ICAP-1 loss impairs CD8+ thymocyte development and leads to reduced marginal zone B cells in mice

ICAP-1 regulates β1-integrin activation and cell adhesion. Here, we used ICAP-1-null mice to study ICAP-1 potential involvement during immune cell development and function. Integrin α4β1-dependent adhesion was comparable between ICAP-1-null and control thymocytes, but lack of ICAP-1 caused a defective single-positive (SP) CD8+ cell generation, thus, unveiling an ICAP-1 involvement in SP thymocyte development. ICAP-1 bears a nuclear localization signal and we found it displayed a strong nuclear distribution in thymocytes. Interestingly, there was a direct correlation between the lack of ICAP-1 and reduced levels in SP CD8+ thymocytes of Runx3, a transcription factor required for CD8+ thymocyte generation. In the spleen, ICAP-1 was found evenly distributed between cytoplasm and nuclear fractions, and ICAP-1–/– spleen T and B cells displayed upregulation of α4β1-mediated adhesion, indicating that ICAP-1 negatively controls their attachment. Furthermore, CD3+- and CD19+-selected spleen cells from ICAP-1-null mice showed reduced proliferation in response to T- and B-cell stimuli, respectively. Finally, loss of ICAP-1 caused a remarkable decrease in marginal zone B- cell frequencies and a moderate increase in follicular B cells. Together, these data unravel an ICAP-1 involvement in the generation of SP CD8+ thymocytes and in the control of marginal zone B-cell numbers

A model to investigate drug-tolerant persister and resistant cells in melanoma targeted with MAPK inhibitors

2 p.Introduction The BRAFV600E mutation in melanoma is generally associated with activation of the MAPK/ERK signaling pathway, leading to tumor cell proliferation. Targeted therapy with combined BRAFV600E and MEK inhibitors has improved patient survival, but resistance to this treatment is very frequent and represents a serious clinical challenge. Resistance can be intrinsic or can be based on newly-acquired genetic alterations. Moreover, drug tolerant/persister (DTP) clones arising without genetic changes from tumor cells that adapt and survive the initial phases of therapy, can be another source of resistance. The aim of our study is to characterize the mechanisms of resistance to MAPK-targeted therapy in melanoma.Material and Methods We have used the mouse melanoma YUMM cell model to in vitro and in vivo (C57BL/6 mice) generate cells resistant to combined BRAF and MEK inhibitors. Both putative DTP and resistant cell populations have been selected from the in vitro and in vivo platforms, and cell survival and proliferation, and cell signaling and function are being investigated.Results and Discussions DTP and resistant cells display significant changes in growth and in several signaling properties and transition markers, and potential gene differences are currently examined byRNAseq and their functional implications investigated.Conclusion Our in vitro and in vivo models represent useful platforms to mechanistically study drug adaptation and resistance mechanisms in DTP and resistant melanoma cell populations, as well as a system to assess new inhibitors targeting these populations.Peer reviewe