Related expression of TRKA and P75 receptors and the changing copy number of MYC-oncogenes determine the sensitivity of brain tumor cells to the treatment of the nerve growth factor in combination with cisplatin and temozolomide.

Abstract

Oncological diseases are an urgent medical and social problem. The chemotherapy induces not only the death of the tumor cells but also contributes to the development of their multidrug resistance and death of the healthy cells and tissues. In this regard, the search for the new pharmacological substances with anticancer activity against drug-resistant tumors is of utmost importance. In the present study we primarily investigated the correlation between the expression of TrkA and p75 receptors with the nerve growth factor (NGF) and cisplatin or temozolomide sensitivity of anaplastic astrocytoma (AA), glioblastoma (GB) and medulloblastoma (MB) cell cultures. We then evaluated the changing of copy numbers of MYCC and MYCN and its correlation with cytotoxicity index (CI) in MBcells under NGF exposition. The primary cell cultures were obtained from the tumor biopsy samples of the patients with AA (n=5), GB (n=7) or MB (n=25) prior to radiotherapy and chemotherapy. The cytotoxicity effect of NGF and its combinations with cisplatin or temozolomide, the relative expression of TrkA and p75 receptors, its correlations with CI in AA, GB and MB primary cell cultures were studied by trypan blue cytotoxicity assay and immunofluorescence staining respectively. The effect of NGF on MYCC and MYCN copy numbers in MBcell cultures was studied by fluorescence in situ hybridization. We found that the expression of TrkA and p75 receptors (p=0.03) and its ratio (p=0.0004) depends on the sensitivity of AA and GBcells to treatment with NGF and its combinations with cisplatin or temozolomide. NGF reduces (p<0.05) the quantity of MBcells with six or eight copies of MYCN and three or eight copies of MYCC. Besides, NGF increases (p<0.05) the quantity of MBcells containing two copies of both oncogenes. The negative correlation (r=-0.65, p<0.0001) is established between MYCC average copy numbers and CI of NGF in MBcells. The relative expression of NGF receptors (TrkA/p75) and its correlation with CI of NGF and its combinations in AA and GBcells point to the mechanism involving a cell death signaling pathway. NGF downregulates (p<0.05) some increased copy numbers of MYCC and MYCN in the human MBcell cultures, and upregulates normal two copies of both oncogenes (p<0.05).