Suppression of the growth and invasiveness of human prostate cancer cells in vitro by neuropeptide antagonist substance P analogues

The effect of SP/NK1R on expression and activity of glutaredoxin and thioredoxin proteins in prostate cancer cells

Substance P (SP), an important neuropeptide, has a crucial role in the progression of several cancers, including prostate cancer, through interacting with the neurokinin-1 receptor (NK1R). Oxidative stress is also involved in the onset and progression of prostate cancer. However, no studies have been performed on the cross-talk between the SP/NK1R system and cellular redox balance in prostate cancer, and how it is involved in tumorogenesis. We aimed to investigate the effect of the SP/NK1R system and the blockage of NK1R with its specific antagonist (aprepitant) on the cellular redox status of the prostate cancer cell line (PC3 and LNCaP). We performed the resazurin assay to evaluate the toxicity of the aprepitant on the PC3 and LNCaP cell lines. The intracellular reactive oxygen species (ROS) level was measured after SP and aprepitant treatment. The alterations of expression and activity of two crucial cellular oxidoreductases, glutaredoxin, and thioredoxin were evaluated by qRT-PCR and commercial kits (ZellBio GmbH), respectively. Our results revealed that SP increased ROS production and decreased the expression and activity of glutaredoxin and thioredoxin. On the other hand, treatment of cells with aprepitant showed reverse results. In conclusion, we found that the SP/NK1R system could promote prostate cancer progression by inducing oxidative stress. In addition, the inhibition of NK1R by aprepitant modulated the effect of the SP/NK1R system on the cellular redox system. Aprepitant might therefore be introduced as a candidate for the treatment of prostate cancer; however, more studies are required to confirm the validation of this hypothesis.

The In Vitro Pro-inflammatory Functions of the SP/NK1R System in Prostate Cancer: a Focus on Nuclear Factor-Kappa B (NF-κB) and Its Pro-inflammatory Target Genes

Prostate cancer is one of the main global health threats for men which is in close association with chronic inflammation. Neuropeptide substance P (SP), acting through neurokinin receptor (NK-1R), induces various pro-inflammatory responses which are strongly involved in the pathogenesis of several diseases as well as cancer. Therefore, we aimed to investigate the pro-inflammatory functions of the SP/NK1R complex in prostate cancer and the therapeutic effects of its inhibition by NK-1R antagonist, aprepitant, in vitro. MTT assay was conducted for the cytotoxicity assessment of aprepitant in prostate cancer cells. The protein expression levels were evaluated by Western blot assay. Quantitative real-time PCR (qRT-PCR) was applied to measure mRNA expression levels of pro-inflammatory cytokines. Concurrently, the protein concentrations of pro-inflammatory cytokines were also analyzed by enzyme-linked immunosorbent assay. We observed that SP increased the levels of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α), while treatment with aprepitant reduced the effects of SP. We also indicated that SP increased the protein levels of nuclear factor-kappa B (NF-κB), as the main regulator of inflammatory processes, and also an NF-κB target gene, cyclooxygenase 2 (COX-2) in prostate cancer cells, while treatment with aprepitant reversed these effects. Taken together, our findings highlight the importance of the SP/NK1R system in the modulation of pro-inflammatory responses in prostate cancer cells and suggest that aprepitant may be developed as a novel anti-inflammatory agent for the management of cancer-associated inflammation.

SP/NK1R system regulates carcinogenesis in prostate cancer: Shedding light on the antitumoral function of aprepitant

AIMS

Prostate cancer continues to be one of the main global health issues in men. Neuropeptide substance P (SP) acting via neurokinin-1receptor (NK1R) promotes tumorigenicity in many human malignant tumors. However, its pro-tumorigenic functions and the therapeutic effects of its inhibition in prostate cancer remain unclear.

METHODS

MTT assay was employed for measuring cellular proliferation and cytotoxicity. mRNAs and proteins expression levels were evaluated by qRT-PCR and western blot assay, respectively. Gelatinase activity was assessed by zymography. The migration ability was defined using wound-healing assay. Flow cytometry was employed to evaluate the cell cycle distribution. We also performed an in vivo experiment in a mouse model of prostate cancer to confirm the in vitro therapeutic effect of targeting the SP/NK1R system.

RESULTS

We found a noticeable increase in the expression of the truncated isoform of NK1R as an oncogenic NK1R splice variant in tumor cells. We also demonstrated that SP promotes both proliferative and migrative phenotypes of prostate cancer through modifying cell cycle-related proteins (c-Myc, cyclin D1, cyclin B1, p21), and apoptosis-related genes (Bcl-2 and Bax), promoting cell migration and increasing MMP-2 and MMP-9 expression and activity, while aprepitant administration could remarkably reverse these effects. SP also stimulated tumor growth in vivo, which was correlated with shorter survival times, while aprepitant reversed this effect and led to significantly longer survival time.

SIGNIFICANCE

Our findings suggest that SP/NK1R system may serve as a novel therapeutic target in prostate cancer and support the possible candidacy of aprepitant in future prostate cancer therapy.

Dipeptidyl peptidase IV activity and/or structure homologues (DASH) and their substrates in cancer

Post-translational modification of proteins is an important regulatory event. Numerous biologically active peptides that play an essential role in cancerogenesis contain an evolutionary conserved proline residue as a proteolytic-processing regulatory element. Proline-specific proteases could therefore be viewed as important "check-points". Limited proteolysis of such peptides may lead to quantitative but, importantly, due to the change of receptor preference, also qualitative changes of their signaling potential. Dipeptidyl peptidase-IV (DPP-IV, EC 3.4.14.5, identical with CD26) was for many years believed to be a unique cell membrane protease cleaving X-Pro dipeptides from the N-terminal end of peptides and proteins. Subsequently, a number of other molecules were discovered, exhibiting various degree of structural homology and DPP-IV-like enzyme activity, capable of cleaving similar set of substrates. These comprise for example, seprase, fibroblast activation protein alpha, DPP6, DPP8, DPP9, attractin, N-acetylated-alpha-linked-acidic dipeptidases I, II and L, quiescent cell proline dipeptidase, thymus-specific serine protease and DPP IV-beta. It is tempting to speculate their potential participation on DPP-IV biological function(s). Disrupted expression and enzymatic activity of "DPP-IV activity and/or structure homologues" (DASH) might corrupt the message carried by their substrates, promoting abnormal cell behavior. Consequently, modulation of particular enzyme activity using e.g. DASH inhibitors, specific antibodies or DASH expression modification may be an attractive therapeutic concept in cancer treatment. This review summarizes recent information on the interactions between DASH members and their substrates with respect to their possible role in cancer biology.