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Background: The optimal treatment approach for hormone receptor-positive/HER2-negative metastatic breast cancer (HR+/HER2-negative MBC) with aggressive characteristics remains controversial, with lack of randomized trials comparing cyclin-dependent kinase (CDK)4/6-inhibitors (CDK4/6i) + endocrine therapy (ET) with chemotherapy + ET., Materials and Methods: We conducted an open-label randomized phase II trial (NCT03227328) to investigate whether chemotherapy + ET is superior to CDK4/6i + ET for HR+/HER2-negative MBC with aggressive features. PAM50 intrinsic subtypes (IS), immunological features, and gene expression were assessed on baseline samples., Results: Among 49 randomized patients (median follow-up: 35.2 months), median progression-free survival (mPFS) with chemotherapy + ET (11.2 months, 95% confidence interval [CI]: 7.7-15.4) was numerically shorter than mPFS (19.9 months, 95% CI: 9.0-30.6) with CDK4/6i + ET (hazard ratio: 1.41, 95% CI: 0.75-2.64). Basal-like tumors under CDK4/6i + ET exhibited worse PFS (mPFS: 11.4 months, 95% CI: 3.00-not reached [NR]) and overall survival (OS; mOS: 18.8 months, 95% CI: 18.8-NR) compared to other subtypes (mPFS: 20.7 months, 95% CI: 9.00-33.4; mOS: NR, 95% CI: 24.4-NR). In the chemotherapy arm, luminal A tumors showed poorer PFS (mPFS: 5.1 months, 95% CI: 2.7-NR) than other IS (mPFS: 13.2 months, 95% CI: 10.6-28.1). Genes/pathways involved in BC cell survival and proliferation were associated with worse outcomes, as opposite to most immune-related genes/signatures, especially in the CDK4/6i arm. CD24 was the only gene significantly associated with worse PFS in both arms. Tertiary lymphoid structures and higher tumor-infiltrating lymphocytes also showed favorable survival trends in the CDK4/6i arm., Conclusions: The KENDO trial, although closed prematurely, adds further evidence supporting CDK4/6i + ET use in aggressive HR+/HER2-negative MBC instead of chemotherapy. PAM50 IS, genomic, and immunological features are promising biomarkers to personalize therapeutic choices., (© The Author(s) 2024. Published by Oxford University Press.)

Background: KRISTINE is an open-label, phase III study of trastuzumab emtansine + pertuzumab (T-DM1 + P) versus docetaxel + carboplatin + trastuzumab + pertuzumab (TCH + P) in patients with HER2-positive, stage II-III breast cancer. We investigated the association of biomarkers with clinical outcomes in KRISTINE., Methods: Patients were randomized to receive neoadjuvant T-DM1 + P or TCH + P and assessed for pathologic complete response (pCR; ypT0/is, ypN0). HER2 status (per central assessment), hormone receptor status, PIK3CA mutation status, HER2/HER3 mRNA levels, tumor-infiltrating lymphocyte levels, PD-L1 status, and NanoString data were analyzed. pCR rates by treatment arm were compared across biomarker subgroups. Analyses were descriptive., Results: Biomarker analyses included data from all 444 patients (T-DM1 + P, n = 223; TCH + P, n = 221) enrolled in KRISTINE. Biomarker distribution was balanced across treatment arms. All subgroups with higher HER2 amplification/expression and immune marker levels showed numerically higher pCR rates in both arms. Mutated versus non-mutated PIK3CA tumors were associated with numerically lower pCR rates in the T-DM1 + P arm but not in the TCH + P arm. In a multivariate analysis, Prediction Analysis of Microarray with the 50-gene classifier (PAM50) HER2-enriched subtype, HER2 gene ratio ≥ 4, and PD-L1-positive status positively influenced the pCR rate. Biomarkers associated with lower pCR rates (e.g., low HER2 levels, positive hormone receptor status, mutated PIK3CA) were more likely to co-occur. Dynamic on-treatment biomarker changes were observed. Differences in the treatment effects for T-DM1 + P versus TCH + P were similar to those observed in the intent-to-treat population for the majority of the biomarker subgroups., Conclusions: Although our biomarker analysis did not identify a subgroup of patients that benefited from neoadjuvant T-DM1 + P versus TCH + P, the data revealed that patients with higher HER2 amplification/expression and immune marker levels had improved response irrespective of treatment arm. These analyses confirm the role of HER2 tumor biology and the immune microenvironment in influencing pCR in the neoadjuvant setting and reaffirm the molecular diversity of HER2-positive breast cancer., Trial Registration: ClinicalTrials.gov NCT02131064. Registered 06 May 2014., (© 2023. The Author(s).)

Aim: The Cher-LOB randomised phase II study showed that the combination of lapatinib-trastuzumab plus chemotherapy increases pathologic complete response (pCR) rate compared with chemotherapy plus either trastuzumab or lapatinib. Here, we report the post hoc survival analysis as per treatment arm, pCR and biomarkers., Methods: The Cher-LOB study randomised 121 patients with human epidermal growth factor receptor 2-positive, stage II-IIIA breast cancer. A specific protocol to collect recurrence-free survival (RFS) and overall survival (OS) data was designed. Tumour-infiltrating lymphocytes (TILs) and PAM50-intrinsic subtyping were evaluated at baseline., Results: At 9-year median follow-up, a trend towards RFS improvement with lapatinib-trastuzumab over trastuzumab was observed (hazard ratio [HR] 0.44, 95% confidence interval [CI] 0.18-1.05). Combining treatment arms, pCR was significantly associated with both RFS (HR 0.12, 95% CI 0.03-0.49) and OS (HR 0.12, 95% CI 0.03-0.49). TILs were significantly associated with RFS (HR = 0.978 for each 1% increment). Luminal-A subtype was a significant and independent predictor of improved RFS as compared with other PAM50-based intrinsic subtypes at the multivariate analysis including the most relevant clinicopathologic variables (HR 0.29, 95% CI 0.09-0.94, p = 0.040)., Conclusions: Cher-LOB trial survival analysis confirmed the prognostic role of pCR and TILs and showed a signal for a better outcome with lapatinib-trastuzumab over trastuzumab., Trial Registration: NCT00429299., Competing Interests: Conflict of interest statement V.G. reports personal fees from Roche, Novartis, Eli Lilly and MSD outside the submitted work. D.G.G. reports personal fees from Roche, Novartis, Eli Lilly and Pierre Fabre, all outside the submitted work. A.F. reports personal fees from Roche, Novartis, Pfizer, Lilly, Daiichi and Seagen, all outside the submitted work. L.G. reports honoraria for lectures and ad boards from Lilly, Pfizer, Novartis and AstraZeneca, all outside the submitted work, reports travel accommodation and expenses from Novartis and Daiichi Sankyo and is an uncompensated member of the Olympia steering committee. A.M. reports grants and personal fees from Roche and Eisai; personal fees from Lilly, MacroGenics and Novartis and grants from Pfizer, all outside the submitted work. S.C. reports personal fees from Lilly Oncology outside the submitted work. A.P. reports grants and personal fees from Roche, AstraZeneca, Daiichi Sankyo, Merck Sharp & Dohme (MSD), PUMA Biotechnology, Novartis and Nanostring Technologies, personal fees from Seattle Genetics, Lilly, Pfizer, Guardant Health, Oncolytics Biotech and Abbvie, all outside the submitted work, and a patent (WO2018/103834A1) licensed to Nanostring Technologies, a patent (WO/2018/096191) issued. M.V.D. reports personal fees from Lilly, Genomic Health, Novartis and Celgene, all outside the submitted work. P.F.C. reports personal fees from Novartis, Eli Lilly, AstraZeneca, Tesaro, BMS and Roche, all outside the submitted work. All remaining authors have declared no conflicts of interest., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with unmet medical needs. Several studies have proved that high levels of tumor infiltrating lymphocytes (TILs) at diagnosis of TNBC confer better prognosis and patients respond better to specific chemotherapies. Nonetheless, current evidence suggests that only 15% of TNBC patients have very high levels of TILs, and another 15% lacks TILs. One possible reason to explain why patients have low TILs at diagnosis is that lymphocytes might be deactivated by an immune checkpoint in local lymph nodes, provoking their retention in there as they are unresponsive to other immune stimuli. We have identified 15 high TILs (≥50%) and 20 low TILs (≤5%) TNBC patients with localised tumour (T1c-T2N0M0) and compared the protein expression of five immune checkpoints in lymph nodes. We have also performed a customised 50-immune gene NanoString expression panel, the NanoString 360 Breast Cancer panel, and whole exome sequencing for mutation and neoantigen load analyses. In low TILs, we observed higher expression of CTLA-4 in local lymph nodes, which could explain why lymphocytes get retained in there and do not migrate to tumour. These patients have also higher neoantigen load and higher expression of B7.H3 and B7.H4 in the tumour. In high TILs, we observed more PD-L1+ tumour cells and more expanded humoral response. These results could provide a strategy to revert low tumour immune infiltration at diagnosis of TNBC, improving their prognosis., Competing Interests: Conflict of interest statement The authors declare the following financial interests/personal relationships, which may be considered as potential competing interests: A.Q. received transportation and accommodation fees from MSD outside the submitted work. V.P. has received fees as consultant, participated in advisory boards or received travel grants from Sysmex, Roche, MSD, AstraZeneca and Genomic Health. A.P. has received personal fees from Roche, Pfizer, Novartis, Amgen, BMS, Nanostring Technologies and Daiichi Sankyo; fees as a consultant from Roche, Pfizer, Novartis, Amgen, BMS, Puma, Oncolytics Biotech, MSD and Lilly; grants from Boehringer, Novartis, Roche, Nanostring, Sysmex Europa GmbH, MedSIR, Celgene, Astellas and Pzifer; is a member of the executive board of Reveal Genomics, SL, Beast International Group (BIG) and SOLTI cooperative group; and in the patronage committee of SOLTI Foundation and Actitud Frente al Cáncer Foundation. R.D. has declared advisory role for Roche, Boehringer Ingelheim, has received a speaker's fee from Roche, Ipsen, Amgen, Servier, Sanofi, Merck Sharp & Dohme, and research grants from Merck and Pierre Fabre. P.S. has received personal fees and fees as a consultant from AstraZeneca, Bayer, Boehringer Ingelheim, Merck, Novartis, Pfizer, Puma and Roche; grants from Astellas, AstraZeneca, Genentech, Novartis, Oncogenex and Roche. C.G. reports grants from Roche and Pfizer; and received personal fees from Daichii Sankyo, MSD, Astra Zeneca, outside the submitted work. J.P-G. has received fees as a consultant from Roche and Eli Lilly; and travel and accommodation expenses from Roche. E.M-C. has received travel and accommodation fees from BMS and MSD; personal fees and fees as a consultant from Novartis, Roche, BMS, MSD, Pier Fabre and Sanofi. L.M-A. has received consultancy from Roche; received an educational grant and travel from BMS; holds a research collaboration with NanoString Technologies; and received grants to the Institution from Grifols, Gilead, MSD, Jansen and AbbVie. J.C. has received fees as a consultant from Roche, Celgene, Cellestia, AstraZeneca, Biothera Pharmaceutical, Merus, Seattle Genetics, Daiichi Sankyo, Erytech, Athenex, Polyphor, Lilly, Servier, MSD, GSK, Leuko; personal fees from Roche, Novartis, Celgene, Eisai, Pfizer, Samsung Bioepis, Lilly, MSD, Daiichi Sankyo; research funding from Roche, Ariad pharmaceuticals, AstraZeneca, Baxalta GMBH/Servier Affaires, Bayer healthcare, Eisai, F. Hoffman-La Roche, Guardanth health, MSD, Pfizer, Piqur Therapeutics, Puma C, Queen Mary University of London, Seagen; and owns stock, patents and intellectual property from MedSIR. T.M., G.V., L.P., P.G., M.M., J.B.-H., C.A. and M.V. declare no competing interests., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Purpose: The prognostic and predictive value of intrinsic subtypes in hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer treated with endocrine therapy and ribociclib (RIB) is currently unknown. We evaluated the association of intrinsic subtypes with progression-free survival (PFS) in the MONALEESA trials., Methods: A retrospective and exploratory PAM50-based analysis of tumor samples from the phase III MONALEESA-2, MONALEESA-3, and MONALEESA-7 trials was undertaken. The prognostic relationship of PAM50-based subtypes with PFS and risk of disease progression by subtype and treatment were evaluated using a multivariable Cox proportional hazards model, adjusting for age, prior chemotherapy, performance status, visceral disease, bone-only metastases, histological grade, number of metastatic sites, prior endocrine therapy, and de novo metastatic disease., Results: Overall, 1,160 tumors from the RIB (n = 672) and placebo (n = 488) cohorts were robustly profiled. Subtype distribution was luminal A (LumA), 46.7%; luminal B (LumB), 24.0%; normal-like, 14.0%; HER2-enriched (HER2E), 12.7%; and basal-like, 2.6% and was generally consistent across treatment arms and trials. The associations between subtypes and PFS were statistically significant in both arms ( P < .001). The risks of disease progression for LumB, HER2E, and basal-like subtypes were 1.44, 2.31, and 3.96 times higher compared with those for LumA, respectively. All subtypes except basal-like demonstrated significant PFS benefit with RIB. HER2E (hazard ratio [HR], 0.39; P < .0001), LumB (HR, 0.52; P < .0001), LumA (HR, 0.63; P = .0007), and normal-like (HR, 0.47; P = .0005) subtypes derived benefit from RIB. Patients with basal-like subtype (n = 30) did not derive benefit from RIB (HR, 1.15; P = .77)., Conclusion: In this retrospective exploratory analysis of hormone receptor-positive and human epidermal growth factor receptor 2-negative advanced breast cancer, each intrinsic subtype exhibited a consistent PFS benefit with RIB, except for basal-like., Competing Interests: Aleix PratHonoraria: Nanostring Technologies, Bristol Myers Squibb, Novartis, Merck Sharp & Dohme, Pfizer, Roche, Lilly, Oncolytics Biotech, Amgen, Daiichi Sankyo, PUMA, Boehringer Anwesha ChaudhuryEmployment: Novartis Nadia SolovieffEmployment: NovartisStock and Other Ownership Interests: Novartis Nuria ChicTravel, Accommodations, Expenses: Novartis Agnes LteifEmployment: NovartisStock and Other Ownership Interests: Novartis Tetiana TaranEmployment: NovartisStock and Other Ownership Interests: Novartis Naveen BabbarEmployment: NovartisStock and Other Ownership Interests: Novartis Fei SuEmployment: NovartisStock and Other Ownership Interests: NovartisNo other potential conflicts of interest were reported.

Purpose: Predicting prognosis in HR + /HER2 - metastatic breast cancer (MBC) might be clinically useful; however, no validated prognostic biomarkers exist in this setting to date., Patients and Methods: In phase III, EGF30008 trial, 484 patients with HER2 - MBC who received letrozole and placebo or lapatinib were selected. PAM50 data, ECOG performance status, visceral disease, number of metastasis, biopsy type, and age were evaluated. A progression-free survival (PFS) Cox model was evaluated. The final model (PAM50MET) with a prespecified cutoff was validated in patients ( n = 261) with HR + /HER2 - advanced breast cancer (aBC) from BOLERO-2 (phase III trial that evaluated exemestane and placebo or everolimus)., Results: In EGF30008, prognostic models with PAM50 plus clinical variables yielded higher C-index values versus models with only PAM50 or clinical variables. The PAM50MET model combined 21 variables: 2 PAM50 subtypes, basal signature, 14 genes, and 4 clinical variables. In EGF30008, the optimized cutoff was associated with PFS [HR = 0.37; 95% confidence interval (CI), 0.29-0.47; P < 0.0001] and overall survival (OS; HR = 0.37; 95% CI, 0.27-0.51; P < 0.0001). The median (months; 95% CI) PFS and OS were 22.24 (19.0-24.9) and not reached in PAM50MET-low versus 9.13 (8.15-11.0) and 33.0 (28.0-40.0) in PAM50MET-high groups, respectively. In BOLERO-2, the PAM50MET-low was associated with better PFS (HR = 0.72; 95% CI, 0.53-0.96; P = 0.028) and OS (HR = 0.51; 95% CI, 0.35-0.69; P < 0.0001). The median (months) (95% CI) PFS and OS were 6.93 (5.57-11.0) and 36.9 (33.4-NA) in PAM50MET-low versus 5.23 (4.2-6.8) and 23.5 (20.2-28.3) in PAM50MET-high groups, respectively., Conclusions: PAM50MET is prognostic in HR + /HER2 - MBC, and further evaluation might help identify candidates for endocrine therapy only or novel therapies., (©2020 American Association for Cancer Research.)

Purpose: T-cell immunoreceptor with Ig and ITIM domain (TIGIT) blockade could represent an alternative therapeutic option to release the immune response in patients with multiple myeloma. Here we analyzed the expression of TIGIT and its ligands poliovirus receptor (PVR) and nectin-2 in the bone marrow (BM) of patients with monoclonal gammopathies and the efficacy of TIGIT blockade activating antimyeloma immunity., Experimental Design: Expression levels of TIGIT and its ligands were characterized by flow cytometry and ELISA. TIGIT blockade was analyzed in in vitro functional assays with peripheral T cells. BM cells were studied with NanoString technology, real-time PCR, and ex vivo patient BM cell models., Results: TIGIT and its ligands are highly expressed in the BM of patients with multiple myeloma, suggesting that may play a role in restraining immune activation. TIGIT blockade depleted FoxP3 + Tregs while increasing proliferation of IFNγ-producing CD4 + T cells from patients with multiple myeloma. PVR ligation inhibited CD8 + T-cell signaling and cell proliferation which could be overcome with anti-TIGIT mAb. However, BM cells showed a remarkable heterogeneity in immune signature. Accordingly, functional ex vivo BM assays revealed that only some patients respond to checkpoint blockade. Thus, response to TIGIT blockade correlated with low frequency of TIGIT + cells and high nectin-2 expression on malignant plasma cells., Conclusions: TIGIT blockade efficiently reinvigorated peripheral T cells from patients with multiple myeloma. However, in the BM, the efficacy of blocking anti-TIGIT mAb to achieve tumor cell death may depend on the expression of TIGIT and nectin-2, becoming potential predictive biomarkers for identifying patients who may benefit from TIGIT blockade., (©2020 American Association for Cancer Research.)

Purpose: AZD5363/capivasertib is a pan-AKT catalytic inhibitor with promising activity in combination with paclitaxel in triple-negative metastatic breast cancer harboring PI3K/AKT-pathway alterations and in estrogen receptor-positive breast cancer in combination with fulvestrant. Here, we aimed to identify response biomarkers and uncover mechanisms of resistance to AZD5363 and its combination with paclitaxel., Experimental Design: Genetic and proteomic markers were analyzed in 28 HER2-negative patient-derived xenografts (PDXs) and in patient samples, and correlated to AZD5363 sensitivity as single agent and in combination with paclitaxel., Results: Four PDX were derived from patients receiving AZD5363 in the clinic which exhibited concordant treatment response. Mutations in PIK3CA / AKT1 and absence of mTOR complex 1 (mTORC1)-activating alterations, for example, in MTOR or TSC1 , were associated with sensitivity to AZD5363 monotherapy. Interestingly, excluding PTEN from the composite biomarker increased its accuracy from 64% to 89%. Moreover, resistant PDXs exhibited low baseline pAKT S473 and residual pS6 S235 upon treatment, suggesting that parallel pathways bypass AKT/S6K1 signaling in these models. We identified two mechanisms of acquired resistance to AZD5363: cyclin D1 overexpression and loss of AKT1 p.E17K., Conclusions: This study provides insight into putative predictive biomarkers of response and acquired resistance to AZD5363 in HER2-negative metastatic breast cancer., (©2020 American Association for Cancer Research.)

Background: HER2-positive (HER2+) breast cancer (BC) comprises all the four PAM50 molecular subtypes. Among these, the HER2-Enriched (HER2-E) appear to be associated with higher pathological complete response (pCR) rates following anti-HER2-based regimens. Here, we present a meta-analysis to validate the association of the HER2-E subtype with pCR following anti-HER2-based neoadjuvant treatments with or without chemotherapy (CT)., Methods: A systematic literature search was performed in February 2019. The primary objective was to compare the association between HER2-E subtype (versus others) and pCR. Selected secondary objectives were to compare the association between 1) HER2-E subtype and pCR in CT-free studies, 2) HER2-E subtype within hormone receptor (HR)-negative and HR+ disease and 3) HR-negative disease (versus HR+) and pCR in all patients and within HER2-E subtype. A random-effect model was applied. The Higgins' I 2 was used to quantify heterogeneity., Results: Sixteen studies were included, 5 of which tested CT-free regimens. HER2-E subtype was significantly associated with pCR in all patients (odds ratio [OR] = 3.50, p < 0.001, I 2  = 33%), in HR+ (OR = 3.61, p < 0.001, I 2  = 1%) and HR-negative tumors (OR = 2.28, p = 0.01, I 2  = 47%). In CT-free studies, HER2-E subtype was associated with pCR in all patients (OR = 5.52, p < 0.001, I 2  = 0%) and in HR + disease (OR = 4.08, p = 0.001, I 2  = 0%). HR-negative status was significantly associated with pCR compared to HR + status in all patients (OR = 2.41, p < 0.001, I 2  = 30%) and within the HER2-E subtype (OR = 1.76, p < 0.001, I 2  = 0%)., Conclusions: The HER2-E biomarker identifies patients with a higher likelihood of achieving a pCR following neoadjuvant anti-HER2-based therapy beyond HR status and CT use. Future trial designs to escalate or de-escalate systemic therapy in HER2+ disease should consider this genomic biomarker., Competing Interests: Declaration of Competing Interest FS has declared travel and accommodation expenses paid by Roche, Pfizer and Celgene. SDP has declared honoraria from Roche, Pfizer, Astra-Zeneca, Novartis, Celgene, Eli Lilly, Amgen and Eisai. AP has declared an immediate family member being employed by Novartis, personal honoraria from Pfizer, Novartis, Roche, MSD Oncology, Lilly and Daiichi Sankyo, travel, accommodations and expenses paid by Daiichi Sankyo, research funding from Roche and Novartis, consulting/advisory role for NanoString Technologies, Amgen, Roche, Novartis, Pfizer and Bristol-Myers Squibb and patent PCT/EP2016/080056: HER2 AS A PREDICTOR OF RESPONSE TO DUAL HER2 BLOCKADE IN THE ABSENCE OF CYTOTOXIC THERAPY. OTHER AUTHORS CoI. PFC had declared consultant role for Novartis, Eli Lilly, Astra Zeneca and Tesaro, honoraria from BMS, Roche, Eli Lilly, Novartis and AstraZeneca, research funding from Novartis, Roche, BMS, Merck-KGa, Italian Ministry of Health, Veneto Secretary of Health and University of Padova. CMP is an equity stock holder and consultant of BioClassifier LLC and is also listed an inventor on patent applications on the Breast PAM50. LAC has declared that Companies who have provided funds to her institution in the past 1–2 years either for her service on advisory/consultative programs or sponsored research were Genentech, Roche, Novartis, Seattle Genetics, G1 Therapeutics, Immunomedics and Innocrin.SP has received honoraria for talks and travel grants from Roche outside of the submitted work and serves as an advisor/consultant to Polyphor. RS has declared research funding from AstraZeneca, GlaxoSmithKline, Gilead Sciences, and PUMA Biotechnology, and consulting/advisory role with compensation for Macrogenics, and Eli Lilly. CKO has declared research funding from AstraZeneca and GlaxoSmithKline, advisory boards for Tolmar Pharmaceuticals, Genentech, and AstraZeneca, DMC for Eli Lilly and stockholder of GeneTex. MFR has declared research funding from GlaxoSmithKline and Genentech. JCB reports employment and stocks with Novartis. The other authors have nothing to declare., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The HER2-enriched (HER2-E) subtype within HER2-positive (HER2+) breast cancer is highly addicted to the HER2 pathway. However, ∼20-60% of HER2+/HER2-E tumors do not achieve a complete response following anti-HER2 therapies. Here we evaluate gene expression data before, during and after neoadjuvant treatment with lapatinib and trastuzumab in HER2+/HER2-E tumors of the PAMELA trial and breast cancer cell lines. Our results reveal that dual HER2 blockade in HER2-E disease induces a low-proliferative Luminal A phenotype both in patient's tumors and in vitro models. These biological changes are more evident in hormone receptor-positive (HR+) disease compared to HR-negative disease. Interestingly, increasing the luminal phenotype with anti-HER2 therapy increased sensitivity to CDK4/6 inhibition. Finally, discontinuation of HER2-targeted therapy in vitro, or acquired resistance to anti-HER2 therapy, leads to restoration of the original HER2-E phenotype. Our findings support the use of maintenance anti-HER2 therapy and the therapeutic exploitation of subtype switching with CDK4/6 inhibition.

Background: Identification of HER2-positive breast cancers with high anti-HER2 sensitivity could help de-escalate chemotherapy. Here, we tested a clinically applicable RNA-based assay that combines ERBB2 and the HER2-enriched (HER2-E) intrinsic subtype in HER2-positive disease treated with dual HER2-blockade without chemotherapy., Methods: A research-based PAM50 assay was applied in 422 HER2-positive tumors from five II-III clinical trials (SOLTI-PAMELA, TBCRC023, TBCRC006, PER-ELISA, EGF104090). In SOLTI-PAMELA, TBCRC023, TBCRC006, and PER-ELISA, all patients had early disease and were treated with neoadjuvant lapatinib or pertuzumab plus trastuzumab for 12-24 weeks. Primary outcome was pathological complete response (pCR). In EGF104900, 296 women with advanced disease were randomized to receive either lapatinib alone or lapatinib plus trastuzumab. Progression-free survival (PFS), overall response rate (ORR), and overall survival (OS) were evaluated., Results: A total of 305 patients with early and 117 patients with advanced HER2-positive disease were analyzed. In early disease, HER2-E represented 83.8% and 44.7% of ERBB2-high and ERBB2-low tumors, respectively. Following lapatinib and trastuzumab, the HER2-E and ERBB2 (HER2-E/ERBB2)-high group showed a higher pCR rate compared to the rest (44.5%, 95% confidence interval [CI] = 35.4% to 53.9% vs 11.6%, 95% CI = 6.9% to 18.0%; adjusted odds ratio [OR] = 6.05, 95% CI = 3.10 to 11.80, P < .001). Similar findings were observed with neoadjuvant trastuzumab and pertuzumab (pCR rate of 66.7% in HER2-E/ERBB2-high, 95% CI = 22.3% to 95.7% vs 14.7% in others, 95% CI = 4.9% to 31.1%; adjusted OR = 11.60, 95% CI = 1.66 to 81.10, P = .01). In the advanced setting, the HER2-E/ERBB2-high group was independently associated with longer PFS (hazard ratio [HR] = 0.52, 95% CI = 0.35 to 0.79, P < .001); higher ORR (16.3%, 95% CI = 8.9% to 26.2% vs 3.7%, 95% CI = 0.8% to 10.3%, P = .02); and longer OS (HR = 0.66, 95% CI = 0.44 to 0.97, P = .01)., Conclusions: Combining HER2-E subtype and ERBB2 mRNA into a single assay identifies tumors with high responsiveness to HER2-targeted therapy. This biomarker could help de-escalate chemotherapy in approximately 40% of patients with HER2-positive breast cancer., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Background: Changes in the clinical subtype (CS) and intrinsic subtype (IS) between breast cancer (BC) metastases and corresponding primary tumours have been reported. However, their relationship with tumour genomic changes remains poorly characterised. Here, we analysed the association between genomic remodelling and subtype conversion in paired primary and metastatic BC samples., Methods: A total of 57 paired primary and metastatic tumours from GEICAM/2009-03 (ConvertHER, NCT01377363) study participants with centrally assessed CS (n = 57) and IS (n = 46) were analysed. Targeted capture and next-generation sequencing of 202 genes on formalin-fixed paraffin-embedded samples was performed. The cancer cell fraction (CCF) of mutations in primary and metastatic pairs was estimated as a surrogate of tumour clonal architecture. Changes in mutation CCF between matched primary and metastatic tumours were analysed in the presence or absence of subtype conversion., Findings: CS conversion occurred in 24.6% and IS conversion occurred in 36.9% of metastases. Primary tumours and metastases had a median of 11 (range, 3-29) and 9 (range, 1-38) mutations, respectively (P = 0.05). Overall, mutations in metastases showed a higher estimated CCF than in primary tumours (median CCF, 0.51 and 0.47, respectively; P = 0.042), consistent with increased clonal homogeneity. The increase in mutation CCF was significant in CS-converted (P = 0.04) but not in IS-converted (P = 0.48) metastases. Clonal remodelling was highest in metastases from hormone receptor-positive and human epidermal growth factor 2 (HER2)-positive tumours (P = 0.006)., Conclusions: Mutations in BC metastases showed significantly higher estimated CCF than primary tumours. CCF changes were more prominent in metastases with CS conversion. Our findings suggest that changes in BC subtypes are linked to clonal remodelling during BC evolution., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

TMPRSS2-ERG expression in blood has been correlated with low docetaxel benefit in metastatic castration-resistant prostate cancer (mCRPC). This multicenter study aimed to prospectively asses its role as a taxane-resistance biomarker in blood and retrospectively in tumors, exploring also the impact of prior abiraterone/enzalutamide (A/E) in patients and in vitro. TMPRSS2-ERG was tested by quantitative reverse-transcription PCR. We included 204 patients (137 blood and 124 tumor samples) treated with taxanes. TMPRSS2-ERG expression was correlated with prostate-specific antigen (PSA)-progression-free survival (PFS), radiological-PFS (RX-PFS), and overall survival (OS). Independent association with survival was evaluated by multivariate Cox modeling. In vitro ERG knockdown and combinatorial and sequential experiments with enzalutamide and docetaxel were performed in VCaP cells. Prior A/E (HR 1.8, 95% CI 1.2-2.8) and blood TMPRSS2-ERG detection (HR 2, 95% CI 1.1-3.7) were independently associated to lower PSA-PFS. In patients without prior A/E, blood and tumor TMPRSS2-ERG independently predicted lower PSA-PFS (HR 3.3, 95% CI 1.4-7.9 and HR 1.8, 95% CI 1.02-3.3, respectively) to taxanes. When prior A/E was administered, TMPRSS2-ERG was not associated with outcome. There was a significant interaction between blood TMPRSS2-ERG and prior A/E related to PSA-PFS (p = 0.032) and RX-PFS (p = 0.009). In vitro stable ERG inhibition did not sensitize VCaP cells to docetaxel. Concomitant enzalutamide and taxanes were synergistic, but prior enzalutamide reduced docetaxel cytotoxicity in VCaP cells. Enzalutamide induced the expression of neuroendocrine markers and reduced that of E-cadherin. We conclude that prior hormone-therapy may influence taxanes response and TMPRSS2-ERG prognostic value. Thus, multiple and sequential biomarkers are needed in CRPC follow-up evaluation., (© 2019 UICC.)

Biological changes that occur during metastatic progression of breast cancer are still incompletely characterized. In this study, we compared intrinsic molecular subtypes and gene expression in 123 paired primary and metastatic tissues from breast cancer patients. Intrinsic subtype was identified using a PAM50 classifier and χ 2 tests determined the differences in variable distribution. The rate of subtype conversion was 0% in basal-like tumors, 23.1% in HER2-enriched (HER2-E) tumors, 30.0% in luminal B tumors, and 55.3% in luminal A tumors. In 40.2% of cases, luminal A tumors converted to luminal B tumors, whereas in 14.3% of cases luminal A and B tumors converted to HER2-E tumors. We identified 47 genes that were expressed differentially in metastatic versus primary disease. Metastatic tumors were enriched for proliferation-related and migration-related genes and diminished for luminal-related genes. Expression of proliferation-related genes were better at predicting overall survival in metastatic disease (OSmet) when analyzed in metastatic tissue rather than primary tissue. In contrast, a basal-like gene expression signature was better at predicting OSmet in primary disease compared with metastatic tissue. We observed correlations between time to tumor relapse and the magnitude of changes of proliferation, luminal B, or HER2-E signatures in metastatic versus primary disease. Although the intrinsic subtype was largely maintained during metastatic progression, luminal/HER2-negative tumors acquired a luminal B or HER2-E profile during metastatic progression, likely reflecting tumor evolution or acquisition of estrogen independence. Overall, our analysis revealed the value of stratifying gene expression by both cancer subtype and tissue type, providing clinicians more refined tools to evaluate prognosis and treatment. Cancer Res; 77(9); 2213-21. ©2017 AACR ., (©2017 American Association for Cancer Research.)

Background: HER2-positive breast cancer consists of four intrinsic molecular subtypes-luminal A, luminal B, HER2-enriched, and basal-like-and a normal-like subtype, with the HER2-enriched subtype having the highest activation of the EGFR-HER2 pathway. We aimed to test the hypothesis that patients with the HER2-enriched subtype benefit the most from dual HER2 blockade., Methods: PAMELA is an open-label, single-group, phase 2 trial done in 19 hospitals in Spain. We recruited female patients aged at least 18 years with previously untreated, centrally confirmed HER2-positive, stage I-IIIA invasive breast cancer regardless of hormone receptor status. Patients were given lapatinib (1000 mg per day orally) and trastuzumab (loading dose of 8 mg/kg, followed by 6 mg/kg every 3 weeks intravenously) for 18 weeks; hormone receptor-positive patients were additionally given letrozole (2·5 mg per day orally; if menopausal) or tamoxifen (20 mg per day orally; if premenopausal). Surgery was done 1-3 weeks after the last dose of study treatment. Intrinsic molecular subtypes of tumour biopsy samples taken at baseline (day 0) and day 14 were determined with the PAM50 predictor. The primary outcome was the ability of the HER2-enriched subtype to predict pathological complete response at the time of surgery. The primary outcome was assessed in the evaluable population (ie, all patients who had initial tumour biopsy samples available and who underwent definitive surgery) and safety was assessed in all patients who received at least one part of study treatment. This study is registered with ClinicalTrials.gov, number NCT01973660, and is completed., Findings: Between Oct 28, 2013, and Nov 26, 2015, we recruited 151 patients, of whom 14 (9%) discontinued treatment and 137 (91%) completed treatment as planned. At baseline, most patients had the HER2-enriched subtype (101 [67%]), followed by luminal A (22 [15%]), luminal B (16 [11%]), basal-like (nine [6%]), and normal-like (three [2%]) subtypes. At the time of surgery, 46 (30%, 95% CI 23-39) of 151 patients had pathological complete response in the breast. 41 (41%, 31-51) of 101 patients with the HER2-enriched subtype and five (10%, 4-23) of 50 patients with non-HER2-enriched subtypes achieved pathological complete response at the time of surgery (odds ratio 6·2, 95% CI 2·3-16·8; p=0·0004)., Interpretation: The HER2-enriched subtype can identify patients with HER2-positive breast cancer who are likely to benefit from dual HER2 blockade therapies., Funding: GlaxoSmithKline, Susan Komen Foundation, CERCA Programme-Generalitat de Catalunya, Banco Bilbao Vizcaya Argentaria Foundation, Pas a Pas, and the Breast Cancer Research Foundation., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

PAM50/Prosigna gene expression-based assay identifies three categorical risk of relapse groups (ROR-low, ROR-intermediate and ROR-high) in post-menopausal patients with estrogen receptor estrogen receptor-positive (ER+)/ HER2-negative (HER2-) early breast cancer. Low risk patients might not need adjuvant chemotherapy since their risk of distant relapse at 10-years is below 10% with endocrine therapy only. In this study, 517 consecutive patients with ER+/HER2- and node-negative disease were evaluated for Ki67 and Prosigna. Most of Luminal A tumors (65.6%) and ROR-low tumors (70.9%) had low Ki67 values (0-10%); however, the percentage of patients with ROR-medium or ROR-high disease within the Ki67 0-10% group was 42.7% (with tumor sizes ≤2 cm) and 33.9% (with tumor sizes > 2 cm). Finally, we found that the optimal Ki67 cutoff for identifying Luminal A or ROR-low tumors was 14%. Ki67 as a surrogate biomarker in identifying Prosigna low-risk outcome patients or Luminal A disease in the clinical setting is unreliable. In the absence of a well-validated prognostic gene expression-based assay, the optimal Ki67 cutoff for identifying low-risk outcome patients or Luminal A disease remains at 14%.

Background: There are currently no biomarkers for early breast cancer patient populations at risk of bone metastasis. Identification of mediators of bone metastasis could be of clinical interest., Methods: A de novo unbiased screening approach based on selection of highly bone metastatic breast cancer cells in vivo was used to determine copy number aberrations (CNAs) associated with bone metastasis. The CNAs associated with bone metastasis were examined in independent primary breast cancer datasets with annotated clinical follow-up. The MAF gene encoded within the CNA associated with bone metastasis was subjected to gain and loss of function validation in breast cancer cells (MCF7, T47D, ZR-75, and 4T1), its downstream mechanism validated, and tested in clinical samples. A multivariable Cox cause-specific hazard model with competing events (death) was used to test the association between 16q23 or MAF and bone metastasis. All statistical tests were two-sided., Results: 16q23 gain CNA encoding the transcription factor MAF mediates breast cancer bone metastasis through the control of PTHrP. 16q23 gain (hazard ratio (HR) for bone metastasis = 14.5, 95% confidence interval (CI) = 6.4 to 32.9, P < .001) as well as MAF overexpression (HR for bone metastasis = 2.5, 95% CI = 1.7 to 3.8, P < .001) in primary breast tumors were specifically associated with risk of metastasis to bone but not to other organs., Conclusions: These results suggest that MAF is a mediator of breast cancer bone metastasis. 16q23 gain or MAF protein overexpression in tumors may help to select patients at risk of bone relapse., (© The Author 2015. Published by Oxford University Press.)

Background: The clinical impact of the biological heterogeneity within HER2-positive (HER2+) breast cancer is not fully understood. Here, we evaluated the molecular features and survival outcomes of the intrinsic subtypes within HER2+ breast cancer., Methods: We interrogated The Cancer Genome Atlas (n = 495) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) datasets (n = 1730) of primary breast cancers for molecular data derived from DNA, RNA and protein, and determined intrinsic subtype. Clinical HER2 status was defined according to American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines or DNA copy-number aberration by single nucleotide polymorphism arrays. Cox models tested the prognostic significance of each variable in patients not treated with trastuzumab (n = 1711)., Results: Compared with clinically HER2 (cHER2)-negative breast cancer, cHER2+ breast cancer had a higher frequency of the HER2-enriched (HER2E) subtype (47.0% vs 7.1%) and a lower frequency of Luminal A (10.7% vs 39.0%) and Basal-like (14.1% vs 23.4%) subtypes. The likelihood of cHER2-positivity in HER2E, Luminal B, Basal-like and Luminal A subtypes was 64.6%, 20.0%, 14.4% and 7.3%, respectively. Within each subtype, only 0.3% to 3.9% of genes were found differentially expressed between cHER2+ and cHER2-negative tumors. Within cHER2+ tumors, HER2 gene and protein expression was statistically significantly higher in the HER2E and Basal-like subtypes than either luminal subtype. Neither cHER2 status nor the new 10-subtype copy number-based classification system (IntClust) added independent prognostic value to intrinsic subtype., Conclusions: When the intrinsic subtypes are taken into account, cHER2-positivity does not translate into large changes in the expression of downstream signaling pathways, nor does it affect patient survival in the absence of HER2 targeting., (© The Author 2014. Published by Oxford University Press.)

Breast cancer is a heterogeneous disease, divisible into a variable number of clinical subtypes. A fundamental question is how many etiological classes underlie the clinical spectrum of breast cancer? An etiological subtype reflects a grouping with a common set of causes, whereas a clinical subtype represents a grouping with similar prognosis and/or prediction. Herein, we review the evidence for breast cancer etiological heterogeneity. We then evaluate the etiological evidence with mRNA profiling data. A bimodal age distribution at diagnosis with peak frequencies near ages 50 and 70 years is a fundamental characteristic of breast cancer for important tumor features, clinical characteristics, risk factor profiles, and molecular subtypes. The bimodal peak frequencies at diagnosis divide breast cancer overall into a "mixture" of two main components in varying proportions in different cancer populations. The first breast cancer tends to arise early in life with modal age-at-diagnosis near 50 years and generally behaves aggressively. The second breast cancer occurs later in life with modal age near 70 years and usually portends a more indolent clinical course. These epidemiological and molecular data are consistent with a two-component mixture model and compatible with a hierarchal view of breast cancers arising from two main cell types of origin. Notwithstanding the potential added value of more detailed categorizations for personalized breast cancer treatment, we suggest that the development of better criteria to identify the two proposed etiologic classes would advance breast cancer research and prevention., (Published by Oxford University Press 2014.)

BRCA1-mutated breast cancer is associated with basal-like disease; however, it is currently unclear if the presence of a BRCA1 mutation depicts a different entity within this subgroup. In this study, we compared the molecular features among basal-like tumors with and without BRCA1 mutations. Fourteen patients with BRCA1-mutated (nine germline and five somatic) tumors and basal-like disease, and 79 patients with BRCA1 non-mutated tumors and basal-like disease, were identified from the cancer genome atlas dataset. The following molecular data types were evaluated: global gene expression, selected protein and phospho-protein expression, global miRNA expression, global DNA methylation, total number of somatic mutations, TP53 and PIK3CA somatic mutations, and global DNA copy-number aberrations. For intrinsic subtype identification, we used the PAM50 subtype predictor. Within the basal-like disease, we observed minor molecular differences in terms of gene, protein, and miRNA expression, and DNA methylation variation, according to BRCA1 status (either germinal or somatic). However, there were significant differences according to average number of mutations and DNA copy-number aberrations, and four amplified regions (2q32.2, 3q29, 6p22.3, and 22q12.2), which are characteristic in high-grade serous ovarian carcinomas, were observed in both germline and somatic BRCA1-mutated breast tumors. These results suggest that minor, but potentially relevant, baseline molecular features exist among basal-like tumors according to BRCA1 status. Additional studies are needed to better clarify if BRCA1 genetic status is an independent prognostic feature, and more importantly, if BRCA1 mutation status is a predictive biomarker of benefit from DNA-damaging agents among basal-like disease.

Triple-negative (TN) and basal-like (BL) breast cancer definitions have been used interchangeably to identify breast cancers that lack expression of the hormone receptors and overexpression and/or amplification of HER2. However, both classifications show substantial discordance rates when compared to each other. Here, we molecularly characterize TN tumors and BL tumors, comparing and contrasting the results in terms of common patterns and distinct patterns for each. In total, when testing 412 TN and 473 BL tumors, 21.4% and 31.5% were identified as non-BL and non-TN, respectively. TN tumors identified as luminal or HER2-enriched (HER2E) showed undistinguishable overall gene expression profiles when compared versus luminal or HER2E tumors that were not TN. Similar findings were observed within BL tumors regardless of their TN status, which suggests that molecular subtype is preserved regardless of individual marker results. Interestingly, most TN tumors identified as HER2E showed low HER2 expression and lacked HER2 amplification, despite the similar overall gene expression profiles to HER2E tumors that were clinically HER2-positive. Lastly, additional genomic classifications were examined within TN and BL cancers, most of which were highly concordant with tumor intrinsic subtype. These results suggest that future clinical trials focused on TN disease should consider stratifying patients based upon BL versus non-BL gene expression profiles, which appears to be the main biological difference seen in patients with TN breast cancer.

Background: Many methodologies have been used in research to identify the "intrinsic" subtypes of breast cancer commonly known as Luminal A, Luminal B, HER2-Enriched (HER2-E) and Basal-like. The PAM50 gene set is often used for gene expression-based subtyping; however, surrogate subtyping using panels of immunohistochemical (IHC) markers are still widely used clinically. Discrepancies between these methods may lead to different treatment decisions., Methods: We used the PAM50 RT-qPCR assay to expression profile 814 tumors from the GEICAM/9906 phase III clinical trial that enrolled women with locally advanced primary invasive breast cancer. All samples were scored at a single site by IHC for estrogen receptor (ER), progesterone receptor (PR), and Her2/neu (HER2) protein expression. Equivocal HER2 cases were confirmed by chromogenic in situ hybridization (CISH). Single gene scores by IHC/CISH were compared with RT-qPCR continuous gene expression values and "intrinsic" subtype assignment by the PAM50. High, medium, and low expression for ESR1, PGR, ERBB2, and proliferation were selected using quartile cut-points from the continuous RT-qPCR data across the PAM50 subtype assignments., Results: ESR1, PGR, and ERBB2 gene expression had high agreement with established binary IHC cut-points (area under the curve (AUC) ≥ 0.9). Estrogen receptor positivity by IHC was strongly associated with Luminal (A and B) subtypes (92%), but only 75% of ER negative tumors were classified into the HER2-E and Basal-like subtypes. Luminal A tumors more frequently expressed PR than Luminal B (94% vs 74%) and Luminal A tumors were less likely to have high proliferation (11% vs 77%). Seventy-seven percent (30/39) of ER-/HER2+ tumors by IHC were classified as the HER2-E subtype. Triple negative tumors were mainly comprised of Basal-like (57%) and HER2-E (30%) subtypes. Single gene scoring for ESR1, PGR, and ERBB2 was more prognostic than the corresponding IHC markers as shown in a multivariate analysis., Conclusions: The standard immunohistochemical panel for breast cancer (ER, PR, and HER2) does not adequately identify the PAM50 gene expression subtypes. Although there is high agreement between biomarker scoring by protein immunohistochemistry and gene expression, the gene expression determinations for ESR1 and ERBB2 status was more prognostic.

Introduction: In breast cancer, gene expression analyses have defined five tumor subtypes (luminal A, luminal B, HER2-enriched, basal-like and claudin-low), each of which has unique biologic and prognostic features. Here, we comprehensively characterize the recently identified claudin-low tumor subtype., Methods: The clinical, pathological and biological features of claudin-low tumors were compared to the other tumor subtypes using an updated human tumor database and multiple independent data sets. These main features of claudin-low tumors were also evaluated in a panel of breast cancer cell lines and genetically engineered mouse models., Results: Claudin-low tumors are characterized by the low to absent expression of luminal differentiation markers, high enrichment for epithelial-to-mesenchymal transition markers, immune response genes and cancer stem cell-like features. Clinically, the majority of claudin-low tumors are poor prognosis estrogen receptor (ER)-negative, progesterone receptor (PR)-negative, and epidermal growth factor receptor 2 (HER2)-negative (triple negative) invasive ductal carcinomas with a high frequency of metaplastic and medullary differentiation. They also have a response rate to standard preoperative chemotherapy that is intermediate between that of basal-like and luminal tumors. Interestingly, we show that a group of highly utilized breast cancer cell lines, and several genetically engineered mouse models, express the claudin-low phenotype. Finally, we confirm that a prognostically relevant differentiation hierarchy exists across all breast cancers in which the claudin-low subtype most closely resembles the mammary epithelial stem cell., Conclusions: These results should help to improve our understanding of the biologic heterogeneity of breast cancer and provide tools for the further evaluation of the unique biology of claudin-low tumors and cell lines.