Visualization of the effect of TR100 anti-cancer compound on membrane nanotubes with SR-SIM microscopy

Abstract

One of the most dangerous diseases is cancer, nearly 2 million new cancer types are diagnosed each year, worldwide, causing most of the death. Therefore, cancer is in the focus of many types of research. To prevent the proliferation and spreading of malignant cells, several compounds have been developed in chemotherapy, however, a significant proportion of these have serious side effects, and resistance is commonly emerging early after administration. Tumor cells require tropomyosin-containing actin network for their growth and survival. The tropomyosin profile is considerably changed in cancers resulting in the dramatic rearrangements of the actin cytoskeleton structure, therefore anti-tropomyosin compounds can be a new perspective in cancer therapy, such as TR100 which was reported to be capable of destroying cancer cells in a highly tumor-specific manner by increasing the depolymerization of the actin filament. On the other hand tumor cells can commonly communicate with each other via membrane nanotubes (NTs) for which actin is essential for growth. Tumor cell NTs may transport not only signal molecules, or cell organelles, but resistance factors against chemotherapeutic agents to help to survive. Immune cells also frequently use membrane nanotubes for communication, therefore, in this study we focused on the visualization of the effect of TR100 on the morphology and formation of B lymphoma cell NTs with superresolution structured illumination microscopy. TR100 treatment caused spectacular changes on the NT forming capability and the morphology of B cells in a concentration dependent manner, while low concentration of the agent significantly promoted NT formation, and at the same time produced shorter and thicker tubes in the early stage of their formation, in higher concentration it affected mainly only the cells, causing the rounding and finally the death of them. We were not able to detect any significant change on cells with extended nanotubular network, suggesting that TR100 is a less potent candidate in anti-cancer therapy.