HS1 protein role in regulating mechanical properties of Chronic Lymphocytic Leukaemia cells

Chronic lymphocytic leukaemia (CLL) is one of the most common and incurable B cell leukaemia. CLL cells traffic between peripheral blood, bone marrow and secondary lymphatic tissues where interact with the microenvironment. These processes are affected by the mechanical-forces present in the environment and by the capability of the cells to sense the forces. In this context we demonstrated that Hematopoietic-cell-specific Lyn-substrate-1 (HS1) protein is a cytoskeletal regulator and a prognostic factor in CLL. We proved that interfering with HS1 expression impacts on the progression and homing of CLL cells. To further study HS1 role in CLL we knocked-down HS1 expression by CRISPR/CAS9 technology in a CLL cells line (MEC1). By RNAseq and network analysis on MEC1HS1ko vs MEC1UT we found that HS1-KO significantly affects the expression of molecules involved in: cell motility, adhesion, cell-cell communication, focal adhesion formation. In particular, we found LEF1, FAK and Cortactin genes are up-regulated in MEC1HS1ko, suggesting their involvement in the mechano-signalling pathway. To study the nano-mechanical properties of those cells we are performing AFM measurements of single cell. The results provide an evaluation of the cell stiffness that is related to its deformation in response to an externally applied force. By AFM we found that MEC1HS1ko cells are less stiff if compared with MEC1UT cells. This results demonstrates a putative role for HS1 in regulating the mechanical properties of CLL cells. Due to the prognostic value of HS1 we are currently performing AFM measurement on selected patients and healthy B cells. We are planning to study in depth the role of HS1 in regulating the mechanical properties of the leukemic cells and how this contributes to leukemia development, progression and resistance to therapy.