Ander Urruticoechea

Proliferation Marker Ki-67 in Early Breast Cancer

Molecular markers have been extensively investigated with a view to providing early and accurate information on long-term outcome and prediction of response to treatment of early breast cancer. Proliferation is a key feature of the progression of tumors and is now widely estimated by the immunohistochemical assessment of the nuclear antigen Ki-67. The expression of Ki-67 correlates with other measurements of proliferation, including S-phase and bromodeoxyuridine uptake. High Ki-67 is a sign of poor prognosis associated with a good chance of clinical response to chemotherapy, but its independent significance is modest and does not merit measurements in most routine clinical scenarios. However, its application as a pharmacodynamic intermediate marker of the effectiveness of medical therapy holds great promise for rapid evaluation of new drugs.

Molecular response to aromatase inhibitor treatment in primary breast cancer

BackgroundAromatase inhibitors such as anastrozole and letrozole are highly effective suppressants of estrogen synthesis in postmenopausal women and are the most effective endocrine treatments for hormone receptor positive breast cancer in such women. Little is known of the molecular effects of these agents on human breast carcinomas in vivo.MethodsWe randomly assigned primary estrogen receptor positive breast cancer patients to treatment with anastrozole or letrozole for 2 weeks before surgery. Expression profiling using cDNA arrays was conducted on pretreatment and post-treatment biopsies. Sample pairs from 34 patients provided sufficient RNA for analysis.ResultsProfound changes in gene expression were seen with both aromatase inhibitors, including many classical estrogen-dependent genes such as TFF1, CCND1, PDZK1 and AGR2, but also many other genes that are likely to represent secondary responses; decrease in the expression of proliferation-related genes were particularly prominent. Many upregulated genes are involved in extracellular matrix remodelling, including collagens and members of the small leucine-rich proteoglycan family (LUM, DCN, and ASPN). No significant differences were seen between letrozole and anastrozole in terms of molecular effects. The gene changes were integrated into a Global Index of Dependence on Estrogen (GIDE), which enumerates the genes changing by at least twofold with therapy. The GIDE varied markedly between tumours and related significantly to pretreatment levels of HER2 and changes in immunohistochemically detected Ki67.ConclusionOur findings identify the transcriptional signatures associated with aromatase inhibitor treatment of primary breast tumours. Larger datasets using this approach should enable identification of estrogen-dependent molecular changes, which are the determinants of benefit or resistance to endocrine therapy.

RANK Induces Epithelial–Mesenchymal Transition and Stemness in Human Mammary Epithelial Cells and Promotes Tumorigenesis and Metastasis

Paracrine signaling through receptor activator of NF-κB (RANK) pathway mediates the expansion of mammary epithelia that occurs during pregnancy, and activation of RANK pathway promotes mammary tumorigenesis in mice. In this study we extend these previous data to human cells and show that the RANK pathway promotes the development of mammary stem cells and breast cancer. Overexpression of RANK (FL-RANK) in a panel of tumoral and normal human mammary cells induces the expression of breast cancer stem and basal/stem cell markers. High levels of RANK in untransformed MCF10A cells induce changes associated with both stemness and transformation, including mammary gland reconstitution, epithelial-mesenchymal transition (EMT), increased migration, and anchorage-independent growth. In addition, spheroids of RANK overexpressing MCF10A cells display disrupted acinar formation, impair growth arrest and polarization, and luminal filling. RANK overexpression in tumor cells with nonfunctional BRCA1 enhances invasiveness in acinar cultures and increases tumorigenesis and metastasis in immunodeficient mice. High levels of RANK were found in human primary breast adenocarcinomas that lack expression of the hormone receptors, estrogen and progesterone, and in tumors with high pathologic grade and proliferation index; high RANK/RANKL expression was significantly associated with metastatic tumors. Together, our findings show that RANK promotes tumor initiation, progression, and metastasis in human mammary epithelial cells by increasing the population of CD44(+)CD24(-) cells, inducing stemness and EMT. These results suggest that RANK expression in primary breast cancer associates with poor prognosis.

Phase Ib study of buparlisib plus trastuzumab in patients with HER2-positive advanced or metastatic breast cancer that has progressed on trastuzumab-based therapy

Purpose: Phosphoinositide 3-kinase (PI3K)/AKT/mTOR pathway activation in patients with HER2-positive (HER2+) breast cancer has been implicated in de novo and acquired trastuzumab resistance. The purpose of this study was to determine the clinical activity of the PI3K inhibitor buparlisib (BKM120) in patients with HER2+ advanced/metastatic breast cancer resistant to trastuzumab-based therapy. Experimental Design: In the dose-escalation portion of this phase I/II study, patients with trastuzumab-resistant locally advanced or metastatic HER2+ breast cancer were treated with daily oral doses of buparlisib and weekly intravenous trastuzumab (2 mg/kg). Dose escalation was guided by a Bayesian logistic regression model with overdose control. Results: Of 18 enrolled patients, 17 received buparlisib. One dose-limiting toxicity of grade 3 general weakness was reported at the 100-mg/day dose level (the single-agent maximum tolerated dose) and this dose level was declared the recommended phase II dose (RP2D) of buparlisib in combination with trastuzumab. Common (>25%) adverse events included rash (39%), hyperglycemia (33%), and diarrhea (28%). The pharmacokinetic profile of buparlisib was not affected by its combination with trastuzumab. At the RP2D, there were two (17%) partial responses, 7 (58%) patients had stable disease (≥6 weeks), and the disease control rate was 75%. Pharmacodynamic studies showed inhibition of the PI3K/AKT/mTOR and RAS/MEK/ERK pathways. Conclusions: In this patient population, the combination of buparlisib and trastuzumab was well tolerated, and preliminary signs of clinical activity were observed. The phase II portion of this study will further explore the safety and efficacy of this combination at the RP2D. Clin Cancer Res; 20(7); 1935–45. ©2014 AACR.

Novel Inhibitors of Fatty Acid Synthase with Anticancer Activity

Purpose: Fatty acid synthase (FASN) is overexpressed in human breast carcinoma. The natural polyphenol (−)-epigallocatechin-3-gallate blocks in vitro FASN activity and leads to apoptosis in breast cancer cells without any effects on carnitine palmitoyltransferase-1 (CPT-1) activity, and in vivo, does not decrease body weight. We synthesized a panel of new polyphenolic compounds and tested their effects on breast cancer models. Experimental Design: We evaluated the in vitro effects of the compounds on breast cancer cell growth (SK-Br3, MCF-7, and MDA-MB-231), apoptosis [as assessed by cleavage of poly(ADP-ribose) polymerase], cell signaling (HER2, ERK1/2, and AKT), and fatty acid metabolism enzymes (FASN and CPT-1). In vivo, we have evaluated their antitumor activity and their effect on body weight in a mice model of BT474 breast cancer cells. Results: Two compounds potently inhibited FASN activity and showed high cytotoxicity. Moreover, the compounds induced apoptosis and caused a marked decrease in the active forms of HER2, AKT, and ERK1/2 proteins. Interestingly, the compounds did not stimulate CPT-1 activity in vitro. We show evidence that one of the FASN inhibitors blocked the growth of BT474 breast cancer xenografts and did not induce weight loss in vivo. Conclusions: The synthesized polyphenolic compounds represent a novel class of FASN inhibitors, with in vitro and in vivo anticancer activity, that do not exhibit cross-activation of β-oxidation and do not induce weight loss in animals. One of the compounds blocked the growth of breast cancer xenografts. These FASN inhibitors may represent new agents for breast cancer treatment. (Clin Cancer Res 2009;15(24):7608–15)

Biological reprogramming in acquired resistance to endocrine therapy of breast cancer

Endocrine therapies targeting the proliferative effect of 17β-estradiol through estrogen receptor α (ERα) are the most effective systemic treatment of ERα-positive breast cancer. However, most breast tumors initially responsive to these therapies develop resistance through molecular mechanisms that are not yet fully understood. The long-term estrogen-deprived (LTED) MCF7 cell model has been proposed to recapitulate acquired resistance to aromatase inhibitors in postmenopausal women. To elucidate this resistance, genomic, transcriptomic and molecular data were integrated into the time course of MCF7–LTED adaptation. Dynamic and widespread genomic changes were observed, including amplification of the ESR1 locus consequently linked to an increase in ERα. Dynamic transcriptomic profiles were also observed that correlated significantly with genomic changes and were predicted to be influenced by transcription factors known to be involved in acquired resistance or cell proliferation (for example, interferon regulatory transcription factor 1 and E2F1, respectively) but, notably, not by canonical ERα transcriptional function. Consistently, at the molecular level, activation of growth factor signaling pathways by EGFR/ERBB/AKT and a switch from phospho-Ser118 (pS118)- to pS167-ERα were observed during MCF7–LTED adaptation. Evaluation of relevant clinical settings identified significant associations between MCF7–LTED and breast tumor transcriptome profiles that characterize ERα-negative status, early response to letrozole and tamoxifen, and recurrence after tamoxifen treatment. In accordance with these profiles, MCF7–LTED cells showed increased sensitivity to inhibition of FGFR-mediated signaling with PD173074. This study provides mechanistic insight into acquired resistance to endocrine therapies of breast cancer and highlights a potential therapeutic strategy.

A novel inhibitor of fatty acid synthase shows activity against HER2+ breast cancer xenografts and is active in anti-HER2 drug-resistant cell lines.

IntroductionInhibiting the enzyme Fatty Acid Synthase (FASN) leads to apoptosis of breast carcinoma cells, and this is linked to human epidermal growth factor receptor 2 (HER2) signaling pathways in models of simultaneous expression of FASN and HER2.MethodsIn a xenograft model of breast carcinoma cells that are FASN+ and HER2+, we have characterised the anticancer activity and the toxicity profile of G28UCM, the lead compound of a novel family of synthetic FASN inhibitors. In vitro, we analysed the cellular and molecular interactions of combining G28UCM with anti-HER drugs. Finally, we tested the cytotoxic ability of G28UCM on breast cancer cells resistant to trastuzumab or lapatinib, that we developed in our laboratory.ResultsIn vivo, G28UCM reduced the size of 5 out of 14 established xenografts. In the responding tumours, we observed inhibition of FASN activity, cleavage of poly-ADPribose polymerase (PARP) and a decrease of p-HER2, p- protein kinase B (AKT) and p-ERK1/2, which were not observed in the nonresponding tumours. In the G28UCM-treated animals, no significant toxicities occurred, and weight loss was not observed. In vitro, G28UCM showed marked synergistic interactions with trastuzumab, lapatinib, erlotinib or gefitinib (but not with cetuximab), which correlated with increases in apoptosis and with decreases in the activation of HER2, extracellular signal-regulated kinase (ERK)1/2 and AKT. In trastuzumab-resistant and in lapatinib-resistant breast cancer cells, in which trastuzumab and lapatinib were not effective, G28UCM retained the anticancer activity observed in the parental cells.ConclusionsG28UCM inhibits fatty acid synthase (FASN) activity and the growth of breast carcinoma xenografts in vivo, and is active in cells with acquired resistance to anti-HER2 drugs, which make it a candidate for further pre-clinical development.

Basal/HER2 breast carcinomas: Integrating molecular taxonomy with cancer stem cell dynamics to predict primary resistance to trastuzumab (Herceptin)

High rates of inherent primary resistance to the humanized monoclonal antibody trastuzumab (Herceptin) are frequent among HER2 gene-amplified breast carcinomas in both metastatic and adjuvant settings. The clinical efficacy of trastuzumab is highly correlated with its ability to specifically and efficiently target HER2-driven populations of breast cancer stem cells (CSCs). Intriguingly, many of the possible mechanisms by which cancer cells escape trastuzumab involve many of the same biomarkers that have been implicated in the biology of CS-like tumor-initiating cells. In the traditional, one-way hierarchy of CSCs in which all cancer cells descend from special self-renewing CSCs, HER2-positive CSCs can occur solely by self-renewal. Therefore, by targeting CSC self-renewal and resistance, trastuzumab is expected to induce tumor shrinkage and further reduce breast cancer recurrence rates when used alongside traditional therapies. In a new, alternate model, more differentiated non-stem cancer cells can revert to trastuzumab-refractory, CS-like cells via the activation of intrinsic or microenvironmental paths-to-stemness, such as the epithelial-to-mesenchymal transition (EMT). Alternatively, stochastic transitions of trastuzumab-responsive CSCs might also give rise to non-CSC cellular states that lack major attributes of CSCs and, therefore, can remain “hidden” from trastuzumab activity. Here, we hypothesize that a better understanding of the CSC/non-CSC social structure within HER2-overexpressing breast carcinomas is critical for trastuzumab-based treatment decisions in the clinic. First, we decipher the biological significance of CSC features and the EMT on the molecular effects and efficacy of trastuzumab in HER2-positive breast cancer cells. Second, we reinterpret the genetic heterogeneity that differentiates trastuzumab-responders from non-responders in terms of CSC cellular states. Finally, we propose that novel predictive approaches aimed at better forecasting early tumor responses to trastuzumab should identify biological determinants that causally underlie the intrinsic flexibility of HER2-positive CSCs to “enter” into or “exit” from trastuzumab-sensitive states. An accurate integration of CSC cellular states and EMT-related biomarkers with the currently available breast cancer molecular taxonomy may significantly improve our ability to make a priori decisions about whether patients belonging to HER2 subtypes differentially enriched with a “mesenchymal transition signature” (e.g., luminal/HER2 vs. basal/HER2) would distinctly benefit from trastuzumab-based therapy ab initio.

Biological convergence of cancer signatures

Gene expression profiling has identified cancer prognostic and predictive signatures with superior performance to conventional histopathological or clinical parameters. Consequently, signatures are being incorporated into clinical practice and will soon influence everyday decisions in oncology. However, the slight overlap in the gene identity between signatures for the same cancer type or condition raises questions about their biological and clinical implications. To clarify these issues, better understanding of the molecular properties and possible interactions underlying apparently dissimilar signatures is needed. Here, we evaluated whether the signatures of 24 independent studies are related at the genome, transcriptome or proteome levels. Significant associations were consistently observed across these molecular layers, which suggest the existence of a common cancer cell phenotype. Convergence on cell proliferation and death supports the pivotal involvement of these processes in prognosis, metastasis and treatment response. In addition, functional and molecular associations were identified with the immune response in different cancer types and conditions that complement the contribution of cell proliferation and death. Examination of additional, independent, cancer datasets corroborated our observations. This study proposes a comprehensive strategy for interpreting cancer signatures that reveals common design principles and systems-level properties.

Novel anti-fatty acid synthase compounds with anti-cancer activity in HER2+ breast cancer.

Fatty acid synthase (FASN) expression and activity has emerged as a common phenotype in most human carcinomas, including breast cancer, and its expression is tightly linked to HER2 signaling pathways. The development of inhibitors of FASN activity has consequently appeared as a novel antitarget modality for treating cancer. However, the clinical use of FASN inhibitors, such as cerulenin, C75, and epigallocatechin 3‐gallate (EGCG), is limited by anorexia and induced body weight loss or by its low in vivo potency and stability. Here, we summarize the design and development of G28UCM, the lead‐compound of a novel family of synthetic FASN inhibitors, with both in vitro and in vivo activity in a human breast cancer model of FASN+ and HER2+.