MicroRNA mediated therapeutic effects of natural agents in prostate cancer

BACKGROUND

Several natural products, extensively studied for their anticancer activities, have been found to play an efficient role in preventing prostate cancer (PCa). Recently many natural agents have been reported to modulate microRNAs (miRNAs), that are involved in cancer cell growth. The microRNAs are endogenous small noncoding ribonucleic acid molecules that regulate various biological processes through an elegant mechanism of post-transcriptional control of gene expression. Besides being involved in cancer initiation, progression, angiogenesis, inflammation, they have been reported to be responsible for chemoresistance, and radioresistance of tumors. The dysregulated miRNA expression has been associated with many cancers including PCa. Over the past several years, it has been found that natural agents are good regulators of miRNAs and have a role in PCa also. Understanding the molecular mechanisms involving miRNAs by natural agents could result in developing useful strategies to combat this deadly disease.

METHODS

In order to collect research articles, the PubMed search engine was used with keywords 'prostate cancer' and 'natural agents' and 2007 papers were retrieved, further refinement with keywords 'phytochemical' and 'prostate cancer' showed 503 papers. Data was collected from research articles, published from 2010 to 2021. From these, research articles showing miRNA-mediated mechanisms were selected.

RESULTS

In this review, we have summarized the information available on the modulation of miRNAs by natural agents, their derivatives, and various combinatorial strategies with chemo/radiation therapy for the mitigation of PCa.

CONCLUSIONS

Based on the current review of literature, it has been found that the use of natural agents is a novel approach for altering miRNA expression strongly associated with PCa development, recurrence and resistance.

Radiomodification of glyoxalase I in the liver and spleen of mice: adaptive response and split-dose effect

Glyoxalase system, particularly glyoxalase I (Gly I) plays an important role in regulation of cell division and is considered to be a metabolic indicator of cell proliferation. The glyoxalase system is likely to have a close link with cellular radiosensitivity. Therefore, we have examined the effect of adaptive and split-dose of y-rays on the activity of Gly I in the liver and spleen of mice. For the adaptive response studies, mice pre-treated with a conditioning dose of 0.5 Gy were given a challenging dose of 4 Gy at varying time intervals. In the split-dose studies, a dose of 4 Gy was delivered into two equal fractions and spaced at different time intervals. The results show that pre-exposure to a conditioning dose or the fractionation of total dose decreased the specific activity of Gly I in the liver and spleen of mice. The decreased activity of Gly I was suggestive of protective action induced by the conditioning dose and fractionation of dose. The similar pattern of radiation response of Gly I probably supported the possibility of involvement of a common pathway in the radiation-induced adaptive and split-dose effect. From these observations a close link between the Gly I and the adaptive-response as well as the split-dose effect is speculated. Since, the glyoxalase system is vital for a variety of biological functions including cell division and repair, the present findings may have relevance in understanding the dose-fractionation as well as the biological defence induced by low doses of radiations.

Post-exposure radioprotection by Chlorella vulgaris (E-25) in mice

Oral administration of an algal mutant C. vulgaris E-25, 1 hr before or immediately after exposure to sublethal gamma-rays increased the number of endogenous spleen colony forming units (E-CFU). The magnitude of radioprotection was dependent on both, the dose of C. vulgaris fed and the time of administration. An optimal E-CFU was observed when 500 mg/kg body wt. of C. vulgaris was fed 1 hr before or immediately after irradiation. Significant recovery was observed in the number of bone marrow cells and the spleen weight. LD50/30 for Chlorella pre- and post-treated mice were 8.66 and 9.0 Gy, respectively compared to the control value of 7.8 Gy. The dose reduction factor (DRF) was 1.11 and 1.15 for pre-treated and post-treated mice respectively.

Evaluation of radioprotective action of a mutant (E-25) form of Chlorella vulgaris in mice

The possible role of orally fed Chlorella vulgaris (E-25) in modulating the gamma-ray induced chromosomal damage in whole-body irradiated mice was evaluated using a micronucleus test. Different doses of E-25 were administered either chronically (once, twice or thrice a day for 28 days) or as single acute doses before/after irradiation. A significant radioprotective effect was observed in both acute and chronic pretreatments, but only at doses above 400 mg/kg body weight. However, in mice that received E-25 (500 mg/kg) three times a day for 28 days, there was no protective effect, and a significant loss in their body weight was observed. Interestingly, E-25 afforded significant radioprotection even when it was administered within 0.4 hr after irradiation.