A b s t r a c tMelanoma is one of the most aggressive and resistant to treatment neoplasms. There are still many challenges despite many promising advances in anticancer treatment. Currently, the main problem for all types of treatment is associated with heterogeneity. Due to heterogeneity of cancer cells, "precise" targeting of a medicine against a single phenotype limits the efficacy of treatment and affects resistance to applied therapy. Therefore it is important to understand aetiology and reasons for heterogeneity in order to develop effective and long-lasting treatment. This review summarises roles of vascular endothelial growth factor (VEGF) that may stimulate growth of a melanoma tumour irrespective of its proangiogenic effects, contributing to cancer heterogeneity. VEGF triggers processes associated with extracellular matrix remodelling, cell migration, invasion, angiogenesis, inhibition of immune responses and favours phenotypic plasticity and epithelial-mesenchymal transition. Consequently, it participates in mechanisms of interactions between melanoma cancer cells and microenvironment and it can modify sensitivity to therapeutic factors.

Gynecological cancers constitute a serious problem in the world. Their advanced stages are often characterized by the accumulation of ascites, which leads to spreading of cancer cells outside their primary focus. Despite progress in the treatment, prognoses are still not satisfactory. The main causes of these failures are chemoresistance, metastases and recurrences of the disease, which is influenced by, among others, the microenvironment of cancer cells. This study investigated the effect of the microenvironment, which create ascites derived from patients with ovarian and endometrial cancer to non-gynecological HEK 293 cells. The effect of the gynecological cancer microenvironment on HEK 293 cells behaviour was analysed using RT-PCR, qRT-PCR, Western blotting and functional analysis (invasion assays, hanging drop) methods. Our results suggest that the key genes for the development of cancer can be regulated by epigenetic and hypoxiainducible factor in dependent manner. It was observed that in vitro microenvironment, which is created by cells originating from patients with gynecological cancer (ovarian cancer, endometrial cancer) is able to generate changes in HEK 293 cells by itself.