Patterns of Expression of H₂S-Producing Enzyme in Human Renal Cell Carcinoma Specimens: Potential Avenue for Future Therapeutics

Abstract

Background: Renal cell carcinoma (RCC) is the most common cancer of the kidney. The most common histotype is clear-cell (cc) RCC. Hydrogen sulfide (H 2 S) is an angiogenic and anti-apoptotic gasotransmitter that is elevated under pseudohypoxic conditions. H 2 S is endogenously produced by three enzymes: Cystathionine γ-lyase (CSE), cystathionine βsynthase (CBS), and 3-mercaptopyruvate sulfurtransferase (MPST). Seeing as increased expression of these enzymes has been observed in other human cancer types, this study aimed to quantify H 2 S-producing enzyme expression in human RCC samples and evaluate whether it correlated with clinical outcomes. Patients and Methods: Eighty-eight human kidney tissue specimens, with healthy and cancerous tissue components, were immunohistochemically stained for CSE, CBS, and MPST. The mean pixel intensity of positively stained areas was quantified. A retrospective analysis was conducted to obtain patient demographics, rates of metastasis/recurrence, and prognostic characteristics. Statistical correlations between enzyme expressions and subsequent patient outcomes were evaluated. Results: There was significantly greater expression of CSE, CBS, and MPST in cc-RCC compared to paired healthy tissue (p<0.0001). The difference in expression of CSE in cancerous versus normal tissue was significantly greater than that for CBS and MPST (p<0.0001 and p<0.01, respectively). Enzyme expression patterns in cancerous versus normal tissue did not correlate with nuclear grade, stage, histological type or cancer recurrence/metastasis. Conclusion: To our knowledge, this is the first report of the differential increase in expression of CSE, CBS, and MPST in human RCC. Although these patterns do not appear to correlate with cancer recurrence, metastasis, size or nuclear grade, their differential increase suggests a potential therapeutic target. Renal cell carcinoma (RCC) is the most common cancer of the kidney. It accounts for 80-90% of all kidney cancer cases and has a cancer-specific mortality rate of 30-40% (1, 2). Incidence rates of RCC have increased over the past few decades, and this is largely attributed to increased detection by diagnostic tools (1, 3). RCC is subdivided into various histotypes based on tumour morphology, genetic signature, clinical manifestation, and area of the nephron where the tumour is present. The most common type of RCC is clearcell (cc) RCC, accounting for 80% of all cases. Other types included papillary, chromophobe and others, which can be classified as non-cc-RCC (4).

Emerging roles of cystathionine β-synthase in various forms of cancer

“…Renal oncocytoma, renal urothelial carcinoma, and renal clear cell carcinoma clinical samples also showed increased CBS expression, as evidenced by immunohistochemical analysis [ 72 , 73 ]. In an earlier report, in renal clear cell carcinoma samples a clear increase in CBS expression was seen as a function of increasing tumor stage; Fuhrman IV samples had over 3-times more CBS than Fuhrman I stage samples [ 72 ].…”

“…In an earlier report, in renal clear cell carcinoma samples a clear increase in CBS expression was seen as a function of increasing tumor stage; Fuhrman IV samples had over 3-times more CBS than Fuhrman I stage samples [ 72 ]. However, in a subsequent report, CBS enzyme expression patterns in renal clear cell carcinoma versus normal tissue did not correlate with nuclear grade, stage, histological type or cancer recurrence/metastasis [ 73 ]. According to analysis of the renal clear cell adenocarcinoma; KIRC Dataset, the level of CBS expression does not affect clinical prognosis [ 55 ].…”

Cystathionine Gamma-Lyase Is Increased in Testicular Seminomas, Embryonal, and Yolk Sac Tumors

“…H 2 S is synthesized by three enzymes, cystathione β-synthase, CSE, and 3-mercaptopyruvate sulfurtransferase , (8). H 2 S and one or more of the enzymes that synthesize it are increased in several common human malignancies, including prostate, breast, colon, oral squamous cell, and renal cell carcinomas (9)(10)(11)(12)(15)(16)(17). A role for H 2 S or the enzymes that synthesize it in testicular cancer has not been previously examined.…”

“…Cystathionine gamma-lyase (CSE) catalyzes hydrogen sulfide (H 2 S) synthesis by the conversion of cystathionine to L-cysteine, yielding pyruvate, ammonia, and H 2 S (8). CSE is increased in several human malignancies (9)(10)(11)(12). Interestingly, CSE promotes tumor metastases in breast and prostatic cancer (9, 10).…”

TNFα regulates the expression of the CSE gene in HUVEC

“…In HUVECs, the high concentration (50 ng/ml) of TNFα and a longer treatment duration (6 h) downregulated CSE expression, which may reduce endogenous H 2 S production and induce the inhibition of vascular smooth muscle relaxation (38) resulting in reduced local blood flow (39). This may lead to the chronic insufficiency of blood supply to local tumor tissue, resulting in the induction of apoptosis (19) and in the prevention of tumor recurrence, this suggests a potential therapeutic target for tumor (40). These results demonstrated that the DNA sequence, GGGACATTCC, on the CSE gene promoter was directly associated with the transcriptional regulation of the CSE gene in mammalian cells treated with TNFα.…”