Macrozoobenthic Communities of the Piedmont and Lowland Watercourses of the Lower Amur Region

On the basis of 120 original stations, macrozoobenthic communities of rivers from two adjacent areas of the Lower Amur Region (Khabarovsk krai) have been described. Rivers basins are characterized by contrasting landscape conditions: the Anyuy River basin in the piedmonts of the Sikhote-Alin mountain range and the Simmi River basin on the Amur Lowland. About 250 taxa of macroinvertebrates have been found; 16 types of communities have been described. The principal differences in both benthic fauna and macrozoobenthic communities in the basins of the Anyuy River (cold-water rheophilic fauna as well as ritral and crenal communities predominate) and the Simmi River (warm-water limnophilic fauna and phytal communities predominate) are shown. We discuss the reasons for these differences, specific features of the fauna and communities of the whole region, and the biogeographical position of the region.     

Natural and chemotherapy-induced clonal evolution of tumors

Evolution and natural selection of tumoral clones in the process of transformation and the following carcinogenesis can be called natural clonal evolution. Its main driving factors are internal: genetic instability initiated by driver mutations and microenvironment, which enables selective pressure while forming the environment for cell transformation and their survival. We present our overview of contemporary research dealing with mechanisms of carcinogenesis in different localizations from precancerous pathologies to metastasis and relapse. It shows that natural clonal evolution establishes intratumoral heterogeneity and enables tumor progression. Tumors of monoclonal origin are of low-level intratumoral heterogeneity in the initial stages, and this increases with the size of the tumor. Tumors of polyclonal origin are of extremely high-level intratumoral heterogeneity in the initial stages and become more homogeneous when larger due to clonal expansion. In cases of chemotherapy-induced clonal evolution of a tumor, chemotherapy becomes the leading factor in treatment. The latest research shows that the impact of chemotherapy can radically increase the speed of clonal evolution and lead to new malignant and resistant clones that cause tumor metastasis. Another option of chemotherapy-induced clonal evolution is formation of a new dominant clone from a clone that was minor in the initial tumor and obtained free space due to elimination of sensitive clones by chemotherapy. As a result, in ~20% of cases, chemotherapy can stimulate metastasis and relapse of tumors due to clonal evolution. The conclusion of the overview formulates approaches to tumor treatment based on clonal evolution: in particular, precision therapy, prediction of metastasis stimulation in patients treated with chemotherapy, methods of genetic evaluation of chemotherapy efficiency and clonal-oriented treatment, and approaches to manipulating the clonal evolution of tumors are presented.