Jeff Sperinde

Trastuzumab has preferential activity against breast cancers driven by HER2 homodimers

In breast cancer cells with HER2 gene amplification, HER2 receptors exist on the cell surface as monomers, homodimers, and heterodimers with EGFR/HER3. The therapeutic antibody trastuzumab, an approved therapy for HER2(+) breast cancer, cannot block ligand-induced HER2 heterodimers, suggesting it cannot effectively inhibit HER2 signaling. Hence, HER2 oligomeric states may predict the odds of a clinical response to trastuzumab in HER2-driven tumors. To test this hypothesis, we generated nontransformed human MCF10A mammary epithelial cells stably expressing a chimeric HER2-FKBP molecule that could be conditionally induced to homodimerize by adding the FKBP ligand AP1510, or instead induced to heterodimerize with EGFR or HER3 by adding the heterodimer ligands EGF/TGFα or heregulin. AP1510, EGF, and heregulin each induced growth of MCF10A cells expressing HER2-FKBP. Trastuzumab inhibited homodimer-mediated but not heterodimer-mediated cell growth. In contrast, the HER2 antibody pertuzumab, which blocks HER2 heterodimerization, inhibited growth induced by heregulin but not AP1510. Lastly, the HER2/EGFR tyrosine kinase inhibitor lapatinib blocked both homodimer- and heterodimer-induced growth. AP1510 triggered phosphorylation of Erk1/2 but not AKT, whereas trastuzumab inhibited AP1510-induced Erk1/2 phosphorylation and Shc-HER2 homodimer binding, but not TGFα-induced AKT phosphorylation. Consistent with these observations, high levels of HER2 homodimers correlated with longer time to progression following trastuzumab therapy in a cohort of patients with HER2-overexpressing breast cancer. Together, our findings confirm the notion that HER2 oligomeric states regulate HER2 signaling, also arguing that trastuzumab sensitivity of homodimers may reflect their inability to activate the PI3K (phosphoinositide 3-kinase)/AKT pathway. A clinical implication of our results is that high levels of HER2 homodimers may predict a positive response to trastuzumab.

Quantitation of p95HER2 in Paraffin Sections by Using a p95-Specific Antibody and Correlation with Outcome in a Cohort of Trastuzumab-Treated Breast Cancer Patients

Purpose: p95HER2 is an NH2-terminally truncated form of HER2 that lacks the trastuzumab binding site and is therefore thought to confer resistance to trastuzumab treatment. In this report, we introduce a new antibody that has enabled the first direct quantitative measurement of p95HER2 in formalin-fixed paraffin-embedded (FFPE) breast cancer tissues. We sought to show that quantitative p95HER2 levels would correlate with outcome in trastuzumab-treated HER2-positive metastatic breast cancer. Experimental Design: The novel p95HER2 antibody used here was characterized for sensitivity, specificity, and selectivity over full-length HER2. Quantitative p95HER2 levels were measured in 93 metastatic breast tumors using a VeraTag FFPE assay to determine the correlation of p95HER2 levels with outcomes. Results: Within a cohort of trastuzumab-treated metastatic breast cancer patients, high levels of p95HER2 were found to correlate with shorter progression-free survival [hazard ratio (HR), 1.9; P = 0.017] and overall survival (HR, 2.2; P = 0.012) in patients with tumors selected to be HER2 positive by the VeraTag HER2 assay. For those with tumors found to be fluorescence in situ hybridization positive, elevated p95HER2 correlated similarly with shorter progression-free survival (HR, 1.8; P = 0.022) and overall survival (HR, 2.2; P = 0.009). Conclusions: We have successfully generated an antibody that can specifically detect p95HER2, and developed an assay to quantify expression in FFPE tumor specimens. Using this novel assay, we have identified a group of HER2-positive patients expressing p95HER2 that have a worse outcome while on trastuzumab. As p95HER2 retains sensitivity to kinase inhibitors, measurement of p95HER2 in breast tumor sections may be useful in guiding treatment for patients with HER2-positive breast cancer. Clin Cancer Res; 16(16); 4226–35. ©2010 AACR.

A novel proximity assay for the detection of proteins and protein complexes: quantitation of HER1 and HER2 total protein expression and homodimerization in formalin-fixed, paraffin-embedded cell lines and breast cancer tissue.

The availability of drugs targeting the EGFR/HER/erbB signaling pathway has created a need for diagnostics that accurately predict treatment responses. We have developed and characterized a novel assay to provide sensitive and quantitative measures of HER proteins and homodimers in formalin-fixed, paraffin-embedded (FFPE) cell lines and breast tumor tissues, to test these variables. In the VeraTag assay, HER proteins and homodimers are detected through the release of fluorescent tags conjugated to specific HER antibodies, requiring proximity to a second HER antibody. HER2 protein quantification was normalized to tumor area, and compared to receptor numbers in 12 human tumor cell lines determined by fluorescence-activated cell sorting (FACS), and with HER immunohistochemistry (IHC) test categories and histoscores in cell lines and 170 breast tumors. HER1 and HER2 expression levels determined by the VeraTag assay are proportional to receptor number over more than a 2 log10 range, and HER homodimer levels are consistent with crosslinking and immunoprecipitation results. VeraTag HER2 measurements of breast tumor tissue and cell lines correlate with standard IHC test categories (P<0.001). VeraTag HER2 levels also agree with IHC histoscores at lower HER2 protein levels, but are continuous and overlapping between IHC test categories, extending the dynamic range 5-fold to 10-fold at higher HER2 levels. The VeraTag assay specifically and reproducibly measures HER1 and HER2 protein and homodimers in FFPE tissues. The continuous measure of HER2 protein levels over a broad dynamic range, and the novel HER2 homodimer measure, are presently being assessed as predictive markers for responses to targeted HER2 therapy.

Anti-tumor effect of CT-322 as an Adnectin inhibitor of vascular endothelial growth factor receptor-2

CT-322 is a new anti-angiogenic therapeutic agent based on an engineered variant of the tenth type III domain of human fibronectin, i.e., an AdnectinTM, designed to inhibit vascular endothelial growth factor receptor (VEGFR)-2. This PEGylated Adnectin was developed using an mRNA display technology. CT-322 bound human VEGFR-2 with high affinity (KD, 11 nM), but did not bind VEGFR-1 or VEGFR-3 at concentrations up to 100 nM, as determined by surface plasmon resonance studies. Western blot analysis showed that CT-322 blocked VEGF-induced phosphorylation of VEGFR-2 and mitogen-activated protein kinase in human umbilical vascular endothelial cells. CT-322 significantly inhibited the growth of human tumor xenograft models of colon carcinoma and glioblastoma at doses of 15-60 mg/kg administered 3 times/week. Anti-tumor effects of CT-322 were comparable to those of sorafenib or sunitinib, which inhibit multiple kinases, in a colon carcinoma xenograft model, although CT-322 caused less overt adverse effects than the kinase inhibitors. CT-322 also enhanced the anti-tumor activity of the chemotherapeutic agent temsirolimus in the colon carcinoma model. The high affinity and specificity of CT-322 binding to VEGFR-2 and its anti-tumor activities establish CT-322 as a promising anti-angiogenic therapeutic agent. Our results further suggest that Adnectins are an important new class of targeted biologics that can be developed as potential treatments for a wide variety of diseases.

Quantitation of HER2 expression or HER2:HER2 dimers and differential survival in a cohort of metastatic breast cancer patients carefully selected for trastuzumab treatment primarily by FISH.

The selection of patients with HER2-positive breast cancer for treatment with trastuzumab is based on the measurement of HER2 protein expression by immunohistochemistry, or the presence of HER2 gene amplification by fluorescence in situ hybridization (FISH). By using multivariate analyses, we investigate the relationship between quantitative measurements of HER2 expression or HER2:HER2 dimers and objective response (Response Evaluation Criteria in Solid Tumors), time to progression, and breast cancer survival after trastuzumab treatment in a cohort of patients with metastatic breast cancer who were primarily selected for treatment by FISH. The VeraTag assay, a proximity-based assay designed to quantitate protein expression and dimerization in formalin-fixed, paraffin-embedded tissue specimens, was used to measure HER2 protein expression and HER2:HER2 dimer levels. In a Cox proportional hazards analysis, higher HER2 expression or HER2:HER2 dimer levels were both correlated with longer survival (P=0.0058 and P=0.016, respectively) after treatment with trastuzumab in a population of patients that were either FISH-positive (90%) or immunohistochemistry 3+ (10%). Patients with higher levels of HER2 expression or HER2:HER2 dimers seemed to derive little benefit from the addition of concomitant chemotherapy to trastuzumab, whereas those with lower levels benefited significantly [interaction test P=0.43 (HER2 expression), P=0.27 (HER2:HER2 dimers)]. These data suggest that more quantitative or functional measurements of HER2 status may facilitate the development of more personalized treatment strategies for patients with metastatic breast cancer.

Quantitative HER2 protein levels predict outcome in fluorescence in situ hybridization‐positive patients with metastatic breast cancer treated with trastuzumab

Only a portion of breast cancer patients currently selected for trastuzumab therapy respond.

High HER2 Expression Correlates with Response to the Combination of Lapatinib and Trastuzumab

Purpose: Expression of p95HER2 has been associated with resistance to trastuzumab-based therapy in patients with metastatic breast cancer. Conversely, high levels of HER2 have been linked with increased clinical benefit from anti-HER2 therapy. In this work, we aimed to investigate whether the levels of p95HER2 and HER2 can predict response to anti-HER2 therapy in patients with breast cancer. Experimental Design: We measured p95HER2 and HER2 by VeraTag and HERmark, respectively, in primary tumors of patients enrolled in the neoadjuvant phase III study NeoALTTO and correlated these variables with pathologic complete response (pCR) and progression-free survival (PFS) following lapatinib (L), trastuzumab (T), or the combination of both agents (L+T). Results: A positive correlation between p95HER2 and HER2 levels was found in the 274 cases (60%) in which quantification of both markers was possible. High levels of these markers were predictive for pCR, especially in the hormone receptor (HR)–positive subset of patients. High HER2 expression was associated with increased pCR rate upon L+T irrespective of the HR status. To examine whether the levels of either p95HER2 or HER2 could predict for PFS in patients treated with lapatinib, trastuzumab or L+T, we fit to the PFS data in Cox models containing log2(p95HER2) or log2(HER2). Both variables correlated with longer PFS. Conclusions: Increasing HER2 protein expression correlated with increased benefit of adding lapatinib to trastuzumab. HER2 expression is a stronger predictor of pCR and PFS than p95HER2 for response to lapatinib, trastuzumab and, more significantly, L+T. Clin Cancer Res; 21(3); 569–76. ©2014 AACR.

HER3, p95HER2, and HER2 protein expression levels define multiple subtypes of HER2-positive metastatic breast cancer.

Trastuzumab is effective in the treatment of HER2/neu over-expressing breast cancer, but not all patients benefit from it. In vitro data suggest a role for HER3 in the initiation of signaling activity involving the AKT–mTOR pathway leading to trastuzumab insensitivity. We sought to investigate the potential of HER3 alone and in the context of p95HER2 (p95), a trastuzumab resistance marker, as biomarkers of trastuzumab escape. Using the VeraTag® assay platform, we developed a dual antibody proximity-based assay for the precise quantitation of HER3 total protein (H3T) from formalin-fixed paraffin-embedded (FFPE) breast tumors. We then measured H3T in 89 patients with metastatic breast cancer treated with trastuzumab-based therapy, and correlated the results with progression-free survival and overall survival using Kaplan–Meier and decision tree analyses that also included HER2 total (H2T) and p95 expression levels. Within the sub-population of patients that over-expressed HER2, high levels of HER3 and/or p95 protein expression were significantly associated with poor clinical outcomes on trastuzumab-based therapy. Based on quantitative H3T, p95, and H2T measurements, multiple subtypes of HER2-positive breast cancer were identified that differ in their outcome following trastuzumab therapy. These data suggest that HER3 and p95 are informative biomarkers of clinical outcomes on trastuzumab therapy, and that multiple subtypes of HER2-positive breast cancer may be defined by quantitative measurements of H3T, p95, and H2T.

Correlation Between Quantitative HER-2 Protein Expression and Risk for Brain Metastases in HER-2+ Advanced Breast Cancer Patients Receiving Trastuzumab-Containing Therapy

BACKGROUND Patients with human epidermal growth factor receptor (HER)-2+ breast cancer are at particularly high risk for brain metastases; however, the biological basis is not fully understood. Using a novel HER-2 assay, we investigated the correlation between quantitative HER-2 expression in primary breast cancers and the time to brain metastasis (TTBM) in HER-2+ advanced breast cancer patients treated with trastuzumab. METHODS The study group included 142 consecutive patients who were administered trastuzumab-based therapy for HER-2+ metastatic breast cancer. HER-2/neu gene copy number was quantified as the HER-2/centromeric probe for chromosome 17 (CEP17) ratio by central laboratory fluorescence in situ hybridization (FISH). HER-2 protein was quantified as total HER-2 protein expression (H2T) by the HERmark® assay (Monogram Biosciences, Inc., South San Francisco, CA) in formalin-fixed, paraffin-embedded tumor samples. HER-2 variables were correlated with clinical features and TTBM was measured from the initiation of trastuzumab-containing therapy. RESULTS A higher H2T level (continuous variable) was correlated with shorter TTBM, whereas HER-2 amplification by FISH and a continuous HER-2/CEP17 ratio were not predictive (p = .013, .28, and .25, respectively). In the subset of patients that was centrally determined by FISH to be HER-2+, an above-the-median H2T level was significantly associated with a shorter TTBM (hazard ratio, [HR], 2.4; p = .005), whereas this was not true for the median HER-2/CEP17 ratio by FISH (p = .4). Correlation between a continuous H2T level and TTBM was confirmed on multivariate analysis (HR, 3.3; p = .024). CONCLUSIONS These data reveal a strong relationship between the quantitative HER-2 protein expression level and the risk for brain relapse in HER-2+ advanced breast cancer patients. Consequently, quantitative assessment of HER-2 protein expression may inform and facilitate refinements in therapeutic treatment strategies for selected subpopulations of patients in this group.

Potential biomarkers of long-term benefit from single-agent trastuzumab or lapatinib in HER2-positive metastatic breast cancer

In 2009 a prospective, randomized Phase II trial (NCT00842998) was initiated to evaluate the activity of HER2‐targeting agents without chemotherapy (CT) in HER2‐positive metastatic breast cancer (MBC) patients. The primary tumors of the patients enrolled in this study offered a unique opportunity to identify biomarkers that could predict durable clinical benefit from CT‐free anti‐HER2 therapy.