Suppressive effects of liquid crystal compounds on the growth of U937 human leukemic monocyte lymphoma cells

The cytotoxic properties of the LCs on the cell growth, cell cycle distribution, and cell signaling pathway of U937 human leukemic monocyte lymphoma cells were assessed by flow cytometry and western blot analysis. Some LCs showed cytostatic effects, suppressing cell growth via S-phase arrest and without apoptosis in U937 cells. To investigate the mechanisms of the LC-induced S-phase arrest, proteins relevant to cell cycle regulation were investigated by western blot analysis. The rate of LC-induced S-phase arrest was congruent with the decreased expression of MCM2, cyclin A, cyclin B, CDK2, phospho-CDK1 and Cdc25C. Observed changes in cell cycle distribution by LC treated might be caused by insufficient preparation for G2/M transition. Considering the structure of the LCs, the rod-like molecules displaying cytotoxicity against U937 cells possessed flexible spacers with no bulky polar group attached via the flexible spacer.Our results revealed that some LCs showed cytotoxic properties against non-solid type tumor human leukemic cells via LC-induced S-phase arrest and decreasing expression of several cell cycle related proteins.Chemotherapy can regulate the uncontrolled proliferation of abnormal cancer cells by using various types of drugs. The majority of chemotherapeutic drugs can be divided into categories, including the alkylating agents, antimetabolites, anthracyclines, plant alkaloids, topoisomerase inhibitors, monoclonal antibodies, and other antitumor agents [1-7]. Although several types of chemotherapeutic agents have been developed recently, such as molecular targetting drugs, the tyrosine kinase inhibitor Imatinib, only few drugs may result in complete recovery of cancer patients. Therefore, it is essential to develop novel drugs for cancer treatment.Liquid-crystalline compounds (LCs) are widely used in display media in televisions and personal computers. LCs are classified into various categories on the basis of their structural characteristics. One of the