Preclinical models of breast cancer: Two-way shuttles for immune checkpoint inhibitors from and to patient bedside.

The Food and Drug Administration has lately approved atezolizumab, anti-programmed death ligand 1 (PD-L1), to be used together with nanoparticle albumin-bound (nab) paclitaxel in treating patients with triple negative breast cancer (BC) expressing PD-L1. Nonetheless, immune checkpoint inhibitors (ICIs) are still challenged by the resistance and immune-related adverse effects evident in a considerable subset of treated patients without conclusive comprehension of the underlying molecular basis, biomarkers and tolerable therapeutic regimens capable of unleashing the anti-tumour immune responses. Stepping back to preclinical models is thus inevitable to address these inquiries. Herein, we comprehensively review diverse preclinical models of BC exploited in investigating ICIs underscoring their pros and cons as well as the learnt and awaited lessons to allow full exploitation of ICIs in BC therapy.

Extracellular ATP induces apoptosis through P2X7R activation in acute myeloid leukemia cells but not in normal hematopoietic stem cells.

Recent studies have shown that high ATP levels exhibit direct cytotoxic effects on several cancer cells types. Among the receptors engaged by ATP, P2X7R is the most consistently expressed by tumors. P2X7R is an ATP-gated ion channel that could drive the opening of a non-selective pore, triggering cell-death signal. We previously demonstrated that acute myeloid leukemia (AML) cells express high level of P2X7R. Here, we show that P2X7R activation with high dose ATP induces AML blast cells apoptosis. Moreover, P2X7R is also expressed on leukemic stem/progenitor cells (LSCs) which are sensitive to ATP-mediated cytotoxicity. Conversely, this cytotoxic effect was not observed on normal hematopoietic stem/progenitor cells (HSCs). Notably, the antileukemic activity of ATP was also observed in presence of bone marrow stromal cells and its addition to the culture medium enhanced cytosine arabinoside cytotoxicity despite stroma-induced chemoresistance. Xenotransplant experiments confirmed ATP antineoplastic activity in vivo.Overall, our results demonstrate that P2X7R stimulation by ATP induced a therapeutic response in AML at the LSC level while the normal stem cell compartment was not affected. These results provide evidence that ATP would be promising for developing innovative therapy for AML.

Therapeutic effect of lenalidomide in a novel xenograft mouse model of human blastic NK cell lymphoma/blastic plasmacytoid dendritic cell neoplasm.

PURPOSE: Blastic natural killer (NK) cell lymphoma/blastic plasmacytoid dendritic cell neoplasm (BNKL) is a rare and aggressive neoplasia characterized by infiltration of blast CD4(+)/CD56(+) cells in the skin, the bone marrow, and peripheral blood. Currently, more efforts are required to better define molecular and biological mechanisms associated with this pathology. To the best of our knowledge, no mouse model recapitulated human BNKL so far. EXPERIMENTAL DESIGN: Primary bone marrow cells from a BNKL patient were injected in nonobese diabetes/severe combined immunodeficient interleukin (IL) 2rγ(-/-) mice with the intent to generate the first BNKL orthotopic mouse model. Moreover, because of the lack of efficient treatments for BNKL, we treated mice with lenalidomide, an immunomodulatory and antiangiogenic drug. RESULTS: We generated in mice a fatal disease resembling human BNKL. After lenalidomide treatment, we observed a significant reduction in the number of peripheral blood, bone marrow, and spleen BNKL cells. Tumor reduction parallels with a significant decrease in the number of circulating endothelial and progenitor cells and CD31(+) murine endothelial cells. In mice treated with lenalidomide, BNKL levels of active caspase-3 were significantly augmented, thus showing proapoptotic and cytotoxic effects of this drug in vivo. An opposite result was found for proliferating cell nuclear antigen, a proliferation marker. CONCLUSIONS: Our BNKL model might better define the cellular and molecular mechanisms involved in this disease, and lenalidomide might be considered for the future therapy of BNKL patients.

Targeting activin receptor-like kinase 1 inhibits angiogenesis and tumorigenesis through a mechanism of action complementary to anti-VEGF therapies.

Genetic and molecular studies suggest that activin receptor-like kinase 1 (ALK1) plays an important role in vascular development, remodeling, and pathologic angiogenesis. Here we investigated the role of ALK1 in angiogenesis in the context of common proangiogenic factors [PAF; VEGF-A and basic fibroblast growth factor (bFGF)]. We observed that PAFs stimulated ALK1-mediated signaling, including Smad1/5/8 phosphorylation, nuclear translocation and Id-1 expression, cell spreading, and tubulogenesis of endothelial cells (EC). An antibody specifically targeting ALK1 (anti-ALK1) markedly inhibited these events. In mice, anti-ALK1 suppressed Matrigel angiogenesis stimulated by PAFs and inhibited xenograft tumor growth by attenuating both blood and lymphatic vessel angiogenesis. In a human melanoma model with acquired resistance to a VEGF receptor kinase inhibitor, anti-ALK1 also delayed tumor growth and disturbed vascular normalization associated with VEGF receptor inhibition. In a human/mouse chimera tumor model, targeting human ALK1 decreased human vessel density and improved antitumor efficacy when combined with bevacizumab (anti-VEGF). Antiangiogenesis and antitumor efficacy were associated with disrupted co-localization of ECs with desmin(+) perivascular cells, and reduction of blood flow primarily in large/mature vessels as assessed by contrast-enhanced ultrasonography. Thus, ALK1 may play a role in stabilizing angiogenic vessels and contribute to resistance to anti-VEGF therapies. Given our observation of its expression in the vasculature of many human tumor types and in circulating ECs from patients with advanced cancers, ALK1 blockade may represent an effective therapeutic opportunity complementary to the current antiangiogenic modalities in the clinic.

Infusional fluorouracil, epirubicin, and cisplatin followed by weekly paclitaxel plus bevacizumab in locally advanced breast cancer with unfavorable prognostic features.

The objective of this study was to evaluate the clinical and biological activities of bevacizumab in combination with preoperative anthracyclines and taxane-based chemotherapy in locally advanced breast cancer selected for unfavorable prognostic features. Patients with cT2-4c, cN0-2, estrogen and progesterone receptors less than 10% of the cells or cT4d and any estrogen/progesterone receptors expression received four courses of ECF-chemotherapy (epirubicin, cisplatin, fluorouracil as continuous infusion) followed by three courses of weekly paclitaxel in combination with bevacizumab. Thirty patients were included in the study. An objective response, either complete or partial, was observed in 26 patients (87%; 95% confidence interval: 69-96%), stable disease was observed in two patients (7%), and two patients (7%) progressed. A pathological complete response was obtained in 10 patients (33%; 95% confidence interval: 17-53%). Side effects related to bevacizumab with grade >or=2 included headache and hypertension. A nonstatistical significant decrease in the median value of circulating endothelial cells was observed at surgery (3.0/microl vs. 5.7/microl, P=0.19). In conclusion, high rates of both clinical and pathological responses with anthracycline-containing chemotherapy followed by weekly paclitaxel plus bevacizumab were observed in locally advanced breast cancer with unfavorable prognostic features. A non-negligible rate of progressive disease was observed, suggesting careful monitoring of the patients. Further studies evaluating the potential benefit of bevacizumab in neoadjuvant treatment need to be tested.