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Intratumor heterogeneity inherent in the majority of human cancers is a major obstacle for a highly efficient diagnosis and successful prognosis and treatment of these diseases. Being a result of clonal diversity within the same tumor, intratumor heterogeneity can be manifested in variability of genetic and epigenetic status, gene and protein expression, morphological structure, and other features of the tumor. It is most likely that the appearance of this diversity is a source for the adaptation of the tumor to changes in microenvironmental conditions and/or a tool for changing its malignant potential. In any case, both processes result in the appearance of cell clones with different undetermined sets of hallmarks. In this review, we describe the heterogeneity of molecular disorders in various human tumors and consider modern viewpoints of its development including genetic and non-genetic factors of heterogeneity origin and the role of cancer stem cells and clonal evolution. We also systematize data on the contribution of tumor diversity to progression of various tumors and the efficiency of their treatment. The main problems are indicated in the diagnosis and therapy of malignant tumors caused by intratumor heterogeneity and possible pathways for their solution. Moreover, we also suggest the key goals whose achievement promises to minimize the problem of intratumor heterogeneity and to identify new prognostic, predictive, and target markers for adequate and effective treatment of cancer. [ABSTRACT FROM AUTHOR]

Aim. To investigate the expression of the TGFB1, TNF, CSF1, CSF2, VEGFA and HIF1A genes in the patients with invasive breast carcinoma of no special type considering the intratumoral morphological heterogeneity. Methods. The technology of laser capture microdissection PALM was used to isolate five types of morphological tumor structures from three patients with invasive carcinoma of no special type (IC NST), luminal A subtype, T1-2NxMx. The level of expression of the cytokine (TNF), growth factors (TGFB1, CSF1, CSF2, VEGFA) and the HIF1A genes was assessed in the samples obtained using quantitative real-time PCR. Results. The study demonstrated the absence of the expression of the growth factor CSF2 gene in tumor cells of IC NST, and the expression of the CSF1 gene, independent from the metastasis status and tumor structure type. The prevalence of the expression of the VEGFA and TGFB1 genes was revealed in the alveolar and solid structures along with the rare expression of the TNF gene. Conclusions. The expression of pre-metastatic niche genes in the tumors of patients with IC NST is heterogeneous. The hypoxia-mediated change in the cytokine gene expression may be expected in the alveolar and solid structures, which ultimately results in the formation of microenvironment, facilitating tumor growth and the formation of tumor metastatic potential. [ABSTRACT FROM AUTHOR]