Proteasome inhibitors and their combination with antiandrogens: effects on apoptosis, cellular proliferation and viability of prostatic adenocarcinoma cell cultures

The crosstalk between ubiquitination and endocrine therapy

Endocrine therapy (ET), also known as hormone therapy, refers to the treatment of tumors by regulating and changing the endocrine environment and hormone levels. Its related mechanism is mainly through reducing hormone levels and blocking the binding of hormones to corresponding receptors, thus blocking the signal transduction pathway to stimulate tumor growth. However, with the application of ET, some patients show resistance to ET, which is attributed to abnormal accumulation of hormone receptors (HRs) and the production of multiple mutants of HRs. The targeted degradation of abnormal accumulation protein mediated by ubiquitination is an important approach that regulates the protein level and function of intracellular proteins in eukaryotes. Here, we provide a brief description of the traditional and novel drugs available for ET in this review. Then, we introduce the link between ubiquitination and ET. In the end, we elaborate the clinical application of ET combined with ubiquitination-related molecules. KEY MESSAGES: • A brief description of the traditional and novel drugs available for endocrine therapy (ET). • The link between ubiquitination and ET. • The clinical application of ET combined with ubiquitination-related molecules.

Knockdown of PSMC2 contributes to suppression of cholangiocarcinoma development by regulating CDK1

Cholangiocarcinoma (CCA) has been well known as the second most common primary tumor of hepatobiliary system. PSMC2 (proteasome 26S subunit ATPase 2) is a key member of the 19S regulatory subunit of 26S proteasome, responsible for catalyzing the unfolding and translocation of substrates into the 20S proteasome, whose role in CCA is totally unknown. In this study, the results of immunohistochemistry analysis showed the upregulation of PSMC2 in CCA tissues compared with normal tissues, which was statistically analyzed to be associated with CCA tumor grade. Subsequently, the loss-of-function study suggested that knockdown of PSMC2 significantly suppressed cell proliferation, cell migration, promoted cell apoptosis and arrested cell cycle distribution in vitro. The decreased tumorigenicity of CCA cells with PSMC2 knockdown was confirmed in vivo by using mice xenograft model. In PSMC2 knockdown cells, pro-apoptotic protein Caspase3 was upregulated; anti-apoptotic proteins such as Bcl-2 and IGF-II were downregulated; among EMT markers, E-cadherin was upregulated while N-cadherin and Vimentin were downregulated, by which may PSMC2 regulates cell apoptosis and migration. Furthermore, through RNA-seq and verification by qPCR, western blotting and co-IP assays, CDK1 was identified as the potential downstream of PSMC2 mediated regulation of CCA. PSMC2 and CDK1 showed mutual regulation effects on expression level of each other. Knockdown of PSMC2 could aggregate the influence of CDK1 knockdown on cellular functions of CCA cells. In summary, our findings suggested that PSMC2 possesses oncogene-like functions in the development and progression of CCA through regulating CDK1, which may be used as an effective therapeutic target in CCA treatment.

High expression of PSMC2 promotes gallbladder cancer through regulation of GNG4 and predicts poor prognosis

Gallbladder cancer (GBC) is a common malignant tumor of the biliary tract, which accounts for 80-95% of biliary tumors worldwide, and is the leading cause of biliary malignant tumor-related death. This study identified PSMC2 as a potential regulator in the development of GBC. We showed that PSMC2 expression in GBC tissues is significantly higher than that in normal tissues, while high PSMC2 expression was correlated with more advanced tumor grade and poorer prognosis. The knockdown of PSMC2 in GBC cells induced significant inhibition of cell proliferation, colony formation and cell motility, while the promotion of cell apoptosis. The construction and observation of the mice xenograft model also confirmed the inhibitory effects of PSMC2 knockdown on GBC development. Moreover, our mechanistic study recognized GNG4 as a potential downstream target of PSMC2, knockdown of which could aggravate the tumor suppression induced by PSMC2 knockdown in vitro and in vivo. In conclusion, for the first time, PSMC2 was revealed as a tumor promotor in the development of GBC, which could regulate cell phenotypes of GBC cells through the interaction with GNG4, and maybe a promising therapeutic target in GBC treatment.

Silencing of PSMC2 inhibits development and metastasis of prostate cancer through regulating proliferation, apoptosis and migration

Background

Prostate cancer is the most common malignant tumor of male genitourinary system, molecular mechanism of which is still not clear. PSMC2 (proteasome 26S subunit ATPase 2) is a key member of the 19S regulatory subunit of 26S proteasome, whose relationship with prostate cancer is rarely studied.

Methods

Here, expression of PSMC2 in tumor tissues or cells of prostate cancer was detected by qPCR, western blotting and immunohistochemical analysis. The effects of PSMC2 knockdown on cell proliferation, colony formation, cell migration, cell cycle and apoptosis were assessed by Celigo cell counting assay, colony formation assay, wound-healing assay, Transwell assay and flow cytometry, respectively. The influence of PSMC2 knockdown on tumor growth in vivo was evaluated by mice xenograft models.

Results

The results demonstrated that PSMC2 was upregulated in tumor tissues of prostate cancer and its high expression was significantly associated with advanced Gleason grade and higher Gleason score. Knockdown of PSMC2 could inhibited cell proliferation, colony formation and cell migration of prostate cancer cells, while promoting cell apoptosis and cell cycle arrest. The suppression of tumor growth in vivo by PSMC2 knockdown was also showed by using mice xenograft models. Moreover, the regulation of prostate cancer by PSMC2 may be mediated by Akt/Cyclin D1/CDK6 signaling pathway.

Conclusions

Therefore, our studies suggested that PSMC2 may act as a tumor promotor in the development and progression of prostate cancer, and could be considered as a novel therapeutic target for prostate cancer treatment.

Silencing of Proteasome 26S Subunit ATPase 2 Regulates Colorectal Cancer Cell Proliferation, Apoptosis, and Migration

OBJECTIVE

Colorectal cancer (CRC) remains a major cause of cancer-related death worldwide. Proteasome 26S subunit ATPase 2 (PSMC2) plays vital roles in regulating cell cycle and transcription and has been confirmed to be a gene potentially associated with some human tumors. However, the expression correlation and molecular mechanism of PSMC2 in CRC are still unclear. This study aimed to investigate the role of PSMC2 in malignant behaviors in CRC.

METHODS

The high protein levels of PSMC2 in CRC samples were identified by tissue microarray analysis. Lentivirus was used to silence PSMC2 in HCT116 and RKO cells; MTT and colony formation assay were performed to determine cell proliferation. Wound healing and Transwell assay were used to detect cell migration and invasion. Flow cytometry assay was applied to detect cell cycle and apoptosis.

RESULT

The results showed that, among the 96 CRC patients, the expression of PSMC2 was a positive correlation with the clinicopathological features of the patients with CRC. Furthermore, the low PSMC2 expression group showed a higher survival rate than the high PSMC2 expression group. The expression levels of PSMC2 in cancer tissue were dramatically upregulated compared with adjacent normal tissues. In vitro, shPSMC2 was designed to inhibit the expression of PSMC2 in CRC cells. Compared with shCtrl, silencing of PSMC2 significantly suppressed cell proliferation, decreased single cell colony formation, enhanced apoptosis, and accelerated G2 phase and/or S phase arrest.

CONCLUSION

Survival analysis indicated that high expression of PSMC2 in the CRC samples was associated with poorer survival rate than low expression of PSMC2, while the anti-tumor effect of PSMC2 silencing was also confirmed at the cellular level in vitro. Our results suggested that PSMC2 potentially worked as a regulator for CRC, and the silencing of PSMC2 may be a therapeutic strategy for CRC.

Biology and management of malignant pleural mesothelioma

Malignant mesothelioma is an aggressive tumour, with a poor prognosis and an increasing incidence as a result of widespread exposure to asbestos. The results of the treatments available are poor. Surgery and radiotherapy have a limited role in highly selected patients and systemic therapy is the only potential treatment option for the majority of patients. Despite some definite activity of the novel antifolates such as pemetrexed and raltitrexed, the results, even in combination with platinating agents, are still modest, with a median survival of approximately one year. The better understanding of the biology of mesothelioma makes the assessment of a number of targeted agents particularly interesting. Unfortunately, the targeted agents imatinib, gefitinib, erlotinib and thalidomide have been shown to be ineffective in unselected patients. Studies with anti-angiogenesis agents are ongoing. An improvement of the knowledge of major molecular pathways involved in malignant mesothelioma is needed in order to define proper targets for the systemic treatment of this disease.

Proteasome inhibitor PSI induces apoptosis in human mesothelioma cells

Malignant mesothelioma is an increasingly common tumor with an almost 100% mortality rate. It is refractory to conventional treatment. We have previously shown with SSH and microarray that the mRNA expression level of proteasome is higher in epithelioid mesothelioma cell lines than in sarcomatoid ones. This study evaluates the differential apoptotic effect of proteasome inhibitors on both of these mesothelioma sub-lines. Proteasome inhibitors show substantial anti-tumor activity in some tumor cells in vitro and in vivo, but the effects on mesothelioma cells has not been studied. The viability of mesothelioma cells was reduced in a dose- and time-dependent manner by the proteasome inhibitors tested; PSI was effective with a low dose, but higher concentrations were needed for calpain inhibitor I. The epithelioid mesothelioma cells are more sensitive to the inhibitors than the sarcomatoid ones, their IC50 after 24 h of treatment with PSI being 4 and 16 microm, respectively. Other mesothelioma cell lines show similar sensitivity. PSI seemed to decrease mesothelioma viability by inducing apoptosis, as verified by cell morphology, Western blotting analysis of caspase 3 cleavage, and flow-cytometric analysis. In conclusion, PSI, a representative agent that reduces viability and induces apoptosis of mesothelioma cells, might be useful in the treatment of patients with mesothelioma, especially of epithelioid phenotype.