Adoptive cell transfer therapy with ex vivo primed peripheral lymphocytes in combination with anti-PDL1 therapy effectively inhibits triple-negative breast cancer growth and metastasis.

BACKGROUND: Adoptive cell transfer cancer immunotherapy holds promise for treating disseminated disease, yet generating sufficient numbers of lymphocytes with anti-cancer activity against diverse specificities remains a major challenge. We recently developed a novel procedure (ALECSAT) for selecting, expanding and maturating polyclonal lymphocytes from peripheral blood with the capacity to target malignant cells. METHODS: Immunodeficient mice were challenged with triple-negative breast cancer cell lines or patient-derived xenografts (PDX) and treated with allogeneic or autologous ALECSAT cells with and without anti-PDL1 therapy to assess the capacity of ALECSAT cells to inhibit primary tumor growth and metastasis. RESULTS: ALECSAT mono therapy inhibited metastasis, but did not inhibit primary tumor growth or prolong survival of tumor-bearing mice. In contrast, combined ALECSAT and anti-PDL1 therapy significantly inhibited primary tumor growth, nearly completely blocked metastasis, and prolonged survival of tumor-bearing mice. CONCLUSIONS: Combined ALECSAT and anti-PDL1 therapy results in favorable anti-cancer responses in both cell line-derived xenograft and autologous PDX models of advanced triple-negative breast cancer.

PDX Models: A Versatile Tool for Studying the Role of Myeloid-Derived Suppressor Cells in Breast Cancer.

The pivotal role of myeloid-derived suppressive cells (MDSCs) in cancer has become increasingly apparent over the past few years. However, to fully understand how MDSCs can promote human tumor progression and to develop strategies to target this cell type, relevant models that closely resemble the clinical complexity of human tumors are needed. Here, we show that mouse MDSCs of both the monocytic (M-MDCS) and the granulocytic (PMN-MDSC) lineages are recruited to human breast cancer patient-derived xenograft (PDX) tumors in mice. Transcriptomic analysis of FACS-sorted MDSC-subpopulations from the PDX tumors demonstrated the expression of several MDSC genes associated with both their mobilization and immunosuppressive function, including S100A8/9, Ptgs2, Stat3, and Cxcr2, confirming the functional identity of these cells. By combining FACS analysis, RNA sequencing, and immune florescence, we show that the extent and type of MDSC infiltration depend on PDX model intrinsic factors such as the expression of chemokines involved in mobilizing and recruiting tumor-promoting MDSCs. Interestingly, MDSCs have been shown to play a prominent role in breast cancer metastasis, and in this context, we demonstrate increased recruitment of MDSCs in spontaneous PDX lung metastases compared to the corresponding primary PDX tumors. We also demonstrate that T cell-induced inflammation enhances the recruitment of MDSC in experimental breast cancer metastases. In conclusion, breast cancer PDX models represent a versatile tool for studying molecular mechanisms that drive myeloid cell recruitment to primary and metastatic tumors and facilitate the development of innovative therapeutic strategies targeting these cells.

Targeting two distinct epitopes on human CD73 with a bispecific antibody improves anticancer activity.

BACKGROUND: Immunosuppressive extracellular adenosine is generated by the enzymatic activity of CD73. In preclinical models, antibodies (Abs) targeting different epitopes on CD73 exert anticancer activity through distinct mechanisms such as inhibition of enzymatic activity, engagement of Fc receptors, and spatial redistribution of CD73. METHODS: Using controlled Fab arm exchange, we generated biparatopic bispecific antibodies (bsAbs) from parental anti-CD73 Abs with distinct anticancer activities. The resulting anticancer activity was evaluated using in vitro and in vivo models. RESULTS: We demonstrate that different anticancer activities can be combined in a biparatopic bsAb. Remarkably, the bsAb significantly improved the enzyme inhibitory activity compared with the parental Abs, which led to neutralization of adenosine-mediated T-cell suppression as demonstrated by proliferation and interferon gamma (IFN-γ) production and prolonged survival of tumor-bearing mice. Additionally, the bsAb caused more efficient internalization of cell surface CD73 and stimulated potent Fc-mediated engagement of human immune effector cells in vitro and in vivo. CONCLUSIONS: Our data collectively demonstrate that complementary anticancer mechanisms of action of distinct anti-CD73 Abs can be combined and enhanced in a biparatopic bsAb. The multiple mechanisms of action and superior activity compared with the monospecific parental Abs make the bsAb a promising candidate for therapeutic targeting of CD73 in cancer. This concept may greatly improve future Ab design.

Sustained compensatory p38 MAPK signaling following treatment with MAPK inhibitors induces the immunosuppressive protein CD73 in cancer: combined targeting could improve outcomes.

RAS-MAPK signaling promotes immune evasion and cancer cell survival, and MAPK inhibitors (MAPKis) are frequently used as cancer therapies. Despite progress elucidating the direct effects of MAPKi on immune cells, their indirect effect on the tumor microenvironment (TME) through changes in tumor cells remains incompletely understood. Here, we present evidence of a rapid compensatory response to MAPKi that is driven by sustained p38 MAPK signaling and by which cancer cells can upregulate the immunosuppressive protein CD73 to reduce the antitumor immune response. This compensatory response also results in decreased sensitivity toward MAPKi, and, accordingly, combining anti-CD73 antibodies and MAPKi significantly enhances the antitumor effect compared to single-agent treatment in vivo. Combining MAPKi and anti-CD73 was accompanied by significant alterations in intratumor immune cell composition, supporting the effect of MAPKi-induced CD73 expression on the TME. We show that high CD73 expression significantly correlates with worse outcome in MAPKi-treated colorectal cancer patients, highlighting the potential clinical importance of increased CD73 expression following MAPKi treatment. Our findings may explain the diminished effect of MAPKi in cancer patients and provides further rationale for combined anti-CD73 and MAPKi treatment.

Co-targeting CDK4/6 and AKT with endocrine therapy prevents progression in CDK4/6 inhibitor and endocrine therapy-resistant breast cancer.

CDK4/6 inhibitors (CDK4/6i) combined with endocrine therapy have shown impressive efficacy in estrogen receptor-positive advanced breast cancer. However, most patients will eventually experience disease progression on this combination, underscoring the need for effective subsequent treatments or better initial therapies. Here, we show that triple inhibition with fulvestrant, CDK4/6i and AKT inhibitor (AKTi) durably impairs growth of breast cancer cells, prevents progression and reduces metastasis of tumor xenografts resistant to CDK4/6i-fulvestrant combination or fulvestrant alone. Importantly, switching from combined fulvestrant and CDK4/6i upon resistance to dual combination with AKTi and fulvestrant does not prevent tumor progression. Furthermore, triple combination with AKTi significantly inhibits growth of patient-derived xenografts resistant to combined CDK4/6i and fulvestrant. Finally, high phospho-AKT levels in metastasis of breast cancer patients treated with a combination of CDK4/6i and endocrine therapy correlates with shorter progression-free survival. Our findings support the clinical development of ER, CDK4/6 and AKT co-targeting strategies following progression on CDK4/6i and endocrine therapy combination, and in tumors exhibiting high phospho-AKT levels, which are associated with worse clinical outcome.

Human cancer evolution in the context of a human immune system in mice.

Immunotherapy is one of the most promising cancer treatment modalities, but the lack of appropriate preclinical in vivo models hampers the development of novel immunotherapeutic strategies. Here, we studied the ability of transplanted human cancer cells to form primary tumors and metastasize in humanized immune system (HIS) mice created by transfer of CD34+ human hematopoietic stem cells. All tested transplanted cancer cell lines developed primary tumors that progressed nearly synchronously. Spontaneous lung and liver metastases developed from both orthotopic and ectopic transplanted cancer cells, and the ability to spread inversely correlated with the extent of CD8+ infiltration in the primary tumor. Further analysis revealed that interactions between the cancer model and the tumor-infiltrating lymphocytes created tumor microenvironments (TMEs) resembling clinical cancers. Some models were largely immune cell-excluding, while others appeared to develop adaptive resistance to immune-mediated destruction by increased expression of programmed death ligand 1 (PDL1) and recruitment of human regulatory T cells. Our data suggest that HIS mice may provide a promising in vivo tumor model for evaluating immune modulatory anticancer therapies. Moreover, our study identified different tumor models resembling specific types of human TMEs, rendering each beneficial for addressing disease-specific issues.