- TUMORS HARVESTED FROM LSP1 KO MICE HAVE A LOWER FREQUENCY OF TOTAL LEUCOCYTES DUE TO MIGRATION DEFECTS

Tucumán

Congreso; LXVII Reunión Científica Anual de la Sociedad Argentina de Inmunología; 2019

Leukocyte-specific protein 1 (LSP1) is a 52kDa cytoplasmic F-actin binding phosphoprotein expressed in all human and murine leukocytes as well as in endothelial cells. This protein in known as an important regulator of actin cytoskeleton remodeling. It was reported that LSP1 polymorphisms or downregulation are considered risk factors for some types of cancer.We previously shown that tumors in Lsp1-/- mice grew significantly faster and bigger than in wild type (WT) controls. In order to study the role of LSP1 in antitumor immune response, we employed the B16-OVA melanoma model. WT and Lsp1-/- mice were subcutaneously-injected injected with 105 B16-OVA cells and followed-up until day 15.Tumors were analyzed by flow cytometry, showing a lower frequency of total infiltrating leukocytes (CD45+ cells) in tumors obtained from Lsp1-/- mice compared to their WT counterpart (p<0.01). Nonetheless, the leukocyte subpopulations proportions were similar in both animal groups.Considering that LSP1 is expressed by leukocytes and endothelial cells, an in vivo migration assay was performed. We observed a lower frequency of LSP1 KO migrant leukocytes in tumors developed in Lsp1-/- mice but not in WT mice (p<0.05). However, no difference in migrant cells was found when spleens or tumor draining lymph nodes were analyzed.We hypothesize that the impaired control of melanoma growth in Lsp1-/- mice could be caused at least in part, by the lower frequency of total leukocytes in tumor. This event might be a result of a reduced extravasation efficiency of Lsp1-/- leukocytes, combined with a modified vessels structure.