[Renal cell carcinoma. Immunohistological study to the expression of the inactive form of the pyruvate kinase]

HMGCR inhibition stabilizes the glycolytic enzyme PKM2 to support the growth of renal cell carcinoma

Renal cell carcinoma (RCC) is responsible for most cases of the kidney cancer. Previous research showed that low serum levels of cholesterol level positively correlate with poorer RCC-specific survival outcomes. However, the underlying mechanisms and functional significance of the role of cholesterol in the development of RCC remain obscure. 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) plays a pivotal role in RCC development as it is the key rate-limiting enzyme of the cholesterol biosynthetic pathway. In this study, we demonstrated that the inhibition of HMGCR could accelerate the development of RCC tumors by lactate accumulation and angiogenesis in animal models. We identified that the inhibition of HMGCR led to an increase in glycolysis via the regulated HSP90 expression levels, thus maintaining the levels of a glycolysis rate-limiting enzyme, pyruvate kinase M2 (PKM2). Based on these findings, we reversed the HMGCR inhibition-induced tumor growth acceleration in RCC xenograft mice by suppressing glycolysis. Furthermore, the coadministration of Shikonin, a potent PKM2 inhibitor, reverted the tumor development induced by the HMGCR signaling pathway.

Tumor type M2 pyruvate kinase expression in metastatic renal cell carcinoma

The M2 isoenzyme of pyruvate kinase (M2-PK) is specifically expressed in tumor cells (TuM2-PK) and has been detected in the peripheral blood of patients with renal cell carcinoma (RCC). TuM2-PK is not useful as a biological marker in localized RCC. We analysed TuM2-PK in 68 patients with metastatic RCC after initial surgery and prior to or during chemoimmunotherapy of metastases. In 50 patients, the levels of TuM2-PK were measured during chemoimmunotherapy with interleukin-2, interferon-alpha2a and 5-fluorouracil for up to 8 months and were correlated to response as assessed by radiological imaging techniques. TuM2-PK was quantified with a commercially available enzyme linked immunosorbent assay kit using a cut off of 15 kU/l. In 48 of 68 patients (71%), TuM2-PK was elevated above the cut-off. TuM2-PK was significantly higher in G3 tumors than in G2 tumors. In 34 of 50 patients (68%) undergoing chemoimmunotherapy, a positive correlation between TuM2-PK values and response to treatment was observed. Based on these data, we would not recommend the routine clinical use of TuM2-PK in metastatic RCC at this point.