Triple-negative breast cancer (TNBC) patients do not benefit from target-specific treatments and is associated with a high relapse rate. Epidermal growth factor receptor is frequently expressed in TNBC and is a candidate for new therapies. In this work, we studied Cetuximab-mediated immune activity by NK cells. Thirteen activating/inhibitory receptors were examined on peripheral blood and tumor infiltrating NK cells. NK-cell functionality was evaluated using as effectors tumor-modulated NK cells and NK cells from patients. We evaluated the treatment with Cetuximab plus IL-2 or IL-15 in vivo in TNBC xenografts. Tumor NK-cells receptor profile showed upregulation of inhibitory receptors and downregulation of activating ones. Tumor-modulated NK cells were less cytotoxic. They could perform antibody-dependent cellular cytotoxicity (ADCC) triggered by Cetuximab, although impaired, it could still be restored by stimulation with IL-2 or IL-15. Patients with advanced disease displayed diminished levels of ADCC compared to healthy volunteers. ADCC was restored and potentiated with both cytokines, which were also effective in enhancing the therapeutic activity of Cetuximab in vivo. The combination of Cetuximab with IL-15 and IL-2 may be considered an attractive therapeutic approach to enhance the clinical efficacy of Cetuximab in TNBC.

PURPOSE Multiple studies have reported that breast cancer in young patients is associated with aggressive characteristics, and it is suggested that prognosis is worse independently of pathologic variables. PATIENTS AND METHODS We performed a retrospective analysis of the Breast Cancer Registry of the Argentinian Society of Mastology, including public and private centers. Patients ≤ 40 years of age at diagnosis were classified as “young,” and patients ≤ 35 years of age at diagnosis were classified as “very young.” Univariate and multivariate analyses were performed to detect differences between groups. RESULTS Patients ≤ 40 years of age comprised 10.40% (739/7,105) of the participants, with an average age of 35.61 ± 4.04 years. Multivariate analysis showed that human epidermal growth factor receptor 2 (HER2)-positive tumor phenotype (odds ratio [OR], 1.82), nodal involvement (OR, 1.69), histologic grade (grade 3 OR, 1.41), and tumor size (T2 OR, 1.37; T3-T4, 1.47) were independently associated with younger age at diagnosis. Patients ≤ 35 years of age (n = 286), compared with patients 36 to 40 years of age, had a higher proportion of HER2 tumors (24.58% v 16.94%; P = .021), absence of progesterone receptor expression (29.85% v 22.95%; P = .043), and stage 3 cancer (29.34% v 18.52%; P < .001). Fewer breast-conserving surgeries (75.37% v 62.89%; P < .001) and more adjuvant chemotherapy (59.04% v 36.66%; P < 0.001) were reported in patients ≤ 40 years of age. CONCLUSION In the population studied, breast cancer in young women was associated with aggressive pathologic features and locally advanced disease at the time of diagnosis. Moreover, tumor characteristics in very young patients with breast cancer nested in the population ≤ 40 years of age showed differences in important prognostic factors. More high-quality evidence is needed to improve treatment strategies in these patients.

Clinical studies suggest that triple negative breast cancer (TNBC) patients with epidermal growth factor receptor (EGFR)-expressing tumors could benefit from therapy withCetuximab, which targets EGFR. NK cells are the primary effectors of antibody (Ab)-dependent cell-mediated cytotoxicity (ADCC) and thus play a role in Ab-based therapies. We have previously described diminished levels of Cetuximab-mediated ADCC in vitro in patients with advanced breast cancer. Here, we investigated the potential causes of this NK-cell functional deficiency. We characterized NK-cell activating/inhibitory receptors in the peripheral blood of breast cancer patients and found CD85j inhibitory receptor overexpression. The capacity of NK cells to perform Cetuximab-triggered ADCC against TNBC cells correlated inversely with CD85j expression, even in the presence of the stimulatory cytokines IL-2 or IL-15. Hence, patients expressing high levels of CD85j had an impaired ability to lyse TNBC cells in the presence of Cetuximab. We also found that CD85j overexpression was associated with HLA-I and soluble HLA-G expression by tumors. A CD85j functional blockade with a CD85j antagonist Ab restored ADCC levels in breast cancer patients and reverted this negative effect. Our data suggest that strategies that overcome the hurdles of immune activation could improve Cetuximab clinical efficacy.Keywords: ADCC r CD85j r Cetuximab r EGFR r NK cells r Triple negative breast cancer Additional supporting information may be found in the online version of this article at the publisher's web-site Introduction NK cells are a major component of the innate immune system and can limit the growth and dissemination of several types of Correspondence: Dr. Estrella M. Levy e-mail: estrellamlevy@yahoo.com.ar tumors [1]. In cancer immune surveillance, NK cells can exert direct cellular cytotoxicity on tumor cells without prior sensitization and secrete immunostimulatory cytokines such as IFN-γ, which can control both local tumor growth and metastasis [2,3]. Moreover, NK cells act as effectors in Ab-dependent cell-mediated cytotoxicity (ADCC) [4]. Accordingly, it has been determined that NK-cell activity can play a significant role [13]. LIR-1, the most broadly expressed LIR family member, is an inhibitory receptor that binds multiple MHC-I molecules, both classical (HLA-A, -B, and -C) and nonclassical (HLA-E, -F, and -G) [12][13][14][15][16]. The inhibitory receptor LIR-1 (also known as ILT-2 and CD85j) is the only LIR expressed on NK cells [17]. Upon ligand binding, CD85j is able to inhibit NK-cell cytotoxicity [16,[18][19][20], as well as IFN-γ production [21]. Despite the fact that NK-cell inhibitory receptor engagement with target cells is considered a primary event in the formation of the inhibitory synapse and the subsequent prevention of cell lysis [22], CD85j receptor involvement in cancer has been poorly addressed. In lung cancer, CD85j expression was drastically reduced on intratumoral NK cells compared to blood NK cells [23]. In contrast, CD85j was upreg...

PURPOSE In recent years, unprecedented benefits have been observed with the development of cyclin-dependent kinase (CDK) 4 and 6 inhibitors for the treatment of hormone receptor–positive/human epidermal growth factor receptor 2–negative metastatic breast cancer. However, there is scarce evidence of their value in specific populations, such as patients carrying germline pathogenic variants in DNA repair–related genes. PATIENTS AND METHODS We retrospectively studied the efficacy of CDK 4/6 inhibitors plus endocrine therapy in patients with hormone receptor–positive/human epidermal growth factor receptor 2–negative advanced breast cancer. Three cohorts were compared, including patients harboring germline pathogenic variants in DNA repair–related genes (g BRCA1/2- ATM- CHEK2 mutated), those tested without these mutations (wild type [WT]), and the nontested subgroup. Relevant prognostic factors including age, metastatic site (visceral v nonvisceral), Eastern Cooperative Oncology Group, and prior treatment with CDK 4/6 inhibitors were stratified by univariate and multivariate Cox regression models. RESULTS Among the total population (n = 217), 15 (6.9%) patients carried g BRCA1/2 (n = 10)- ATM (n = 4)- CHEK2 (n = 1) pathogenic variants, 45 (20.7%) were WT, and 157 (72.4%) were nontested. Gene pathogenic variant carriers were younger ( P < .001). Most patients (164, 75.6%) had not received prior endocrine therapy in the advanced setting. Median progression-free survival was shorter in patients with evaluated germline pathogenic variants (10.2 months [95% CI, 5.7 to 14.7]), compared with WT and nontested patients (15.6 months [95% CI, 7.8 to 23.4], and (17.6 months [95% CI, 12.9 to 22.2]; P = .002). Consistently, a worse median overall survival was observed in the subgroup with germline pathogenic variants than in the WT group ( P = .006). Multivariable analysis showed that mutation status was an independent prognostic factor of progression-free survival ( P = .020) and overall survival ( P = .012). CONCLUSION In this retrospective real-world study, g BRCA1/ 2- ATM-CHEK2 pathogenic variants were independently associated with poor outcomes in patients with advanced breast cancer treated with CDK4/6 inhibitors.

1056 Background: HER2-low expression, defined as HER2 immunohistochemistry (IHC) score of 1+ or 2+ with negative in situ hybridization assay (FISH), accounts for 50% of breast cancers. There is limited and conflicting evidence regarding the efficacy of cyclin-dependent kinase (CDK) 4 and 6 inhibitors in patients with ER+ and HER2-low tumors. This study aimed to investigate the prognostic value of HER2-low expression in patients with ER+/HER2-negative advanced breast cancer treated with CDK 4/6 inhibitors. Methods: We retrospectively selected consecutive patients with ER+/HER2-negative advanced breast cancer treated with CDK 4/6 inhibitors plus endocrine therapy in our institution from May 2015 to Feb 2020. Two cohorts were compared, including HER2-0 (IHC score) and HER2-low (HER2 IHC score 1+ and 2+ [negative FISH]) tumors. Comparisons in progression-free survival (PFS) and overall survival (OS) were performed using a log-rank test. The prognostic value of HER2-low was investigated by the Cox regression model. Results: Among the 186 patients included, median age at treatment was 55 (r 27-84), and majority had ECOG 0 (126, 67.8%). Progesterone receptor was positive in 155 (83.3%) tumors. Of note, most patients received CDK4/6 inhibitors and endocrine therapy as first-line setting (131, 70.4%). Mostly received palbociclib (161, 86.6%), while ribociclib and abemaciclib were used in 23 (12.4%) and 2 (1.08%) patients, respectively. Overall, 27 patients (14.5%) had de novo metastatic disease, 68 (36.6%) had only bone metastases, and 69 (37.1%) had visceral disease. Of the total population, 64 (34.4%) tumors were HER2-low (43 [23.1%] HER2-1+, and 21 [11.3%] HER2-2+), and 122 (65.6%) were HER2-0. Median PFS among patients with HER2-0 and HER-low were 19 mo. (95% CI, 13.9-24.1), and 15.6 mo. (95% CI, 11.1-20.0), p = 0.074, respectively. In patients treated with CDK 4/6 in the first-line setting, no statistically significant differences were observed in terms of PFS and OS between HER2-0 and HER2-low (PFS HR 0.73 [95% CI, 0.47-1.13; p = 0.160], and OS HR 1.04 [95% CI, 0.51-2.14; p = 0.909]). Conclusions: In our study, HER2-low expression did not show a statistically significant impact on patients with ER+/HER2-negative advanced breast cancer treated with CDK 4/6 inhibitors. Our study supports the necessity of real-world evidence and the design of pooled analysis to understand the real implication of this biomarker in patients with ER+/HER2-negative tumors.