Considering the role played by the heat shock protein of 70 kDa (HSP70) in cancer, we characterized this protein and its major regulator, the heat shock factor 1 (HSF1), in chronic lymphocytic leukemia (CLL). We found both HSP70 and HSF1 overexpressed in CLL patients, correlated to poor prognosis and abnormally localized in the nucleus of leukemic B cells. The two proteins were strictly correlated each other and their levels decreased consensually in those patients responding to in vivo therapeutic regimens. HSP70 and HSF1 inhibition was proved to be effective in inducing a dose-dependent in vitro apoptosis of CLL B cells. Considering that HSF1 is finely regulated by kinases belonging to pathways triggered by rat sarcoma (RAS), we benefited from a previous proteomic study performed in CLL patients aiming to assess the activation/expression of key signaling proteins. We found that patients showing high levels of HSP70 also expressed high Akt-Ser473, thus activating HSF1. Inhibition of PI3K, which activates AKT, reduced the expression of HSF1 and HSP70. By contrast, HSP70-low patients displayed high activation of MEK1/2 and ERK1/2, known to negatively regulate HSF1. These data demonstrate that the HSP70 expression is regulated by the modulation of HSF1 activity through the activation of RAS-regulated pathways and suggest the HSP70/HSF1 interplay as an interesting target for antileukemic therapies. Finally, inhibition of PI3K, that activates AKT, reduced the expression of HSF1 and HSP70.

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BACKGROUND: Complex karyotype (CK) is a heterogeneous category with a negative impact in chronic lymphocytic leukaemia (CLL). Our group has recently reported that CK patients with major structural abnormalities (i.e. CK2) are characterised by a worse prognosis, as compared to other lesions within CK(CK1). METHODS: We performed a multicentre retrospective study to test whether the combination of CK subtypes with IGHV status could be a relevant prognostic and predictive tool. RESULTS: Among 522 patients 13% harboured CK2, 41% CK1 and/or U-IGHV (U-CK1) and 46% M-IGHV without any CK subtypes (M-noCK). After a median follow-up of 5.8 years, CK2 patients had the shortest TTFT (5-year TTFT 31%, 39 and 81%, p < 0.0001) and OS (5-year OS 67%, 85 and 93%, p < 0.0001) as compared to U-CK1 or M-noCK cases, regardless of TP53 abnormalities. CK2 patients also had the worst outcome after chemoimmunotherapy. In fact, the median TTNT after FCR or BR was 1.86 and 4.79 years for CK2 and U-CK1, but not reached for M-noCK patients (p < 0.0005). CONCLUSIONS: We herein suggest that the combined assessment of the IGHV mutational status and CK subtypes refines the prognostication of CLL, allowing to identify M-IGHV patients without any CK subtypes who are characterised by an indolent disease and excellent outcome after chemoimmunotherapy.

Cortactin (CTTN) is a substrate of the Src kinase Lyn that is known to play an actin cytoskeletal regulatory role involved in cell migration and cancer progression following its phosphorylation at Y421. We recently demonstrated that Cortactin is overexpressed in patients with chronic lymphocytic leukaemia (CLL). This work was aimed at defining the functional role of Cortactin in these patients. We found that Cortactin is variably expressed in CLL patients both in the peripheral blood and lymph nodes and that its expression correlates with the release of matrix metalloproteinase 9 (MMP-9) and the motility of neoplastic cells. Cortactin knockdown, by siRNA, induced a reduction in MMP-9 release as well as a decrease of migration capability of leukaemic B cells in vitro, also after chemotactic stimulus. Furthermore, Cortactin phosphorylation was lowered by the Src kinase-inhibitor PP2 with a consequent decrease of MMP-9 release in culture medium. An impaired migration, as compared to control experiments without Cortactin knockdown, was observed following CXCL12 triggering. Reduced Cortactin expression and phosphorylation were also detected both in vivo and in vitro after treatment with Ibrutinib, a Btk inhibitor. Our results highlight the role of Cortactin in CLL as a check-point molecule between the BCR and CXCR4 signalling pathways.