autophagy, and Counteracts Prostate Cancer Cell Migration and Invasion: Evidence from In Vitro Studies

Alpha-lipoic acid (ALA) is a natural antioxidant dithiol compound, exerting antiproliferative and antimetastatic effects in various cancer cell lines. In our study, we demonstrated that ALA reduces the cell growth of prostate cancer cells LNCaP and DU-145. Western blot results revealed that in both cancer cells, ALA, by upregulating pmTOR expression, reduced the protein content of two autophagy initiation markers, Beclin-1 and MAPLC3. Concomitantly, MTT assays showed that chloroquine (CQ) exposure, a well-known autophagy inhibitor, reduced cells' viability. This was more evident for treatment using the combination ALA + CQ, suggesting that ALA can reduce cells' viability by inhibiting autophagy. In addition, in DU-145 cells we observed that ALA affected the oxidative/redox balance system by deregulating the KEAP1/Nrf2/p62 signaling pathway. ALA decreased ROS production, SOD1 and GSTP1 protein expression, and significantly reduced the cytosolic and nuclear content of the transcription factor Nrf2, concomitantly downregulating p62, suggesting that ALA disrupted p62-Nrf2 feedback loop. Conversely, in LNCaP cells, ALA exposure upregulated both SOD1 and p62 protein expression, but did not affect the KEAP1/Nrf2/p62 signaling pathway. In addition, wound-healing, Western blot, and immunofluorescence assays evidenced that ALA significantly reduced the motility of LNCaP and DU-145 cells and downregulated the protein expression of TGFβ1 and vimentin and the deposition of fibronectin. Finally, a soft agar assay revealed that ALA decreased the colony formation of both the prostate cancer cells by affecting the anchorage independent growth. Collectively, our in vitro evidence demonstrated that in prostate cancer cells, ALA reduces cell growth and counteracts both migration and invasion. Further studies are needed in order to achieve a better understanding of the underlined molecular mechanisms.

Metabolic changes during prostate cancer development and progression

Metabolic reprogramming has been recognised as a hallmark in solid tumours. Malignant modification of the tumour's bioenergetics provides energy for tumour growth and progression. Otto Warburg first reported these metabolic and biochemical changes in 1927. In prostate cancer (PCa) epithelial cells, the tumour metabolism also changes during development and progress. These alterations are partly driven by the androgen receptor, the key regulator in PCa development, progress, and survival. In contrast to other epithelial cells of different entities, glycolytic metabolism in prostate cells sustains physiological citrate secretion in the normal prostatic epithelium. In the early stages of PCa, citrate is utilised to power oxidative phosphorylation and fuel lipogenesis, enabling tumour growth and progression. In advanced and incurable castration-resistant PCa, a metabolic shift towards choline, amino acid, and glycolytic metabolism fueling tumour growth and progression has been described. Therefore, even if the metabolic changes are not fully understood, the altered metabolism during tumour progression may provide opportunities for novel therapeutic strategies, especially in advanced PCa stages. This review focuses on the main differences in PCa's metabolism during tumourigenesis and progression highlighting glutamine's role in PCa.

Attenuation of Pancreatic Cancer In Vitro and In Vivo via Modulation of Nrf2 and NF-κB Signaling Pathways by Natural Compounds

Pancreatic cancer is a disease in which deregulation of signaling pathways plays a key role, thus searching for their novel modulators is a promising therapeutic strategy. Hence, in this study, the effect of phytochemical combinations on the canonical and non-canonical activation of Nrf2 and its interaction with the NF-κB pathway was evaluated in extensively proliferating pancreatic cancer cell line, PSN-1, in comparison to non-cancerous MS1 cells. The activation of Nrf2 and NF-κB, expression of their target genes, and effect on cell survival were assessed in PSN-1 cells. The tumor burden was evaluated in mice carrying xenografts. PSN-1 cells were more sensitive to the tested compounds as compared to the MS1 cell line. Combination of xanthohumol and phenethyl isothiocyanate was more effective than single compounds at decreasing the canonical and non-canonical activation of Nrf2 in PSN-1 cancer cells. Decreased activation of NF-κB, and subsequent reduced cytosolic COX-2 and nuclear STAT3 level indicated their anti-inflammatory and pro-apoptotic activities. In vivo studies showed the partial response in groups treated with xanthohumol or the combination of xanthohumol and phenethyl isothiocyanate. Overall, these results suggest that the combination of xanthohumol and phenethyl isothiocyanate may be a promising therapeutic candidate against pancreatic cancer.