Immune system and angiogenesis-related potential surrogate biomarkers of response to everolimus-based treatment in hormone receptor-positive breast cancer: an exploratory study

Purpose

mTOR inhibitor everolimus is used for hormone receptor-positive (HR+)/HER2-negative metastatic breast cancer (mBC). No reliable predictive biomarker of response is available. Following evidences from other solid tumors, we aimed to assess the association between treatment-associated immune system features and everolimus activity.

Methods

We retrospectively explored a correlation with the therapeutic activity of everolimus and tumor-associated immune pathways with ingenuity pathway analysis (IPA), neutrophil-to-lymphocyte ratio (NLR), circulating lymphocytes, and endothelial cells (CECs) in 3 different HR+ mBC studies, including the BALLET phase IIIb study.

Results

The circulating levels of CD3⁺/CD8⁺, CD3⁺/CD4⁺, and overall T lymphocytes were higher in responders versus non-responders at baseline (p = 0.017, p < 0.001, p = 0.034) and after treatment (p = 0.01, p = 0.003, p = 0.023). Reduced CECs, a tumor neoangiogenesis marker, were observed in responders after treatment (p < 0.001). Patients with low NLR (≤ 4.4) showed a better progression-free survival compared to patients with high NLR (> 4.4) (p = 0.01). IPA showed that the majority of immunity-related genes were found upregulated in responders compared to non-responders before treatment, but not after.

Conclusions

Lymphocytes subpopulations, CECs and NLR could be interesting biomarkers predictive of response to everolimus-based regimens, potentially useful in daily clinical practice to select/monitor everolimus-based treatment in mBC. Further studies to confirm such hypotheses are warranted.

Collagen ultrastructural symmetry and its malignant alterations in human breast cancer revealed by polarization-resolved second-harmonic generation microscopy

Several specific alterations of the extracellular matrix can be considered a distinctive hallmark of cancer. In particular, a different morphology of the collagen scaffold is frequently found within the peritumoural environment. In this study, we report about a significant difference in the ultrastructural organization of collagen at the supra-molecular level between the perilesional scaffold and the tumour area in human breast carcinoma samples. In particular, we demonstrated that polarization-resolved second-harmonic generation (P-SHG) microscopy is able to link the altered collagen architecture at the ultrastructural level found in perilesional tissue with a different organization of collagen fibrils at the molecular level.

Infiltrating Mast Cell-Mediated Stimulation of Estrogen Receptor Activity in Breast Cancer Cells Promotes the Luminal Phenotype

Tumor growth and development is determined by both cancer cell-autonomous and microenvironmental mechanisms, including the contribution of infiltrating immune cells. Because the role of mast cells (MC) in this process is poorly characterized and even controversial, we investigated their part in breast cancer. Crossing C57BL/6 MMTV-PyMT mice, which spontaneously develop mammary carcinomas, with MC-deficient C57BL/6-Kit^W-sh/W-sh (Wsh) mice, showed that MCs promote tumor growth and prevent the development of basal CK5-positive areas in favor of a luminal gene program. When cocultured with breast cancer cells in vitro, MCs hindered activation of cMET, a master regulator of the basal program, and simultaneously promoted expression and activation of estrogen receptor (ESR1/ER) and its target genes (PGR, KRT8/CK8, BCL2), which are all luminal markers. Moreover, MCs reduced ERBB2/HER2 levels, whose inhibition further increased ESR1 expression. In vivo and in silico analysis of patients with breast cancer revealed a direct correlation between MC density and ESR1 expression. In mice engrafted with HER2-positive breast cancer tumors, coinjection of MCs increased tumor engraftment and outgrowth, supporting the link between MCs and increased risk of relapse in patients with breast cancer. Together, our findings support the notion that MCs influence the phenotype of breast cancer cells by stimulating a luminal phenotype and ultimately modifying the outcome of the disease. SIGNIFICANCE: Mast cells impact breast cancer outcome by directly affecting the phenotype of tumor cells through stimulation of the estrogen receptor pathway.

Combined targeting of EGFR and HER2 against prostate cancer stem cells

Progression of prostate cancer has been associated with EGFR and HER2 activation and to tumor-initiating cells contribution toward chemotherapy resistance. We investigated the efficacy of a dual intervention against EGFR and HER2 to deplete the tumor-initiating cells, optimize the chemotherapy management and prevent the progression of castration-resistant prostate cancer (CRPC) cells. Using DU145, PC3, and 22Rv1 CRPC cell lines, biochemical analysis revealed activation of EGFR, HER2, MAPK, and STAT3 in DU145 and 22Rv1, and AKT and SRC in DU145 and PC-3. pSTAT3 nuclear staining was observed in DU145 xenografts and in 12 out of 14 CRPC specimens. The in vivo dual targeting of ErbB receptors with Cetuximab and Trastuzumab combined with chemotherapy caused an effective antitumor response in DU145 xenografted mice displaying STAT3 activation; conversely PC-3 bearing mice experienced tumor relapse. The potentiating of in vivo cytotoxic effect in DU145 model was accompanied by a significant decrease of prostatosphere-forming capacity assessed in vitro on residual tumor cells. Additionally, combined treatment in vitro with Cetuximab, Trastuzumab and chemotherapy negatively affected DU145 and 22Rv1 sphere formation, suggesting the critical function of ErbB receptors for tumor-initiating cells proliferation; no effect on PC-3 clonogenic potential was observed, indicating that other receptors than EGFR and HER2 may sustain PC3 tumor-initiating cells. These findings provided the preclinical evidence that the dual inhibition of EGFR and HER2 by targeting tumor-initiating cells may improve the efficacy of the current chemotherapy regimen, bringing benefits especially to castration-resistant patients with activated STAT3, and preventing disease progression.

Abstract P3-02-01: Fatty acid uptake as a potentially new resistance mechanism to anti-HER2 treatments in HER2-positive breast cancer

Background: Although anti-HER2 treatments, including the monoclonal antibodies trastuzumab (T) and pertuzumab (P) and the tyrosine kinase inhibitor lapatinib (L), have remarkably improved the prognosis of patients with HER2-positive breast cancer (HER2+ BC), acquired resistance to these compounds remains a major clinical issue. HER2-mediated signaling induces fatty acid (FA) de novo biosynthesis, and ongoing clinical trials are investigating FA synthase enzyme (FASN) inhibitors in combination with anti-HER2 treatments. We hypothesized that by inhibiting FA biosynthesis, HER2 inhibitors make HER2+ BC cells dependent on extracellular FA uptake, which could contribute to resistance to anti-HER2 treatments. Methods: In tumor biopsy specimens from HER2+ BC patients treated with preoperative T-containing chemotherapy (ChT), we performed quantitative real time PCR (qRT-PCR) to measure expression levels of the lipoprotein lipase (LPL) enzyme and the FA transporter CD36, two key players in the uptake of extracellular FAs. The same analyses were also performed in surgical tumor specimens from patients failing to achieve pathologic complete response (pCR), and paired Wilcoxon test was used to compare CD36 expression levels of pre- versus post-treatment tumors. In MDA-MB-361, HCC1954 and BT474 HER2+ BC cell lines, we investigated the association between baseline CD36 expression and cells’ sensitivity to L, or their ability to uptake the docosahexanoic acid (DHA) from culture media. Finally, we assessed the antiproliferative effect of combining L with the CD36 inhibitor Sulfo N-Succinimidoyl Oleate (SSO). Results: 82 patients with stage II-III HER2+ BC were treated with preoperative ChT plus T at Fondazione IRCCS Istituto Nazionale dei Tumori between January 2013 and December 2017. As expected, achieving pCR was associated with better relapse-free survival (RFS) and overall survival (OS). Baseline LPL and CD36 expression did not correlate with pCR probability (p=0.15 and 0.1, respectively), nor with RFS (p=0.28 and 0.7, respectively) or OS (p=0.42 and 0.35, respectively). On the other hand, in 20 patients failing to achieve pCR, we found significantly increased LPL (p=0.00096) and a trend towards increased CD36 (p=0.12) expression in post-treatment surgical specimens. In a parallel cohort of 17 stage II-III HER2+ BC patients enrolled in a prospective study, LPL and CD36 expression was significantly increased 21 days after the first administration of single-agent T (p=0.0002 and p&lt;0.0001, respectively). In keeping with our working hypothesis, cell susceptibility to L was inversely associated with CD36 expression or DHA uptake, with L-sensitive BT474 cells displaying the lowest CD36 expression and DHA uptake from culture media. Consistent with analyses on tumor specimens from patients, treatment with L increased CD36 gene expression and protein levels in L-resistant HCC1954 cells, but not in L-sensitive BT474 ones. Finally, SSO showed additive antiproliferative effects in combination with L in HCC1954, but not in BT474 cells. Conclusions: This is the first study to show that pharmacological inhibition of HER2 induces short- and long-term upregulation of LPL/CD36 expression in HER2+ BC cell lines and tumor specimens, and that CD36 inhibition sensitizes intrinsically resistant HER2+ BC cells to L. Prospective clinical studies are required to validate the role of enhanced FA uptake as a potential mechanism of resistance to anti-HER2 treatments in HER2+ BC.

Citation Format: Claudio Vernieri, Lorenzo Castagnoli, Francesca Ligorio, Antonino Belfiore, Elena Fasano, Paola A. Corsetto, Simona Faraci, Marta Brambilla, Francesca Corti, Tiziana Triulzi, Daniele Generali, Andrea Vingiani, Angela M. Rizzo, Giulia V. Bianchi, Giuseppe Capri, Elda Tagliabue, Filippo de Braud, Giancarlo Pruneri, Serenella M. Pupa. Fatty acid uptake as a potentially new resistance mechanism to anti-HER2 treatments in HER2-positive breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-02-01.

Abstract P4-10-32: Commensal gut microbiota influences efficacy of trastuzumab in patients with HER2-positive breast carcinoma

Although the clinical benefit of trastuzumab for the management of HER2-positive breast carcinomas (BCs) has been largely demonstrated, many women, even those reported to have tumors potentially most sensitive to trastuzumab (e.g., HER2-enriched by PAM50 and with infiltrating immune cells) do not respond to this agent. The relevance of immunity in the cytotoxic mechanism of action of trastuzumab supports the notion that the anti-tumor effect of this monoclonal antibody depends on host immune system activity. Since gut commensal bacteria reportedly contribute to the development and maintenance of the immune system and have immunomodulatory effects, we investigated whether a relationship between gut microbiota composition and the response to trastuzumab exists in patients with HER2-positive BC.

Stool samples were collected from 18 patients with primary HER2-positive BCs before the outset of neoadjuvant trastuzumab-based chemotherapy and analyzed by 16S rRNA gene profiling using Illumina Miseq platform. Gut microbiota β-diversity analysis by UniFrac algorithm revealed a heterogeneous microbiota composition mainly due to differences in the relative abundance of Bacteroides, Faecalibacterium and a genus belonging to Ruminococcaceae family. Unsupervised analysis identified two microbiota clusters that significantly discriminated patients according to pathological complete response (pCR) (p=0.0128, by Fisher test). No association between microbiota clusters and PAM50 molecular classification of tumor biopsies, as evaluated by gene expression, was observed. Moreover, HER2-enriched cases were distributed in the two microbiota clusters based on trastuzumab response. Differences in the intestinal microbiota between responsive (R) and non-responsive (NR) patients were assessed by LEfSe analysis: a significant higher and lower abundance of Clostridiales taxonomic order and Bacteroides taxonomic genus, respectively, was foundin R as compared to NR patients. Immune genes expressed in tumor biopsies that were found significantly correlated with these bacteria mainly belong to innate and adaptive immune response and cellular response to tumor necrosis factor pathways.

To investigate the causal role of gut microbiota in trastuzumab benefit, FVB mice bearing syngeneic mammary carcinoma overexpressing human HER2 were transplanted with fecal material from R and NR patients after intestinal flora depletion by the use of an antibiotic cocktail. The mouse response to trastuzumab treatment recapitulated the response observed in patients from which stool derived.

The obtained results support the contribution of gut microbiota in trastuzumab activity by influencing tumor immune microenvironment, independently of tumor intrinsic molecular characteristics. These data represent the proof-of-concept that manipulating gut microbes in resistant patients could be a new strategy to improve the response to trastuzumab.

Supported by AIRC

Citation Format: Elda Tagliabue, Martina Di Modica, Giorgio Gargari, Viola Regondi, Arianna Bonizzi, Stefania Arioli, Fabio Corsi, Simone Guglielmetti, Tiziana Triulzi. Commensal gut microbiota influences efficacy of trastuzumab in patients with HER2-positive breast carcinoma [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-10-32.

Extracellular Matrix Features Discriminate Aggressive HER2-Positive Breast Cancer Patients Who Benefit from Trastuzumab Treatment

We previously identified an extracellular matrix (ECM) gene expression pattern in breast cancer (BC), called ECM3, characterized by a high expression of genes encoding structural ECM proteins. Since ECM is reportedly implicated in response to therapy of BCs, the aim of this work is to investigate the prognostic and predictive value of ECM3 molecular classification in HER2-positive BCs. ECM3 resulted in a robust cluster that identified a subset of 25-37% of HER2-positive tumors with molecular aggressive features. ECM3 was significantly associated with worse prognosis in two datasets of HER2-positive BCs untreated with adjuvant therapy. Analyses carried out on two of our cohorts of patients treated or not with adjuvant trastuzumab showed association of ECM3 with worse prognosis only in patients not treated with trastuzumab. Moreover, investigating a dataset that includes gene profile data of tumors treated with neoadjuvant trastuzumab plus chemotherapy or chemotherapy alone, ECM3 was associated with increased pathological complete response if treated with trastuzumab. In the in vivo experiments, increased diffusion and trastuzumab activity were found in tumors derived from injection of HER2-positive cells with Matrigel that creates an ECM-rich tumor environment. Taken together, these results indicate that HER2-positive BCs classified as ECM3 have an aggressive phenotype but they are sensitive to trastuzumab treatment.

Modulation of Pulmonary Microbiota by Antibiotic or Probiotic Aerosol Therapy: A Strategy to Promote Immunosurveillance against Lung Metastases

Pulmonary immunological tolerance to inhaled particulates might create a permissive milieu for lung metastasis. Lung microbiota contribute to pulmonary tolerance; here, we explored whether its manipulation via antibiotic or probiotic aerosolization favors immune response against melanoma metastasis. In lungs of vancomycin/neomycin-aerosolized mice, a decrease in bacterial load was associated with reduced regulatory T cells and enhanced T cell and NK cell activation that paralleled a significant reduction of melanoma B16 lung metastases. Reduction of metastases also occurred in lungs transplanted with bacterial isolates from antibiotic-treated lungs. Aerosolized Lactobacillus rhamnosus strongly promoted immunity against B16 lung metastases as well. Furthermore, probiotics or antibiotics improved chemotherapy activity against advanced B16 metastases. Thus, we identify a role for lung microbiota in metastasis and show that its targeting via aerosolization is a therapy that can prevent metastases and enhance responses to chemotherapy.

Abstract 4959: The gut microbiota contributes to the effectiveness of HER2-targeted therapy

Recently, the composition of the gut microbiota, due to its influence on host immune system, has been linked to the effectiveness of chemotherapy and immunotherapy. Since trastuzumab, besides inhibiting the HER2 signaling, recruits innate and adaptive immune cells that mediate its cytotoxic activity in the tumor, we hypothesized that commensal bacteria can be a source of heterogeneity for the response to therapy in patients with HER2-positive breast cancer (HER2+BC).

The impact of the gut microbiota on anti-HER2 therapy was studied in mice with the intestinal flora alterated by the treatment with vancomycin or streptomycin-two broad spectrum antibiotics poorly absorbed in the intestine. The association between commensal bacteria composition and clinical efficacy of trastuzumab was investigated in a cohort of HER2+BC patients treated with neoadjuvant trastuzumab.

Administration of antibiotics impaired the efficacy of anti-HER2 monoclonal antibodies both in FVB and BALB/c mice bearing syngeneic mammary carcinomas expressing HER2. 16S rRNA gene profiling of FVB mouse feces showed that both antibiotics decreased bacterial α-diversity in the gut as evaluated by Chao1, Simpson and Shannon indices, lowering the abundance of Clostridiales bacteria. Mice transplanted with feces from antibiotic treated mice did not benefit from the anti-HER2 treatment supporting a direct relation between intestinal bacteria and therapeutic efficacy. Analysis by flow cytometry and immunohistochemistry of tumors grown in mice showed that alteration of gut microbiota compromised the recruitment of CD4+ T cells and Natural Killer (CD49b+, GZMB+) cells upon anti-HER2 administration. Fecal 16S rRNA gene sequencing demonstrated a significantly higher microbial α-diversity in patients who achieved a pathological complete response compared to non-responders using several indices. Moreover, a clustering effect by patient’s response was observed visualizing the β-diversity. OTUs belonging to the Clostridiales and Bacteroidales orders were reduced and enriched, respectively, in non-responders.

Our data support that the composition of the gut microbiota, especially as regards the abundance of Clostridiales bacteria, has a role in the therapeutic efficacy of trastuzumab both in mice and patients. Therefore, the manipulation of intestinal bacteria may represent a new strategy to improve the cure of HER2+BC patients.

(Supported by Associazione Italiana per la Ricerca sul Cancro).

Citation Format: Martina Di Modica, Viola Regondi, Giorgio Gargari, Arianna Bonizzi, Stefania Arioli, Beatrice Belmonte, Claudio Tripodo, Simone Guglielmetti, Fabio Corsi, Tiziana Triulzi, Elda Tagliabue. The gut microbiota contributes to the effectiveness of HER2-targeted therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4959.

Exploiting FAsting-mimicking Diet and MEtformin to Improve the Efficacy of Platinum-pemetrexed Chemotherapy in Advanced LKB1-inactivated Lung Adenocarcinoma: The FAME Trial

Advanced lung adenocarcinoma with inactive liver kinase B1 (LKB1) tumor suppressor protein is associated with poor response to immune checkpoint inhibitors and molecularly targeted agents, and with dismal patient prognosis. LKB1 is a central orchestrator of cancer cell metabolism, and halts tumor growth/proliferation during metabolic stress. Recent preclinical evidence suggests that LKB1-inactive lung adenocarcinoma is highly sensitive to metformin, a safe and low-cost antidiabetic compound that inhibits mitochondrial oxidative phosphorylation. The effects of metformin can be enhanced by nutrient deprivation (ie, glucose, amino acids), which reduces intracellular levels of ATP and anabolic precursors and can be achieved by the fasting mimicking diet (FMD). Noticeably, metformin also prevents resistance to cisplatin in preclinical in vitro and in vivo models of LKB1-inactive lung adenocarcinoma. Based on such preclinical evidence, the phase II FAME trial was designed to test the hypothesis that the addition of metformin, with or without cyclic FMD, to standard platinum-based chemotherapy improves the progression-free survival of patients with advanced, LKB-1 inactive lung adenocarcinoma. Enrolled patients will be randomized in a 1:1 ratio to receive cisplatin/carboplatin and pemetrexed with the addition of metformin alone (Arm A) or metformin plus FMD (Arm B). The FAME study will use a "pick-the-winner" design with the aim of establishing which of the 2 experimental treatments is superior in terms of antitumor efficacy and safety. The primary assumption of the study is that the combination of the 2 experimental treatments shall improve median progression-free survival from 7.6 months (historical data with chemotherapy alone) to 12 months. Secondary study endpoints are: objective response rate, overall survival, treatment tolerability, and compliance to the experimental treatment.

Early immune modulation by single-agent trastuzumab as a marker of trastuzumab benefit

BACKGROUND

Optimising the selection of HER2-targeted regimens by identifying subsets of HER2-positive breast cancer (BC) patients who need more or less therapy remains challenging. We analysed BC samples before and after treatment with 1 cycle of trastuzumab according to the response to trastuzumab.

METHODS

Gene expression profiles of pre- and post-treatment tumour samples from 17 HER2-positive BC patients were analysed on the Illumina platform. Tumour-associated immune pathways and blood counts were analysed with regard to the response to trastuzumab. HER2-positive murine models with differential responses to trastuzumab were used to reproduce and better characterise these data.

RESULTS

Patients who responded to single-agent trastuzumab had basal tumour biopsies that were enriched in immune pathways, particularly the MHC-II metagene. One cycle of trastuzumab modulated the expression levels of MHC-II genes, which increased in patients who had a complete response on treatment with trastuzumab and chemotherapy. Trastuzumab increased the MHC-II-positive cell population, primarily macrophages, only in the tumour microenvironment of responsive mice. In patients who benefited from complete trastuzumab therapy and in mice that harboured responsive tumours circulating neutrophil levels declined, but this cell subset rose in nonresponsive tumours.

CONCLUSIONS

Short treatment with trastuzumab induces local and systemic immunomodulation that is associated with clinical outcomes.

HER2 signaling regulates the tumor immune microenvironment and trastuzumab efficacy

Through whole-transcriptome profiling of HER2+ breast carcinomas (BCs), we previously showed that those sensitive to trastuzumab are addicted to this oncoprotein and are enriched in immune pathways, raising the hypothesis that HER2 itself regulates immune cell recruitment. In the present study we investigated the relationship between HER2 activity and the pro-trastuzumab tumor immune milieu. Gene expression profiling and immunohistochemistry analysis of 53 HER2+ BCs showed that trastuzumab-sensitive tumors expressed significantly higher levels of chemokines involved in immune cell recruitment, with higher infiltration of T cells and monocytes, and higher levels of PD-1 ligands than tumors that do not benefit from trastuzumab. In vitro analysis in HER2+ BC cells revealed that CCL2 production was induced by HER2 stimulation with EGF/HRG via the PI3K-NF-kB axis, and down-modulated by HER2 inhibition with trastuzumab. CCL2 expression was higher in HER2+/ER- than HER2+/ER+ BC cell lines, and degradation of ER by fulvestrant induced an enhancement in NF-κB transcriptional activity and consequent CCL2 expression. Trastuzumab efficacy relied on CCL2 levels and monocytes present in the tumor microenvironment in FVB mice bearing HER2+ mammary carcinoma cells. HER2 signals were also found to sustain the expression of PD-1 ligands in tumor cells via the MEK pathway. Overall, our results support the concept that the activated HER2 oncogene regulates recruitment and activation of tumor infiltrating immune cells and trastuzumab activity by inducing CCL2 and PD-1 ligands and that ER activity negatively controls the HER2-driven pro-trastuzumab tumor microenvironment.

Extracellular matrix proteins as diagnostic markers of breast carcinoma

Changes in amount and composition of extracellular matrix (ECM) are considered a hallmark of tumor development. We tested the hypothesis that abnormal production of ECM components leads to blood-released ECM molecules representing tumor circulating biomarkers. Candidate genes were selected through class comparison in two publicly available datasets and confirmed in paired normal and tumor associated fibroblasts from breast carcinoma (BC) specimens. Production and release of ECM molecules were evaluated in normal human dermal fibroblasts (NHDFs) treated with conditioned media from three BC cell lines. Plasma samples from healthy donors and from patients with malignant or benign breast disease were tested by ELISA for the presence of collagen 11a1 (COL11A1), collagen oligomeric matrix protein (COMP), and collagen 10a1 (COL10A1). Selected ECM molecules were investigated by IHC in malignant and benign specimens. In silico analysis of gene expression profiles identified 11 ECM genes significantly up-regulated in tumor versus normal tissue. Western blot analyses revealed increased levels of molecules encoded by three of these genes, COL11A1, COMP, and COL10A1, in cell lysates and supernatants of conditioned NHDFs. Class comparison and class prediction analyses of two independent series of human plasma samples identified the combination of COL11A1, COMP, and COL10A1 as potentially informative in discriminating BC patients from those with benign disease. The three molecules resulted expressed in the stroma of BC tissue samples. Our results indicate that circulating COL11A1, COMP, and COL10A1 may be useful in diagnostic assessment of suspicious breast nodules and ECM molecules could represent an avenue to biomarker identification.

Abstract P2-09-03: Identifying clinically relevant subgroups of women with HER2-positive breast cancer: An analysis of Neo-ALTTO using the 41-gene TRAR score

BACKGROUND: As a neoadjuvant regimen for HER2-positive early breast cancer (BC), the use of two HER2-directed agents is more effective in producing pathological complete (pCR) responses than trastuzumab alone. Nevertheless, highly effective dual anti-HER2 combination may be unnecessary in patients who already benefit from a single agent. We previously reported that our 41-gene TRAR score is an accurate predictor of response to trastuzumab, with low scores being predictive of response to trastuzumab and favorable prognosis (Triulzi T. et al., 2015).

PATIENTS AND METHODS: Tissue specimens from HER2-positive BC patients of Neo-ALTTO trial who received neoadjuvant trastuzumab and/or lapatinib plus paclitaxel were included in this study. Analysing RNA from fresh tissue using the 41-gene signature test, the area under the ROC curve (AUC) and the corresponding 95% confidence interval was computed to evaluate the predictive ability of TRAR score with respect to pCR, the primary endpoint of Neo-ALTTO. The prognostic role of TRAR score was investigated using a Cox regression model in univariate fashion. The patterns of Event Free Survival (EFS) according to the dichotomized TRAR score were estimated using the Kaplan–Meier method.

RESULTS: The TRAR score was assessed for 226 of the 455 (49.7%) patients enrolled in the Neo-ALTTO study: 136 (60%) presented with T2 tumors, 188 (83%) with N0/1 and 128 (56.6%) with estrogen receptor negative BC. In details, basal TRAR score was available for 69, 79 and 78 patients assigned to neoadjuvant trastuzumab, lapatinib, and their combination, respectively. Overall, patients achieving a pCR showed significantly lower levels of TRAR score than those with residual disease (p &lt;.0001). According to treatment arm, the classifier highly performed in discriminating responders (pCR) from non responders (no pCR) (trastuzumab: AUC = 0.74, 95% CI: 0.60–0.88; lapatinib: AUC = 0.76, 95% CI: 0.65–0.87; trastuzumab + lapatinib: AUC = 0.71, 95% CI: 0.59–0.83). Of note, the predictive value of the TRAR score was confirmed after adjustment for hormone receptor status. An AUC value of 0.70 (95% CI: 0.59–0.81) and 0.71 (95% CI: 0.62–0.80) was obtained in estrogen receptor positive and negative patients, respectively. We also evaluated the contribution to the predictive capability of TRAR levels and PAM50 by implementing a multivariate logistic regression model including both classifiers and clinically relevant variables. In this model the most predictive variable was TRAR. At a median follow-up of 7 years, with a total of 64 events, no statistically significant association was found between the TRAR score and EFS.

CONCLUSION: Overall, we show that our 41-gene signature is accurate in predicting patient response to neoadjuvant HER2 targeted therapy in terms of pCR. In particular, low levels of TRAR score can identify a HER2-positive breast cancer subgroup highly responsive to trastuzumab as monotherapy for whom combination with other HER2-targeted drugs does not appear justified and may be one tool used for exploring de-escalating strategies without sacrificing outcomes.

Citation Format: Di Cosimo S, Triulzi T, De Cecco L, Pizzamiglio S, de Azambuja E, Fumagalli D, Pusztai L, Harbeck N, Izquierdo M, de la Pena L, Huober J, Baselga J, Piccart M, Verderio P, Tagliabue E. Identifying clinically relevant subgroups of women with HER2-positive breast cancer: An analysis of Neo-ALTTO using the 41-gene TRAR score [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-09-03.

Abstract P4-21-33: HER2 activity regulates the pro-trastuzumab immune tumor microenvironment

It is well know that trastuzumab activity against HER2-positive breast carcinomas (BCs) depends also on immune cells. Our genomic analysis of 53 HER2-positive BCs indicated that those exquisitely sensitive to treatment are addicted to this oncoprotein and are enriched in immune pathways and T-cells infiltration, raising the hypothesis that HER2 regulates immune cells recruitment. The aim of this study was to investigate how HER2 activity contributes to mold tumor microenvironment.

Gene expression profile analysis of 53 HER2-pos BCs showed that trastuzumab-sensitive tumors express significantly higher levels of chemokines involved in immune cells recruitment (IFNγ-related CXCLs and CCLs) and higher levels of immune checkpoint ligands (PD-L1, PD-L2) than tumors that do not benefit from trastuzumab. Immunohistochemistry analysis on FFPE tumor specimens showed a significant positive association between tumor cell positivity for CXCL9, CXCL10 and CCL2 and trastuzumab sensitivity. In vitro analysis in HER2-positive BC cell lines revealed that while IFNγ-related chemokines (CXCL9 and CXCL10) are not directly regulated by HER2 signaling, CCL2 was significantly up-regulated both at mRNA and protein levels by HER2 stimulation with EGF/HRG and down-modulated by HER2 inhibition with trastuzumab. The EGF-induced increase in CCL2 expression was abrogated by the concomitant treatment with PI3K inhibitor but not with MEK inhibitor, indicating that HER2 regulates CCL2 expression via the PI3K pathway. HER2 signals derived from cell stimulation with EGF/HRG caused also the upmodulation of PD-L1/PD-L2 both at mRNA and protein levels while their inhibition with trastuzumab reduced their levels.

Overall, our results support the notion that the activated HER2 oncogene concomitantly induces the expression of CCL2 and PD-L1/PD-L2 regulating infiltration of pro-trastuzumab immune cells and their suppression. Thus, it is likely that activity of trastuzumab in therapy-responsive tumors derives from its ability in relieving suppression of recruited antitumor effector immunity.

Supported by Italian Association for Cancer Research (AIRC).

Citation Format: Tagliabue E, Forte L, Regondi V, Ghirelli C, Aiello P, Triulzi T. HER2 activity regulates the pro-trastuzumab immune tumor microenvironment [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-21-33.

Expression and prognostic significance of the autoimmune regulator gene in breast cancer cells

The autoimmune regulator gene (AIRE) plays a fundamental role in tolerance by promoting the expression of tissue-specific antigens in medullary thymic epithelial cells (mTECs). Recently, AIRE expression was detected also in human keratinocytes and in tumors originating in stratified epithelia. Here, we tested whether AIRE is expressed in cancer cells. We analyzed AIRE expression in cancer cases from The Cancer Genome Atlas (TCGA) RNA-seq dataset and we found association with better outcome. AIRE protein expression was verified by immunohistochemistry in a cohort of 39 human breast cancer specimens and its prognostic relevance was confirmed in microarray-based gene expression data set NKI-295 and KM-Plotter. Both in the RNA-seq and gene expression datasets analyzed, AIRE expression was an independent strong prognostic factor for relapse-free survival (RFS), particularly in estrogen receptor-positive tumors. Enrichment of translation-related pathways was observed in AIRE-expressing tumors by Ingenuity Pathway Analysis and a significant increase of cells in G1 phase and activation of caspase cascades was induced by AIRE transfection in breast cancer luminal cell lines, suggesting that AIRE-induced over-translation of proteins lead to cycle arrest and apoptosis. These data are the first to identify AIRE expression in breast cancer and an association with prognosis.

Taxanes enhance trastuzumab-mediated ADCC on tumor cells through NKG2D-mediated NK cell recognition

Recent clinical data indicate a synergistic therapeutic effect between trastuzumab and taxanes in neoadjuvantly treated HER2-positive breast cancer (BC) patients. In HER2+ BC experimental models and patients, we investigated whether this synergy depends on the ability of drug-induced stress to improve NK cell effectiveness and thus trastuzumab-mediated ADCC. HER2+ BC cell lines BT474 and MDAMB361 treated with docetaxel showed up-modulation of NK activator ligands both in vitro and in vivo, accompanied by a 15-40% increase in in vitro trastuzumab-mediated ADCC; antibodies blocking the NKG2D receptor significantly reduced this enhancement. NKG2D receptor expression was increased by docetaxel treatment in circulating and splenic NK cells from mice xenografted with tumor cells, an increase related to expansion of the CD11b+Ly6G+ cell population. Accordingly, NK cells derived from HER2+ BC patients after treatment with taxane-containing therapy expressed higher levels of NKG2D receptor than before treatment. Moreover, plasma obtained from these patients recapitulated the modulation of NKG2D on healthy donors' NK cells, improving their trastuzumab-mediated activity in vitro. This enhancement occurred mainly using plasma from patients with low NKG2D basal expression. Our results indicate that taxanes increase tumor susceptibility to ADCC by acting on tumor and NK cells, and suggest that taxanes concomitantly administered with trastuzumab could maximize the antibody effect, especially in patients with low basal immune effector cytotoxic activity.

Pathobiological implications of the d16HER2 splice variant for stemness and aggressiveness of HER2-positive breast cancer

We have previously shown that the d16HER2 splice variant is linked to HER2-positive breast cancer (BC) tumorigenesis, progression and response to Trastuzumab. However, the mechanisms by which d16HER2 contributes to HER2-driven aggressiveness and targeted therapy susceptibility remain uncertain. Here, we report that the d16HER2-positive mammary tumor cell lines MI6 and MI7, derived from spontaneous lesions of d16HER2 transgenic (tg) mice and resembling the aggressive features of primary lesions, are enriched in the expression of Wnt, Notch and epithelial–mesenchymal transition pathways related genes compared with full-length wild-type (WT) HER2-positive cells (WTHER2_1 and WTHER2_2) derived from spontaneous tumors arising in WTHER2 tg mice. MI6 cells exhibited increased resistance to anoikis and significantly higher mammosphere-forming efficiency (MFE) and self-renewal capability than the WTHER2-positive counterpart. Furthermore, d16HER2-positive tumor cells expressed a higher fraction of CD29^High/CD24⁺/SCA1^Low cells and displayed greater in vivo tumor engraftment in serial dilution conditions than WTHER2_1 cells. Accordingly, NOTCH inhibitors impaired mammosphere formation only in MI6 cells. A comparative analysis of stemness-related features driven by d16HER2 and WTHER2 in ad hoc engineered human BC cells (MCF7 and T47D) revealed a higher MFE and aldehyde dehydrogenase-positive staining in d16HER2- vs WTHER2-infected cells, sustaining consistent BC-initiating cell enrichment in the human setting. Moreover, marked CD44 expression was found in MCF7_d16 and T47D_d16 cells vs their WTHER2 and Mock counterparts. Clinically, BC cases from two distinct HER2-positive cohorts characterized by high levels of expression of the activated-d16HER2 metagene were significantly enriched in the Notch family and signal transducer genes vs those with low levels of the metagene.

Whole-transcriptome analysis links trastuzumab sensitivity of breast tumors to both HER2 dependence and immune cell infiltration

While results thus far demonstrate the clinical benefit of trastuzumab, some patients do not respond to this therapy. To identify a molecular predictor of trastuzumab benefit, we conducted whole-transcriptome analysis of primary HER2+ breast carcinomas obtained from patients treated with trastuzumab-containing therapies and correlated the molecular portrait with treatment benefit.

The estimated association between gene expression and relapse-free survival allowed development of a trastuzumab risk model (TRAR), with ERBB2 and ESR1 expression as core elements, able to identify patients with high and low risk of relapse. Application of the TRAR model to 24 HER2+ core biopsies from patients treated with neo-adjuvant trastuzumab indicated that it is predictive of trastuzumab response. Examination of TRAR in available whole-transcriptome datasets indicated that this model stratifies patients according to response to trastuzumab-based neo-adjuvant treatment but not to chemotherapy alone. Pathway analysis revealed that TRAR-low tumors expressed genes of the immune response, with higher numbers of CD8-positive cells detected immunohistochemically compared to TRAR-high tumors.

The TRAR model identifies tumors that benefit from trastuzumab-based treatment as those most enriched in CD8-positive immune infiltrating cells and with high ERBB2 and low ESR1 mRNA levels, indicating the requirement for both features in achieving trastuzumab response.

Abstract 3924: AIRE is expressed and associated with good prognosis in breast cancer

The transcription factor Autoimmune Regulator (AIRE) gene plays a fundamental role in tolerance process by promoting the ectopic expression of thousands of genes encoding for tissue-specific antigens (TSAs) in medullary thymic epithelial cells (mTECs). Beside the high expression of AIRE in mTECs, there are few evidences of AIRE expression in other lymphoid organs and very recently, AIRE was described to be expressed in human and mouse keratinocytes and in tumors originating in stratified and pseudostratified epithelia. Therefore, we evaluated the hypothesis that AIRE could be expressed by epithelial tumors and we focused on breast cancer, for which large public datasets are available.

Our analysis on the TCGA, the largest public breast cancer RNA-seq dataset, revealed that AIRE is expressed in 33% of the cases, and Aire protein expression was confirmed in 26% of 115 human primary breast cancer specimens by immunohistochemistry analysis. AIRE expression was revealed associated to a better relapse-free survival in the TCGA patients and also in two public gene expression microarray-based dataset developed on Agilent and Illumina platform (NKI-295 and KM-plotter). In all the datasets analyzed, AIRE expression resulted an independent strong prognostic factor for relapse-free survival, particularly in ER-positive tumors. Ingenuity Pathway Analysis (IPA) showed that AIRE-expressing tumors were enriched in translation-related pathways, accordingly with AIRE's described function in mTECs. Moreover, in breast cancer luminal cell lines MCF-7 and MDA-MB-361 transfected with AIRE-expressing vector, a significant increase of cell in G1 phase and activation of caspases cascade were observed, supporting the hypothesis that genotoxic stress, induced by AIRE-mediated proteins over-translation, leads to cycle arrest and apoptosis.

These data highlight for the first time AIRE expression in breast cancer and an association with a better prognosis was revealed. Imbalance of cellular homeostasis, caused by AIRE transcriptional function, is a new unusual mechanisms to trigger apoptosis in breast cancer cells.

Citation Format: Francesca Bianchi, Loris De Cecco, Tiziana Triulzi, Sandra Romero-Cordoba, Michele Sommariva, Chiara Storti, Piera Aiello, Elda Tagliabue, Andrea Balsari, Lucia Sfondrini. AIRE is expressed and associated with good prognosis in breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3924.

Abstract 3826: Phenethyl isothiocyanate hampers growth and progression of HER2-positive breast cancers

Background: Almost 90% of all breast cancers (BCs) express a splice variant of HER2 lacking exon 16 (d16HER2), which promotes the generation of stable and active d16HER2 homodimers on the tumor cell surface. Comparison of the tumorigenic potential of human d16HER2 and the full-length HER2 (WTHER2) in transgenic mice revealed a significantly shorter latency period and a higher incidence of tumors in the d16HER2 line, suggesting enrichment of this variant in HER2+ BC stem cells. Based on reports that cruciferous vegetable-derived compounds such as isothiocyanates (ITCs) mediate strong anti-tumorigenic effects on numerous oncotypes and target BC stem cells, we tested the effect of the phenethyl ITC (PEITC), alone or together with Trastuzumab (T), which reportedly targets HER2+ BC stem cells, on d16HER2-positive tumor growth and progression in transgenic mice.

Methods: The percentage of tumor cells expressing high levels of CD29 and CD24 and low levels of SCA-1 (CD29high/CD24+/SCA-1low) murine stem cell markers was evaluated by multiparametric flow cytometry in cell models derived from spontaneous d16HER2 and WTHER2 transgenic lesions. Mammosphere forming efficiency (MFE%) was calculated in d16HER2- and WTHER2-positive tumor cells. The therapeutic activity of PEITC, T and their combination was assessed in vitro based on their ability to decrease the MFE% and the expression of stem cell markers in d16HER2- vs. WTHER2-positive tumor cells, and in vivo in d16HER2 transgenic mice. Analyses by western blot, histology/immunohistochemistry and magnetic resonance spectroscopy (MRS) are ongoing to assess apoptosis, necrosis and metabolomic profiles of treated tumors vs. controls.

Results: d16HER2 tumor cells showed a significantly higher MFE% and higher expression of stem cell markers than did WTHER2 tumor cells. PEITC and T significantly reduced MFE% as compared to controls (p = 0.0342 and p = 0.0083, respectively), and their combination exerted significantly stronger inhibition than T (p = 0.001) or PEITC (p = 0.0003) alone only in d16HER2 cells. The percentage of tumor cells expressing CD29high/CD24+/SCA-1low in d16HER2 tumor cells after treatment with T, PEITC or both was also reduced. Whereas PEITC monotherapy did not significantly reduce mammary tumor incidence compared to controls, while T effectively suppressed d16HER2-driven tumor growth (p = 0.0002), the combination of PEITC and T significantly heightened the impairment of mammary lesion development compared to T alone (p = 0.0046). Ex vivo metabolomic analyses by MRS of d16HER2-positive murine and human BC cell lines showed an increase in glycolytic pathway as compared to the respective WTHER2 cells.

Conclusions: Our results provide in vivo evidence that the combination of T and PEITC mediates a significantly greater anti-tumor effect than either alone, most likely targeting BC stem cells.

Supported by the Italian Ministry of Health and AIRC.

Citation Format: Ada Koschorke, Lorenzo Castagnoli, Gaia C. Ghedini, Tiziana Triulzi, Claudia Chiodoni, Rossella Canese, Egidio Iorio, Manuela Iezzi, Patrizia Nanni, Elda Tagliabue, Serenella M. Pupa. Phenethyl isothiocyanate hampers growth and progression of HER2-positive breast cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3826.

Abstract 748: Targeting the crosstalk between tumor cells and adipocytes to block breast cancer progression

It is now well-established that the local microenvironment of an emerging tumor plays a vital role in various steps of tumorigenesis. Stromal cells, such as fibroblasts, endothelial and various inflammatory cells, can contribute to tumor progression, and tumor cells can directly model their microenvironment, influencing host cells to secrete factors that favor cancer cell survival and growth. Recent studies have demonstrated the existence of cross-talk between breast cancer (BC) cells and adipocytes, the most abundant stromal cell in the breast, supporting their involvement in BC and consistent with epidemiological studies reporting the association of obesity and insulin resistance/diabetes with a higher risk and poor prognosis of BC.

Based on this evidence, we investigated whether adipocyte de-differentiation is the crucial trigger in inducing pro-tumor microenvironment remodeling and tumor progression.

Co-culture of 4T1 mouse mammary tumor cells using Transwell or their conditioned medium with mature adipocytes derived from the 3T3-L1 mouse cells induced adipocyte de-differentiation, observed as a reduced expression of specific differentiation markers (peripilin, adipocyte protein 2 (aP2), PPARã and adiponectin) in Western blots and by qRT-PCR, and a reduced triglyceride content as assessed by oil red O staining compared to mature adipocytes. Strong adipocyte de-differentiation, associated with an increase in pro-inflammatory molecules (IL6 and CCL2), was also induced in vitro by tumor interstitial fluids obtained from MMT-PyMT transgenic mice, but not by plasma of these mice. Preliminary studies to identify molecules involved in the cross-talk indicated that the phenomenon is exosome-unrelated.

Based on the relevant role of the PPARã transcription factor in inducing and maintaining adipocyte differentiation, we co-cultured adipocytes with 4T1 BC cells in the presence of several PPARã agonists enriched in the diets of many populations displaying a low incidence of cancer (þ3-fatty acids), and in the presence of glitazones (rosiglitazone and pioglitazone) to force adipocyte stable differentiation. While most of these compounds did not block adipocyte de-differentiation induced by tumor cells, pioglitazone and eicosanoid acid showed some activity in inhibiting this de-differentiation in vitro. Treatment of MMTV-PyMT transgenic mice at tumor onset by oral gavage with pioglitazone did not significantly reduce mammary tumor growth compared to controls, whereas eicosanoid acid treatment significantly reduced tumor multiplicity and tumor burden compared to controls.

Overall, our results suggest that tumor-induced adipocyte de-differentiation participates in tumorigenesis and that the blockade of this program can inhibit tumor progression.

Supported by AIRC and Fondazione Cariplo.

Citation Format: Tiziana Triulzi, Valentina Ciravolo, Viola Regondi, Martina Di Modica, Claudia Chiodoni, Elda Tagliabue. Targeting the crosstalk between tumor cells and adipocytes to block breast cancer progression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 748.