The prognostic value of 19S ATPase proteasome subunits in acute myeloid leukemia and other forms of cancer.

Introduction: The ubiquitin-proteasome system (UPS) is an intracellular organelle responsible for targeted protein degradation, which represents a standard therapeutic target for many different human malignancies. Bortezomib, a reversible inhibitor of chymotrypsin-like proteasome activity, was first approved by the FDA in 2003 to treat multiple myeloma and is now used to treat a number of different cancers, including relapsed mantle cell lymphoma, diffuse large B-cell lymphoma, colorectal cancer, and thyroid carcinoma. Despite the success, bortezomib and other proteasome inhibitors are subject to severe side effects, and ultimately, drug resistance. We recently reported an oncogenic role for non-ATPase members of the 19S proteasome in chronic myeloid leukemia (CML), acute myeloid leukemia (AML), and several different solid tumors. In the present study, we hypothesized that ATPase members of the 19S proteasome would also serve as biomarkers and putative therapeutic targets in AML and multiple other cancers. Methods: We used data from The Cancer Genome Atlas (TCGA) and the Clinical Proteomic Tumor Analysis Consortium (CPTAC) available at UALCAN and/or GEPIA2 to assess the expression and prognostic value of proteasome 26S subunit, ATPases 1-6 (PSMC1-6) of the 19S proteasome in cancer. UALCAN was also used to associate PSMC1-6 mRNA expression with distinct clinicopathological features. Finally, cBioPortal was employed to assess genomic alterations of PSMC genes across different cancer types. Results: The mRNA and protein expression of PSMC1-6 of the 19S proteasome were elevated in several cancers compared with normal controls, which often correlated with worse overall survival. In contrast, AML patients demonstrated reduced expression of these proteasome subunits compared with normal mononuclear cells. However, AML patients with high expression of PSMC2-5 had worse outcomes. Discussion: Altogether, our data suggest that components of the 19S proteasome could serve as prognostic biomarkers and novel therapeutic targets in AML and several other human malignancies.

19S Proteasome Subunits as Oncogenes and Prognostic Biomarkers in FLT3-Mutated Acute Myeloid Leukemia (AML).

26S proteasome non-ATPase subunits 1 (PSMD1) and 3 (PSMD3) were recently identified as prognostic biomarkers and potential therapeutic targets in chronic myeloid leukemia (CML) and multiple solid tumors. In the present study, we analyzed the expression of 19S proteasome subunits in acute myeloid leukemia (AML) patients with mutations in the FMS-like tyrosine kinase 3 (FLT3) gene and assessed their impact on overall survival (OS). High levels of PSMD3 but not PSMD1 expression correlated with a worse OS in FLT3-mutated AML. Consistent with an oncogenic role for PSMD3 in AML, shRNA-mediated PSMD3 knockdown impaired colony formation of FLT3+ AML cell lines, which correlated with increased OS in xenograft models. While PSMD3 regulated nuclear factor-kappa B (NF-κB) transcriptional activity in CML, we did not observe similar effects in FLT3+ AML cells. Rather, proteomics analyses suggested a role for PSMD3 in neutrophil degranulation and energy metabolism. Finally, we identified additional PSMD subunits that are upregulated in AML patients with mutated versus wild-type FLT3, which correlated with worse outcomes. These findings suggest that different components of the 19S regulatory complex of the 26S proteasome can have indications for OS and may serve as prognostic biomarkers in AML and other types of cancers.

Loss of G0/G1 switch gene 2 (G0S2) promotes disease progression and drug resistance in chronic myeloid leukaemia (CML) by disrupting glycerophospholipid metabolism.

Tyrosine kinase inhibitors (TKIs) targeting BCR::ABL1 have turned chronic myeloid leukaemia (CML) from a fatal disease into a manageable condition for most patients. Despite improved survival, targeting drug-resistant leukaemia stem cells (LSCs) remains a challenge for curative CML therapy. Aberrant lipid metabolism can have a large impact on membrane dynamics, cell survival and therapeutic responses in cancer. While ceramide and sphingolipid levels were previously correlated with TKI response in CML, the role of lipid metabolism in TKI resistance is not well understood. We have identified downregulation of a critical regulator of lipid metabolism, G0/G1 switch gene 2 (G0S2), in multiple scenarios of TKI resistance, including (1) BCR::ABL1 kinase-independent TKI resistance, (2) progression of CML from the chronic to the blast phase of the disease, and (3) in CML versus normal myeloid progenitors. Accordingly, CML patients with low G0S2 expression levels had a worse overall survival. G0S2 downregulation in CML was not a result of promoter hypermethylation or BCR::ABL1 kinase activity, but was rather due to transcriptional repression by MYC. Using CML cell lines, patient samples and G0s2 knockout (G0s2-/- ) mice, we demonstrate a tumour suppressor role for G0S2 in CML and TKI resistance. Our data suggest that reduced G0S2 protein expression in CML disrupts glycerophospholipid metabolism, correlating with a block of differentiation that renders CML cells resistant to therapy. Altogether, our data unravel a new role for G0S2 in regulating myeloid differentiation and TKI response in CML, and suggest that restoring G0S2 may have clinical utility.

26S Proteasome Non-ATPase Regulatory Subunits 1 (PSMD1) and 3 (PSMD3) as Putative Targets for Cancer Prognosis and Therapy.

Ever since the ubiquitin proteasome system was characterized, efforts have been made to manipulate its function to abrogate the progression of cancer. As a result, the anti-cancer drugs bortezomib, carfilzomib, and ixazomib targeting the 26S proteasome were developed to treat multiple myeloma, mantle cell lymphoma, and diffuse large B-cell lymphoma, among others. Despite success, adverse side effects and drug resistance are prominent, raising the need for alternative therapeutic options. We recently demonstrated that knockdown of the 19S regulatory components, 26S proteasome non-ATPase subunits 1 (PSMD1) and 3 (PSMD3), resulted in increased apoptosis of chronic myeloid leukemia (CML) cells, but had no effect on normal controls, suggesting they may be good targets for therapy. Therefore, we hypothesized that PSMD1 and PSMD3 are potential targets for anti-cancer therapeutics and that their relevance stretches beyond CML to other types of cancers. In the present study, we analyzed PSMD1 and PSMD3 mRNA and protein expression in cancerous tissue versus normal controls using data from The Cancer Genome Atlas (TCGA) and the Clinical Proteomic Tumor Analysis Consortium (CPTAC), comparing expression with overall survival. Altogether, our data suggest that PSMD1 and PSMD3 may be novel putative targets for cancer prognosis and therapy that are worthy of future investigation.

Outcomes of an underserved Hispanic population with chronic hepatitis C treated with pegylated-interferon and ribavirin in a government-sponsored clinic.

OBJECTIVE: Treatment of hepatitis C virus (HCV) with interferon-based therapy has been shown to be less effective in Hispanics when compared to other populations. A pilot clinic was established at the University of Puerto Rico for the treatment of HCV in the government-insured population. The aim of this study was to describe the outcomes and treatment response to pegylated interferon and ribavirin in treatment-naive patients enrolled at this government-sponsored clinic. METHODS: A retrospective analysis was undertaken to investigate the treatment outcomes with weight based peg-interferon-alpha-2b and ribavirin in patients with chronic HCV enrolled in the pilot clinic during 2003-2005. Descriptive statistics were reported. Continuous variables were summarized as means and standard deviations. Frequency distributions and percents were used for categorical variables. Statistical analysis was performed using STATA. RESULTS: A total of 155 patients (105 males and 50 females) with mean age of 42 years started treatment; 79 (51%) patients had HCV genotype 1. Completion of treatment was achieved by 59 patients (38.1%), of whom end of treatment response (ETR) was observed in 30 (50.9%), representing 19.4% of the intention-to-treat population (ITT). Sustained viral response (SVR) was achieved in 17 (28.8%) patients who completed treatment, resulting in 11% (17/155) SVR by ITT. The only significant predictor of SVR was treatment onset within 5 years of the diagnosis of HCV (p = 0.026). Although no association was found between HCV genotype and SVR (p = 0.192), those patients with HCV genotypes 2 and 3 were more likely to complete treatment (p = 0.009). CONCLUSION: SVR to pegylated interferon and ribavirin seems to be lower than expected in our population. The high rate of incomplete treatment surpasses previously reported rates in U.S. Latinos and Caucasians. Further studies should explore reasons for lower response and higher treatment discontinuation in our population.

A government sponsored clinic for the evaluation and treatment of chronic hepatitis C in an underinsured population in Puerto Rico.

BACKGROUND: Chronic hepatitis C (CHC) is a major health problem in Puerto Rico (PR). More than 50% of the population is insured by a government-sponsored managed care system that does not cover treatment for CHC. Lack of access to treatment will result in an increase in end-stage liver disease with its high socioeconomic impact in the future. In an attempt to identify strategies for the treatment of CHC in the publicly insured population, the PR Health Department and the University of Puerto Rico (UPR) Gastroenterology (GI) Division have developed a pilot clinic for the evaluation and treatment of CHC. METHODS: UPR and the PR Health Department negotiated a fee per patient to include all medical care and follow-up laboratories. Viral studies were covered by a grant to the Health Department. Medications were bought at a discount price by the government and dispensed at a government pharmacy. The Health Department allocated funds for 200 patients with government insurance. A dedicated clinic was established at the UPR, staffed by an internist under the supervision of the GI faculty. Patients with a positive HCVab were referred to this clinic. The public insurance covered the CBC, liver tests, metabolic panel, TSH, HBsAg, HIV, ultrasound and liver biopsy, which were required prior to evaluation for possible treatment. In the initial visit, patients underwent a medical evaluation, including assessment of suitability for therapy and counseling. Those deemed to be candidates who still needed a liver biopsy had it performed by the GI staff. Genotype and viral titers were ordered after the decision on treatment had been made. The clinic physician prescribed pegylated interferon and ribavirin, which were dispensed by the government pharmacy. Instruction on proper drug administration was given. Clinic visits were scheduled for 1, 3, 6 and 12 months but also allowed on demand. Laboratory tests were done at the clinic and reviewed by the physician expediently to monitor for toxicity. Any medical problems or treatment for complications of therapy were covered by the primary insurer. Viral load was repeated at 12 weeks to discontinue therapy in those unlikely to respond. The budget per patient for medical visits and laboratory tests was dollars 1,500.00, HCV RNA titers plus genotype costs dollars 200.00, and HCV qualitative RNA costs dollars 123.00 RESULTS: 405 patients have been referred between February 2002 and April 2003 (the number was increased at adjust for no-shows and those not treated). 30% are female, the major risk factor is IVDU, and 80% are unemployed. 101 have started treatment and 48 are awaiting biopsy. A support group has been established at the clinic. CONCLUSIONS: The treatment for CHC in practice is not only costly but also resource consuming. Most gastroenterologists in our community refer these patients for treatment. The establishment of a dedicated clinic with a primary physician supervised by the specialists reduces costs and facilitates caring for a larger number of patients. The volume of services allows for negotiation of medical, laboratory and drug costs. In allocating funds for this project, the PR Health Department recognized the importance in reducing the potential spread in the community by treating infected patients as well as reducing the future medical and socioeconomic burden of end-stage liver disease. Although the outcome of this project is still unseen, we believe that this model may serve to establish other clinics for the treatment of CHC at lower costs with the same effectiveness.