Aberrant expression of six apoptosis genes in kidney cancer

Abstract

Background. Kidney cancer remains one of the most aggressive and difficult to treat malignant tumors. Its characteristic asymptomatic course leads to late detection at stages where standard therapy methods lose their effectiveness, which requires the development of new therapeutic strategies targeting key molecular mechanisms of oncogenesis. One of these mechanisms is a violation of the regulation of apoptosis - programmed cell death, which normally serves as a natural barrier to uncontrolled proliferation and survival of damaged cells. Studying the expression of apoptosis regulatory genes not only reveals the mechanisms of carcinogenesis, but also opens up ways for developing new therapeutic approaches, such as the use of BH3-mimetics - small molecules that selectively inhibit anti-apoptotic proteins of the Bcl-2 family.

Aim. This work was to evaluate changes in the expression of key apoptotic genes (DAPK1, BCL2, BCL2L11/BIM, BCL2L4/BAX, BCL2L3/MCL1 and TP53) in tumor tissue compared to the expression of these genes in adjacent histologically normal kidney tissue.

Methods. In the study, we used paired samples of surgical biopsies (tumor / adjacent histologically normal tissue) from 45 patients diagnosed with clear cell renal cancer, which were collected and clinically characterized at the Research Institute of Clinical Oncology, Blokhin National Medical Research Center of Oncology. RNA was isolated using a standard method. The expression levels of the studied genes were analyzed using reverse transcription followed by real-time PCR on CFX 96 Bio-Rad thermal cycler. Statistical processing of the results was performed using the ANOVA test after assessing the normality of distribution in the Shapiro-Wilk test in the CFX Maestro 2.3 Bio-Rad software.

Results. A significant (p≤0.05) decrease in expression by 1.58-2.63 times by the median of BCL2L11/BIM, BCL2L4/BAX, BCL2L3/MCL1, DAPK1 and TP53 genes was shown in tumor tissue compared to adjacent histologically normal kidney tissue. Analysis of the expression of the apoptotic genes depending on the clinical and pathomorphological parameters showed that the studied genes demonstrated stage-dependent dynamics in kidney cancer. At the trend level, activation of the BCL2 gene was revealed at stage I and consistent restoration of the expression level of the BCL2L11/BIM and DAPK1 genes was shown from stage I to stage IV of the oncological process (p=0.051, p=0.085, p=0.062, respectively). A significant (p≤0.05) decrease in the expression of the BCL2 gene, as well as an increase in the expression level of the DAPK1 and TP53 genes in samples of tumors invading the renal capsule (T3-4) was shown compared to tumors located in the renal parenchyma (T1). Statistically significant data (p≤0.01) were obtained on an increase in the expression level by the median for the BCL2L4/BAX, BCL2L3/MCL1 genes in samples with lymphogenous metastasis by 22.22 and 46.82 times, respectively. The restoration of DAPK1 gene expression in tumor samples with metastases to distant organs and tissues of the body was shown at the trend level (0.1<p≤0.05).

Conclusion. The study confirms stage-dependent deregulation of apoptosis in kidney cancer with a predominance of anti-apoptotic signals at the early stages. Such a rearrangement in the expression of the studied genes is characteristic of epithelial-mesenchymal, and then mesenchymal-epithelial transitions. The data obtained substantiate future studies of the use of BH3-mimetics taking into account the features of the expression of apoptosis-associated genes in kidney cancer.