[Heterogeneity of tumor cells in glioblastomas]

To comprehensively assess the functional molecular biological status of different tumor cell populations in glioblastoma samples.

The activity of Ki-67, Bcl-2, and BCL6 expression was determined in 20 tumor samples from patients with glioblastoma. After that, a spatial analysis of heterogeneity in the expression of these markers in different tumor cell populations was carried out using computer and software tools and calculating the percentage of cells (PC) expressing this marker (Ki-67 labeling index (LI)) and a modified histoscore in different cell clusters.

Analysis of heterogeneity in the distribution of Ki-67, Bcl-2, and BCL6 expression could identify five cell clusters differing in the expression level of the above-mentioned markers. The most active cluster was the perivascular one (the highest mean Ki-67 LI (22.23±1.4%) and histoscore (118.59±3.36%); BCL6 PC and histoscore (17.4±1.4 and 79.32±4.86%, respectively). The least proliferative activity was observed in the perinecrotic cluster (Ki-67 LI (6.83±0.5%) and histoscore (62.46±2.25%)), while the neighboring transient necrotic cluster displayed sufficiently active proliferative processes (Ki-67 LI (18.39±0.56%) and histoscore (112.65±2.76%)). In addition, the transient vascular cluster was noted for a low proliferative activity (Ki-67 LI (8.37±0.35%) and histoscore (75.48±2.04%)). Finally, the intermediate cluster was characterized by the mean values of all parameters (Ki-67 LI (10.68±0.39%) and histoscore (95.73±2.37%). It should be noted that the differences in the expression activity for markers in these clusters were statistically significant.

The perivascular cluster carries the greatest potential for tumor progression and recurrence, which agrees with the data available in the literature: the perivascular zone is the most important niche for glioma stem cells that make a considerable contribution to the malignant potential of glioblastoma. Tumor pathogenesis and morphogenesis are a complex interweaving of interrelated factors, the realization of which within the framework of a multi-level heterochronic pathological process leads to the segregation of tumor cells and to the appearance of separate cell populations described in this paper.