The prognostic value of regulatory T cells infiltration in HER2-enriched breast cancer microenvironment

Breast cancer represents a complex and heterogeneous disease that comprises distinct disease conditions, histological features, and clinical outcome. Since many years, it has been demonstrated as an association between HER2 amplification and poor prognosis, because its overexpression is associated with an aggressive phenotype of breast tumor cells. A significant proportion of cases have developed resistance to the current therapies available. Consequently, new prognostic markers are urgently needed to identify patients who are at the highest risk for developing metastases. During the past decade, new insights provided valuable knowledge regarding mechanisms underlying the dynamic interplayed between immune cells and tumor progression. It has been shown that the presence of a lymphocytic infiltrate, particularly of regulatory T cells, in cancer tissue, is associated with clinical outcome promoting rather than inhibiting cancer development and progression. It has been also verified that the clinical value of lymphocytic infiltration in breast cancers could be subtype-dependent, including the HER2-enriched subtype. In this context, this work summarizes proposed to discuss the prognostic value of regulatory T cell infiltration in microenvironment of HER2-enriched breast cancer.

Improved Survival of HER2+ Breast Cancer Patients Treated with Trastuzumab and Chemotherapy Is Associated with Host Antibody Immunity against the HER2 Intracellular Domain

The addition of trastuzumab to chemotherapy extends survival among patients with HER2(+) breast cancer. Prior work showed that trastuzumab and chemotherapy augments HER2 extracellular domain (ECD)-specific antibodies. The current study investigated whether combination therapy induced immune responses beyond HER2-ECD and, importantly, whether those immune responses were associated with survival. Pretreatment and posttreatment sera were obtained from 48 women with metastatic HER2(+) breast cancer on NCCTG (now Alliance for Clinical Trials in Oncology) studies, N0337 and N983252. IgG to HER2 intracellular domain (ICD), HER2-ECD, p53, IGFBP2, CEA, and tetanus toxoid were examined. Sera from 25 age-matched controls and 26 surgically resected HER2(+) patients were also examined. Prior to therapy, some patients with metastatic disease had elevated antibodies to IGFBP2, p53, HER2-ICD, HER2-ECD, and CEA, but not to tetanus toxin, relative to controls and surgically resected patients. Treatment augmented antibody responses to HER2-ICD in 69% of metastatic patients, which was highly associated with improved progression-free survival (PFS; HR = 0.5, P = 0.0042) and overall survival (OS; HR = 0.7, P = 0.038). Augmented antibody responses to HER2-ICD also correlated (P = 0.03) with increased antibody responses to CEA, IGFBP2, and p53, indicating that treatment induces epitope spreading. Paradoxically, patients who already had high preexisting immunity to HER2-ICD did not respond to therapy with increased antibodies to HER2-ICD and demonstrated poorer PFS (HR = 1.6, P < 0.0001) and OS (HR = 1.4, P = 0.0006). Overall, the findings further demonstrate the importance of the adaptive immune system in the efficacy of trastuzumab-containing regimens. Cancer Res; 76(13); 3702-10. ©2016 AACR.

Emerging immunotherapy strategies in breast cancer

Although immunogenicity is typically associated with renal cell carcinomas and melanoma, there are several compelling reasons why immune-based therapies should be explored in breast cancer. First, breast cancers express multiple putative tumor-associated antigens, such as HER-2 and MUC-1, which have been the successful focus of vaccine development over the past decade, translating into tumor-specific immune responses and, in some cases, clinical benefit. Second, passive immune strategies with anti-HER-2 antibodies, such as trastuzumab and pertuzumab, have led to survival benefits in breast cancer. Finally, the successes observed with novel immunotherapeutic strategies, such as immune checkpoint blockade and adoptive T-cell therapies in other malignancies, combined with a growing body of literature that supports an interplay between solid tumors and the immune system, indicate that these strategies have the potential to revolutionize the treatment of breast cancer.