Identification of an immune-suppressed subtype of feline triple-negative basal-like invasive mammary carcinomas, spontaneous models of breast cancer

Abstract

Feline invasive mammary carcinomas are characterized by their high clinical aggressiveness, rare expression of hormone receptors, and pathological resemblance to human breast cancer, especially triple-negative breast cancer (negative to estrogen receptor, progesterone receptor, and epidermal growth factor receptor type 2). Recent gene expression studies of triple-negative breast cancers have highlighted their heterogeneity and the importance of immune responses in their biology and prognostic assessment. Indeed, regulatory T cells may play a crucial role in producing an immune-suppressed microenvironment, notably in triple-negative breast cancers. Feline invasive mammary carcinomas arise spontaneously in immune-competent animals, in which we hypothesized that the immune tumor microenvironment also plays a role. The aims of this study were to determine the quantity and prognostic value of forkhead box protein P3-positive peritumoral and intratumoral regulatory T cells in feline invasive mammary carcinomas, and to identify an immune-suppressed subgroup of triple-negative basal-like feline invasive mammary carcinomas. One hundred and eighty female cats with feline invasive mammary carcinomas, treated by surgery only, with 2-year follow-up post-mastectomy, were included in this study. Forkhead box protein P3, estrogen receptor, progesterone receptor, Ki-67, epidermal growth factor receptor type 2, and cytokeratin 14 expression were assessed by automated immunohistochemistry. Peritumoral regulatory T cells were over 300 times more abundant than intratumoral regulatory T cells in feline invasive mammary carcinomas. Peritumoral and intratumoral regulatory T cells were associated with shorter disease-free interval and overall survival in both triple-negative (ER–, PR–, HER2–, N = 123 out of 180) and luminal (ER+ and/or PR+, N = 57) feline invasive mammary carcinomas. In feline triple-negative basal-like (CK14+) mammary carcinomas, a regulatory T-cell–enriched subgroup was associated with significantly poorer disease-free interval, overall survival, and cancer-specific survival than regulatory T-cell-poor triple-negative basal-like feline invasive mammary carcinomas. High regulatory T-cell numbers had strong and negative prognostic value in feline invasive mammary carcinomas, especially in the triple-negative basal-like subgroup, which might contain a “basal-like immune-suppressed” subtype, as described in triple-negative breast cancer. Cats with feline invasive mammary carcinomas may thus be interesting spontaneous animal models to investigate new strategies of cancer immunotherapy in an immune-suppressed tumor microenvironment.

One‐year conditional survival of dogs and cats with invasive mammary carcinomas: A concept inspired from human breast cancer

“…With respect to immunophenotype, PR positivity of feline MCs was a protecting factor during the first 4 months of follow‐up, and at months 9 and 10, with higher CSS probabilities associated with PR+ MCs than ER+ PR− and ER− PR− MCs. This is in agreement with the favourable prognostic value of PR in feline MCs 37 . In dogs, luminal (ER+ and/or PR+) MCs showed a late increase in 1‐year CSS, from 76 ± 5% at month 5 to 92 ± 4% at month 12 (+16% gain in CSS in 7 months): the probability for a dog of dying from a luminal MC during the subsequent year became negligible if the dog had survived 1 year.…”

“…Immunohistochemistry (IHC) was performed using a Benchmark XT automated instrument (Ventana Medical Systems, Roche Diagnostics) as previously described, 8,21,22,24,37 and further detailed in Table S1. The antibodies used were p63 (used as myoepithelial marker), pancytokeratin (used as marker of metastatic epithelial cells in lymph nodes), LMO2 (lymphendothelial marker to better assess tumour emboli), ER (Oestrogen Receptor α), PR (Progesterone Receptor), HER2 (Human Epidermal growth factor Receptor 2), and Ki‐67 (proliferation marker).…”

Unfavorable Prognostic Effects of the Stem Cell Pluripotency Factor Sox2 in Feline Invasive Mammary Carcinomas

“…By multivariate survival analysis, mammary cancer progression (disease-free interval) in feline patients of the present study was independently modulated by Sox2, tumor size, ER and AR, with larger tumor size associated with poor prognosis, as frequently reported in FMCs (19)(20)(21)(49)(50)(51)(52)(53)(54)(55), AR associated with decreased probabilities of cancer progression (20), and ER expression associated with shortened DFI. This unfavorable effect of ER could seem paradoxical, as ERpositive breast cancers are associated with better outcomes than ER-negative breast cancers (56).…”

“…For the study of Sox2 expression in feline mammary carcinomas, a previously described cohort of 180 female cats was used. These cats diagnosed with invasive mammary carcinoma were treated solely by mastectomy (19)(20)(21). Owners signed an informed consent for approval of inclusion of their pet cats in the present study.…”

“…In this cohort, the immunohistochemical expression of ER, PR, HER2, Ki-67, EGFR, basal cytokeratins 5/6, basal cytokeratin 14, EGFR, AR, Bcl-2, FOXA1, and FoxP3 used as a regulatory T-cell marker has been previously described (19)(20)(21). For Sox2 immunohistochemistry, slides were heated at 95 • C for 1 h in a basic buffer (CC1 cell conditioning medium, Roche Diagnostics 950-124) to achieve heat-induced epitope retrieval.…”