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We show that HIV-1-infected patients have increased concentrations of circulating V␦1 T cells (2.2%-9.0% of T lymphocytes; healthy donors, 1.0%-2%) and, in some instances, V␦2 T cells (3.5%-4.8% vs 2.0%-3.3%). In these patients, both V␦1 and V␦2 T cells are CXCR3 ؉ CXCR4 ؉ , whereas in healthy donors CXCR4 was preferentially expressed on V␦1 T lymphocytes. ␥␦ T cells transmigrated across endothelial monolayers, in response to interferon-␥-inducing protein-10 (IP-10/CXCL10), stromal cell-derived factor-1 (SDF-1/CXCL12), or both, according to the expression of the specific receptors CXCR3 and CXCR4. Interestingly, 6Ckine/SLC/CCL21 was more effective than IP-10/CXCL10 on V␦1 CXCR3 ؉ cells, whereas V␦2 CXCR3 ؉ cells were driven more efficiently by IP-10/ CXCL10. IP-10/CXCL10-and SDF-1/ CXCL12-induced transmigration was dependent on phosphoinositide-3 kinase (PI-3K), as demonstrated by the use of the specific blockers wortmannin and LY294002 and by the activation of the downstream serine kinase Akt/PKB on ligation of CXCR3 and CXCR4. Occupancy of CXCR3, but not of CXCR4, led to CAMKII activation; accordingly, the CAMKII inhibitors KN62 and KN93 decreased IP-10/CXCL10-but not SDF-1/ CXCL12-driven transmigration. Finally, HIV-1 Tat, which is present in the serum of HIV-1-infected patients, interferes with the chemotactic activity of these chemokines because of the cysteine-rich domain of the protein, which contains CXC and CC chemokine-like sequences.

Notwithstanding current multimodal treatment, including surgery, radiotherapy and chemotherapy with temozolomide (TMZ), median survival of glioblastoma (GBM) patients is about 14 months, due to the rapid emergence of cell clones resistant to treatment. Therefore, understanding the mechanisms underlying chemoresistance is mandatory to improve treatments' outcome. We generated TMZ resistant cells (TMZ-R) from a GBM cell line and from cancer stem cell-enriched cultures isolated from human GBMs. We demonstrated that TMZ resistance is partially reverted by "drug wash-out" suggesting the contribution of epigenetic mechanisms in drug resistance and supporting the possibility of TMZ rechallenge in GBM patients after prior drug exposure. The expression of histone lysine demethylase genes (KDMs) was increased in TMZ-R cells compared to parental cells, and TMZ resistance or restored sensitivity was mimicked by over-expressing or inactivating KDM5A. Methylation and expression of O6-methylguanine-DNA methyltransferase (MGMT) and drug efflux mechanisms were not altered in TMZ-R cells compared to parental TMZ sensitive cells. TMZ-R cells transiently acquired morphologic and molecular characteristics of differentiated tumor cells, features that were lost after drug wash-out. In conclusion, we demonstrated that treatment-induced TMZ resistance in GBM involves epigenetic mechanisms in a subset of slow-cycling and transiently partially differentiated cells that escape drug cytotoxicity, overcome G2 checkpoint and sustain clonal growth. We found that TMZ-R cells are sensitive to histone deacethylase inhibitors (HDACi) that synergize with TMZ. This strong synergism could be exploited to develop novel combined adjuvant therapies for this rapidly progressing and invariably lethal cancer.

Interleukin‐2 (IL‐2)‐activated polyclonal or clonal NK cells lysed autologous antigen presenting cells (APC) through the engagement of the natural cytotoxicity receptors (NCR) NKp30 and NKp46. NK cell‐mediated cytolysis of APC correlated with the surface density of these NCR. Indeed, NK cell clones bearing low amounts of NKp30 and NKp46 did not lyse autologous APC, whereas NK cell clones with bright expression of these NCR efficiently killed autologous APC. Upon masking of NKp30 or NKp46 by specific monoclonal antibodies a strong reduction (by 50%) of APC lysis could be detected and the complete inhibition was achieved by the simultaneous masking of these NCR. Interestingly, NK cell‐mediated APC lysis was impaired by the phosphatidylinositol 3‐kinase (PI‐3 K) inhibitors LY294002 or wortmannin. Similarly, these drugs strongly reduced NK cell activation triggered by NKp30 or NKp46 in a re‐directed killing assay as well as the activation of Akt/PKB, substrate of PI‐3 K, induced by the engagement of these receptors. Altogether, these findings strongly suggest that NCR are responsible for the killing of autologous APC through the activation of PI‐3 K.