Ubiquitin proteasome system and autophagy associated proteins in human testicular tumors

Discovery of novel benzylquinazoline molecules as p97/VCP inhibitors

Introduction: Protein p97 is an extensively investigated AAA ATPase with various cellular activities, including cell cycle control, ubiquitin-proteasome system, autophagy, and NF-κB activation. Method: In this study, we designed, synthesized and evaluated eight novel DBeQanalogs as potential p97 inhibitors in vivo and in vitro. Results: In the p97 ATPase inhibition assay, compounds 6 and 7 showed higher potency than the known p97 inhibitors, DBeQ and CB-5083. Compounds 4-6 dramatically induced G0/G1 phase arrest in the HCT116 cells, and compound 7 arrested the cells in both G0/G1 and S phases. Western blots showed elevated levels of SQSTM/p62, ATF-4, and NF-κB in HCT116 cells with the treatment of compounds 4-7, confirming their role in inhibiting the p97 signaling pathway in cells. In addition, the IC₅₀ of compounds 4-6 against HCT116, RPMI-8226, and s180 proliferation were 0.24-6.9 µM with comparable potency as DBeQ. However, compounds 4-6 displayed low toxicity against the normal human colon cell line. Thus, compounds 6 and 7 were proved to be potential p97 inhibitors with less cytotoxicity. In vivo studies using the s180 xenograft model have demonstrated that compound 6 inhibited tumor growth, led to a significant reduction of p97 concentration in the serum and tumor, and indicated non-toxicity on the body weight and organ-to-brain weight ratios except for the spleen at the dose of 90 μmol/kg/day for 10 days. Furthermore, the present study indicated that compound 6 may not induce s180 mice myelosuppression often observed in the p97 inhibitors. Conclusion: Compound 6 displayed high binding affinity to p97, great p97 ATPase inhibition, selective cytotoxicity, remarkable anti-tumor effect, and upregulated safety, which improved the clinical potential of p97 inhibitors.

A Determination of p97/VCP (Valosin Containing Protein) and SVIP (Small VCP Interacting Protein) Expression Patterns in Human Testis

Background and Objectives: The ubiquitin proteosome system (UPS) is a non-lysosomal pathway that functions in all eukaryotes. The transport of polyubiquitinated proteins to proteosomes takes place via the p97/Valosin-containing protein (VCP) chaperone protein. The p97/VCP binds to polyubiquitinated proteins, allowing these proteins to reach the proteasome and, thus, their destruction. In the case of p97/VCP deficiency, ubiquitinated proteins accumulate in the cell cytoplasm, and their subsequent failure to break down produces various pathological conditions. Small VCP interacting protein (SVIP) and p97/VCP proteins have not been studied in human testicular tissues from different postnatal periods. Therefore, in our study, we aimed to examine the expression of SVIP and p97/VCP in postnatal human testicular tissues. Our study aimed to contribute to further studies on the use of these proteins as testicular cell biomarkers in cases of unexplained male infertility. Materials and Methods: Immunohistochemical studies with the aim of determining the expression of p97/VCP and SVIP proteins in neonatal, prepubertal, pubertal, adult, and geriatric human testis tissues were performed. Results: In testicular sections obtained from a neonatal group, p97/VCP and SVIP were localized in different testicular and interstitial cells, and the lowest expression was observed in this group. While the expressions of these proteins were low in the neonatal period, they increased gradually in the prepubertal, pubertal and adult periods. The expression of p97/VCP and SVIP, which peaked in adulthood, showed a significant decrease in the geriatric period. Conclusions: As a result, the expression of p97/VCP and SVIP correlated with the increase in age, but it decreased significantly in older groups.

Green Tea Epigallocatechin-3-Gallate Regulates Autophagy in Male and Female Reproductive Cancer

With a rich abundance of natural polyphenols, green tea has become one of the most popular and healthiest nonalcoholic beverages being consumed worldwide. Epigallocatechin-3-gallate (EGCG) is the predominant catechin found in green tea, which has been shown to promote numerous health benefits, including metabolic regulation, antioxidant, anti-inflammatory, and anticancer. Clinical studies have also shown the inhibitory effects of EGCG on cancers of the male and female reproductive system, including ovarian, cervical, endometrial, breast, testicular, and prostate cancers. Autophagy is a natural, self-degradation process that serves important functions in both tumor suppression and tumor cell survival. Naturally derived products have the potential to be an effective and safe alternative in balancing autophagy and maintaining homeostasis during tumor development. Although EGCG has been shown to play a critical role in the suppression of multiple cancers, its role as autophagy modulator in cancers of the male and female reproductive system remains to be fully discussed. Herein, we aim to provide an overview of the current knowledge of EGCG in targeting autophagy and its related signaling mechanism in reproductive cancers. Effects of EGCG on regulating autophagy toward reproductive cancers as a single therapy or cotreatment with other chemotherapies will be reviewed and compared. Additionally, the underlying mechanisms and crosstalk of EGCG between autophagy and other cellular processes, such as reactive oxidative stress, ER stress, angiogenesis, and apoptosis, will be summarized. The present review will help to shed light on the significance of green tea as a potential therapeutic treatment for reproductive cancers through regulating autophagy.

Valosin-Containing Protein (VCP)/p97: A Prognostic Biomarker and Therapeutic Target in Cancer

Valosin-containing protein (VCP)/p97, a member of the AAA+ ATPase family, is a molecular chaperone recruited to the endoplasmic reticulum (ER) membrane by binding to membrane adapters (nuclear protein localization protein 4 (NPL4), p47 and ubiquitin regulatory X (UBX) domain-containing protein 1 (UBXD1)), where it is involved in ER-associated protein degradation (ERAD). However, VCP/p97 interacts with many cofactors to participate in different cellular processes that are critical for cancer cell survival and aggressiveness. Indeed, VCP/p97 is reported to be overexpressed in many cancer types and is considered a potential cancer biomarker and therapeutic target. This review summarizes the role of VCP/p97 in different cancers and the advances in the discovery of small-molecule inhibitors with therapeutic potential, focusing on the challenges associated with cancer-related VCP mutations in the mechanisms of resistance to inhibitors.