Pharmacological Effects of Guava (Psidium guajava L.) Seed Polysaccharides: GSF3 Inhibits PC-3 Prostate Cancer Cell Growth through Immunotherapy In Vitro.

Hsiao-Chien Lin,Jin-Yuarn Lin

doi:10.3390/ijms22073631

Hsiao-Chien Lin, Jin-Yuarn Lin

Open Access

https://doi.org/10.3390/ijms22073631

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Abstract

The inhibitory effects of purified fractions isolated from guava seed polysaccharides (GSPS) including guava seed polysaccharide fraction 1 (GSF1), GSF2, and GSF3 on prostate cancer cells remain unclear. To clarify the anti-prostate cancer potential, GSPS, GSF1, GSF2, and GSF3 were isolated using Sepharose 6B gel filtration chromatography to assay their inhibitory effects on prostate PC-3 cell growth with direct action or indirect immunotherapy using either splenocyte conditioned media (SCM) or macrophage conditioned media (MCM). Correlations between cytokine profiles in the conditioned media and pro-apoptotic gene expression levels in the corresponding treated PC-3 cells were analyzed. Results showed that GSPS, GSF1, GSF2, and GSF3, particularly GSF3, through either direct action or indirect treatments using SCM or MCM, significantly (p < 0.05) inhibited PC-3 cell growth. GSF3 direct treatments increased pro-apoptotic Bax/anti-apoptotic Bcl-2 mRNA expression ratios in corresponding treated PC-3 cells. Either SCM or MCM cultured with GSF3 increased Fas mRNA expression levels in corresponding treated PC-3 cells. Both Th2-polarized and anti-inflammatory cytokine IL-10 either secreted in SCM or MCM were positively correlated with Fas mRNA expression levels in corresponding treated PC-3 cells. Our results suggest that GSF3 is a potent biological response modifier to decrease PC-3 cell growth through inducing apoptosis.

Highlights

The results further suggest that secretions by immune cells including splenocytes and macrophages, which may exist in the tumor microenvironment, may inhibit prostate cancer cell growth
The results showed that paclitaxel direct treatment at 2.5 μM slightly, but not significantly (p > 0.05), increased Fas mRNA expression levels in the treated PC-3 cells as compared to that of the vehicle control (Table 2)
splenocyte conditioned media (SCM) and macrophage conditioned media (MCM) cultured with guava seed polysaccharide fraction-3 (GSF3) increased

Summary

Introduction

Even though the link between inflammation and prostate cancer is not concluded, anti-inflammation therapy for prostate cancer may be an active research area. Studies indicate that particular cancers may be improved through modulating immune balance to reduce chronic inflammatory reactions with potent materials, such as polysaccharides and other active components, by either direct action or alternative cancer immunotherapy [2,3,4]. Cancer immunotherapy with diverse biological response modifiers (BRMs) including polysaccharides has been developed as a promising anti-cancer method for it could obviously improve adverse effects as a result of chemotherapy and radiotherapy [5]. As potent BRMs, polysaccharides that enhance immunity, but have a low cytotoxicity to host cells, attract much attention for their important role in cancer immunotherapy [3,6,7,8,9,10].

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