CD4+ T cells sustain aggressive chronic lymphocytic leukemia in Eµ-TCL1 mice through a CD40L-independent mechanism.

Chronic lymphocytic leukemia (CLL) is caused by the progressive accumulation of mature CD5+ B cells in secondary lymphoid organs. In vitro data suggest that CD4+ T lymphocytes also sustain survival and proliferation of CLL clones through CD40L/CD40 interactions. In vivo data in animal models are conflicting. To clarify this clinically relevant biological issue, we generated genetically modified Eµ-TCL1 mice lacking CD4+ T cells (TCL1+/+AB0), CD40 (TCL1+/+CD40-/-), or CD8+ T cells (TCL1+/+TAP-/-), and we monitored the appearance and progression of a disease that mimics aggressive human CLL by flow cytometry and immunohistochemical analyses. Findings were confirmed by adoptive transfer of leukemic cells into mice lacking CD4+ T cells or CD40L or mice treated with antibodies depleting CD4 T cells or blocking CD40L/CD40 interactions. CLL clones did not proliferate in mice lacking or depleted of CD4+ T cells, thus confirming that CD4+ T cells are essential for CLL development. By contrast, CD8+ T cells exerted an antitumor activity, as indicated by the accelerated disease progression in TCL1+/+TAP-/- mice. Antigen specificity of CD4+ T cells was marginal for CLL development, because CLL clones efficiently proliferated in transgenic mice whose CD4 T cells had a T-cell receptor with CLL-unrelated specificities. Leukemic clones also proliferated when transferred into wild-type mice treated with monoclonal antibodies blocking CD40 or into CD40L-/- mice, and TCL1+/+CD40-/- mice developed frank CLL. Our data demonstrate that CD8+ T cells restrain CLL progression, whereas CD4+ T cells support the growth of leukemic clones in TCL1 mice through CD40-independent and apparently noncognate mechanisms.

Exploiting B-cell Receptor Stereotypy to Design Tailored Immunotherapy in Chronic Lymphocytic Leukemia.

PURPOSE: Approximately 30% of patients with chronic lymphocytic leukemia (CLL) can be grouped into subsets with stereotyped B-cell receptor immunoglobulin (BcR IG) displaying remarkable similarity in the heavy complementarity-determining region 3 (VH CDR3). Here, we investigated whether the consensus VH CDR3 sequences from CLL stereotyped subsets can be exploited for immunotherapy approaches. EXPERIMENTAL DESIGN: Immunogenic epitopes from the consensus VH CDR3 sequence of the clinically aggressive subsets #1 and #2 and from Eµ-TCL1 mice, which spontaneously develop CLL with BcR IG stereotypy, were identified and used to generate specific HLA class I- and II-restricted T cells in vitro. T-cell reactivity was assayed in vitro as IFNγ production. Bone marrow-derived dendritic cells loaded with the peptides were used as vaccination strategy to restrain leukemia development in the Eµ-TCL1 mouse model. RESULTS: These stereotyped epitopes were naturally processed and presented by CLL cells to the VH CDR3-specific T cells. Furthermore, we validated the efficacy of VH CDR3 peptide-based immunotherapy in the Eµ-TCL1 transplantable mouse model. Immunization of mice against defined VH CDR3 peptide epitopes, prior to the challenge with the corresponding leukemia cells, resulted in the control of CLL development in a significant fraction of mice, and increased overall survival. CONCLUSIONS: Our data highlight the immunogenicity of stereotyped VH CDR3 sequences and support the feasibility and efficacy of their use for novel cancer vaccine in CLL. Such approach has the advantage to generate "off-the-shelf" therapeutic vaccines for relevant groups of patients belonging to stereotyped subsets.See related commentary by Seiffert, p. 659.

Interleukin-1 receptor-associated kinase 4 inhibitor interrupts toll-like receptor signalling and sensitizes chronic lymphocytic leukaemia cells to apoptosis.

Chronic lymphocytic leukaemia (CLL) cells are strongly influenced by microenvironmental signals through the activation of distinct membrane receptors including the B-cell receptor and toll-like receptors (TLR). Recapitulating TLR stimulation in vitro by treating CLL cells with the TLR9 ligand CpG can induce metabolic activation and protection from apoptosis. We hypothesized that interfering with TLR signalling may be beneficial for treating CLL, and we tested in preclinical studies the effect of a specific interleukin-1 receptor-associated kinase 4 (IRAK4) inhibitory small molecule on primary leukaemic cells isolated from the peripheral blood of patients. We observed that IRAK4, an upstream kinase of the TLR pathway, is expressed in patients with CLL, and lower IRAK4 mRNA levels associate with a better outcome. The specific IRAK4 inhibitor disrupted TLR signalling as assessed by reduction of the specific biomarkers NFKBIZ and interleukin-6 mRNAs, and restrained the protective effect of in vitro TLR stimulation on cell viability. To note, IRAK4 inhibitor induced p53 and triggered apoptosis. Co-treatment of CLL cells with increasing concentrations of IRAK4i and the Bruton tyrosine kinase inhibitor ibrutinib demonstrated a synergistic effect. Our results suggest that targetting IRAK4 may represent a novel approach in CLL and may be combined with other signalling inhibitors.

Sunitinib prevents cachexia and prolongs survival of mice bearing renal cancer by restraining STAT3 and MuRF-1 activation in muscle.

Tyrosine kinase inhibitors, affecting angiogenesis, have shown therapeutic efficacy in renal cell carcinoma (RCC). The increased overall survival is not fully explained by their anti-tumor activity, since these drugs frequently induce disease stabilization rather than regression. RCC patients frequently develop cachectic syndrome. We used the RXF393 human renal carcinoma xenograft that recapitulates the characteristics of the disease, including the growth in the mouse kidney (orthotopic implantation), and the induction of cachexia with subsequent premature death. Sunitinib prevents body weight loss and muscle wasting and significantly improves the survival of RXF393-bearing nude mice. The anti-cachectic effect was not associated to direct anti-tumor activity of the drug. Most relevant is the ability of sunitinib to reverse the cachectic phenotype and rescue the animals from the loss of fat tissue. Body weight loss is prevented also in mice bearing the C26 colon carcinoma, classically reported to induce cachexia in immunocompetent mice. Among the mechanisms, we herein show that sunitinib is able to restrain the overactivation of STAT3 and MuRF-1 pathways, involved in enhanced muscle protein catabolism during cancer cachexia. We suggest that off-target effects of angiogenesis inhibitors targeting STAT3 are worth considering as a therapeutic option for patients who develop cachexia, independently of their anti-tumor activity.

Chemotherapy counteracts metastatic dissemination induced by antiangiogenic treatment in mice.

The development of resistance and progressive disease after treatment with angiogenesis inhibitors is becoming a controversial issue. We investigated the experimental conditions that cause multireceptor tyrosine kinase inhibitors (RTKI) to augment metastasis and whether opportune combinations with chemotherapy could counteract this effect. The renal Renca-luc tumor was transplanted orthotopically in the kidney of Balb/c mice, which then were or were not nephrectomized. The Lewis Lung carcinoma (LLC) was transplanted in the tibial muscle of C57/Bl6 mice. Treatment with the RTKI sunitinib started at different stages of tumor progression, mimicking neoadjuvant or adjuvant settings. Combination studies with paclitaxel, doxorubicin, cisplatin, gemcitabine, and topotecan were done on the LLC model, using opportune regimens. In a neoadjuvant setting, sunitinib inhibited Renca-luc tumor growth, prolonging survival despite an increase in lung metastasis; treatment after primary tumor surgery (adjuvant setting) or on established metastasis prolonged survival and decreased metastasis. Sunitinib increased lung metastasis from mice bearing early-stage LLC, but did not affect established metastases (no acceleration) from advanced tumors. Combinations with doxorubicin, topotecan, gemcitabine, but not cisplatin and paclitaxel, counteracted the increase in metastasis from LLC, partly reflecting their antitumor activity. Histology analysis after sunitinib confirmed tumor vascular changes and increased hypoxia. Topotecan at suboptimal daily doses reduced sunitinib-related metastasis, reducing tumor hypoxia. Tyrosine kinase inhibitors, as sunitinib, can have adverse malignant effects mainly in the neoadjuvant setting. The addition of chemotherapy might influence metastasis, depending on each drug mechanism of action and its regimen of administration.