Trastuzumab Sensitizes Ovarian Cancer Cells to EGFR-targeted Therapeutics

<p>Abstract</p> <p>Background</p> <p>Early studies have demonstrated comparable levels of HER2/ErbB2 expression in both breast and ovarian cancer. Trastuzumab (Herceptin), a therapeutic monoclonal antibody directed against HER2, is FDA-approved for the treatment of both early and late stage breast cancer. However, clinical studies of trastuzumab in epithelial ovarian cancer (EOC) patients have not met the same level of success. Surprisingly, however, no reports have examined either the basis for primary trastuzumab resistance in ovarian cancer or potential ways of salvaging trastuzumab as a potential ovarian cancer therapeutic.</p> <p>Methods</p> <p>An in vitro model of primary trastuzumab-resistant ovarian cancer was created by long-term culture of HER2-positive ovarian carcinoma-derived cell lines with trastuzumab. Trastuzumab treated vs. untreated parental cells were compared for HER receptor expression, trastuzumab sensitivity, and sensitivity to other HER-targeted therapeutics.</p> <p>Results</p> <p>In contrast to widely held assumptions, here we show that ovarian cancer cells that are not growth inhibited by trastuzumab are still responsive to trastuzumab. Specifically, we show that responsiveness to alternative HER-targeted inhibitors, such as gefitinib and cetuximab, is dramatically potentiated by long-term trastuzumab treatment of ovarian cancer cells. HER2-positive ovarian carcinoma-derived cells are, therefore, not "unresponsive" to trastuzumab as previously assumed, even when they not growth inhibited by this drug.</p> <p>Conclusions</p> <p>Given the recent success of EGFR-targeted therapeutics for the treatment of other solid tumors, and the well-established safety profile of trastuzumab, results presented here provide a rationale for re-evaluation of trastuzumab as an experimental ovarian cancer therapeutic, either in concert with, or perhaps as a "primer" for EGFR-targeted therapeutics.</p

Transient anabolic effects accompany epidermal growth factor receptor signal activation in articular cartilage in vivo

INTRODUCTION: Signals from the epidermal growth factor receptor (EGFR) have typically been considered to provide catabolic activities in articular cartilage, and accordingly have been suggested to have a causal role in osteoarthritis progression. The aim of this study was to determine in vivo roles for endogenous EGFR signal activation in articular cartilage. METHODS: Transgenic mice with conditional, limb-targeted deletion of the endogenous intracellular EGFR inhibitor Mig-6 were generated using CreLoxP (Mig-6-flox; Prx1Cre) recombination. Histology, histochemical staining and immunohistochemistry were used to confirm activation of EGFR signaling in the articular cartilage and joints, and to analyze phenotypic consequences of Mig-6 loss on articular cartilage morphology, proliferation, expression of progenitor cell markers, presence of chondrocyte hypertrophy and degradation of articular cartilage matrix. RESULTS: The articular cartilage of Mig-6-conditional knockout (Mig-6-cko) mice was dramatically and significantly thicker than normal articular cartilage at 6 and 12 weeks of age. Mig-6-cko articular cartilage contained a population of chondrocytes in which EGFR signaling was activated, and which were three to four times more proliferative than normal Mig-6-flox articular chondrocytes. These cells expressed high levels of the master chondrogenic regulatory factor Sox9, as well as high levels of putative progenitor cell markers including superficial zone protein (SZP), growth and differentiation factor-5 (GDF-5) and Notch1. Expression levels were also high for activated β-catenin and the transforming growth factor beta (TGF-β) mediators phospho-Smad2/3 (pSmad2/3). Anabolic effects of EGFR activation in articular cartilage were followed by catabolic events, including matrix degradation, as determined by accumulation of aggrecan cleavage fragments, and onset of hypertrophy as determined by type × collagen expression. By 16 weeks of age, the articular cartilage of Mig-6-cko knees was no longer thickened and was degenerating. CONCLUSIONS: These results demonstrate unexpected anabolic effects of EGFR signal activation in articular cartilage, and suggest the hypothesis that these effects may promote the expansion and/or activity of an endogenous EGFR-responsive cell population within the articular cartilage

EGFR isoforms and gene regulation in human endometrial cancer cells

BACKGROUND: Epidermal growth factor (EGF) and its receptor (EGFR) constitute a principal growth-promoting pathway in endometrial cancer cells. Pre-clinical studies were undertaken to compare the expression of EGFR isoforms and the downstream effects of activating or blocking EGFR function in Ishikawa H cells, derived from a moderately differentiated type I endometrioid adenocarcinoma, or in Hec50co cells, derived from a poorly differentiated type II adenocarcinoma with papillary serous sub-differentiation. RESULTS: We investigated whether EGFR mutations are present in the tyrosine kinase domain (exons 18-22) of EGFR and also whether EGFR isoforms are expressed in the Ishikawa H or Hec50co cell lines. Sequence of the EGFR tyrosine kinase domain proved to be wild type in both cell lines. While both cell lines expressed full-length EGFR (isoform A), EGFR and sEGFR (isoform D) were expressed at significantly lower levels in Hec50co cells compared to Ishikawa H cells. Analysis of gene expression following EGF vs. gefitinib treatment (a small molecule EGFR tyrosine kinase inhibitor) was performed. Early growth response 1, sphingosine kinase 2, dual specificity phosphatase 6, and glucocorticoid receptor DNA binding factor 1 are members of a cluster of genes downstream of EGFR that are differentially regulated by treatment with EGF compared to gefitinib in Ishikawa H cells, but not in Hec50co cells. CONCLUSIONS: Type I Ishikawa H and type II Hec50co endometrial carcinoma cells both express EGFR and sEGFR, but differ markedly in their responsiveness to the EGFR inhibitor gefitinib. This difference is paralleled by differences in the expression of sEGFR and EGFR, as well as in their transcriptional response following treatment with either EGF or gefitinib. The small cluster of differently regulated genes reported here in these type I vs. type II endometrial cancer-derived cell lines may identify candidate biomarkers useful for predicting sensitivity to EGFR blockade

GT198 Expression Defines Mutant Tumor Stroma in Human Breast Cancer

Human breast cancer precursor cells remain to be elucidated. Using breast cancer gene product GT198 (PSMC3IP; alias TBPIP or Hop2) as a unique marker, we revealed the cellular identities of GT198 mutant cells in human breast tumor stroma. GT198 is a steroid hormone receptor coactivator and a crucial factor in DNA repair. Germline mutations in GT198 are present in breast and ovarian cancer families. Somatic mutations in GT198 are present in ovarian tumor stromal cells. Herein, we show that human breast tumor stromal cells carry GT198 somatic mutations and express cytoplasmic GT198 protein. GT198(+) stromal cells share vascular smooth muscle cell origin, including myoepithelial cells, adipocytes, capillary pericytes, and stromal fibroblasts. Frequent GT198 mutations are associated with GT198(+) tumor stroma but not with GT198(-) tumor cells. GT198(+) progenitor cells are mostly capillary pericytes. When tested in cultured cells, mutant GT198 induces vascular endothelial growth factor promoter, and potentially promotes angiogenesis and adipogenesis. Our results suggest that multiple lineages of breast tumor stromal cells are mutated in GT198. These findings imply the presence of mutant progenitors, whereas their descendants, carrying the same GT198 mutations, are collectively responsible for forming breast tumor microenvironment. GT198 expression is, therefore, a specific marker of mutant breast tumor stroma and has the potential to facilitate diagnosis and targeted treatment of human breast cancer

Soluble Human Epidermal Growth Factor Receptor 2 (sHER2) as a Potential Risk Assessment, Screening, and Diagnostic Biomarker of Lung Adenocarcinoma

Lung cancer is the leading cause of cancer-related death in the United States. Here, we evaluated the potential clinical utility of soluble human epidermal growth factor receptor 2 (sHER2) for the risk assessment, screening, and diagnosis of non-small cell lung cancer (NSCLC) using an unmatched case-control study design. Serum sHER2 concentrations were measured by immunoassay in 244 primary NSCLC cases and 218 healthy controls. Wilcoxon rank-sum tests, logistic regression models, and receiver operating characteristic plots were used to assess whether sHER2 is associated with lung cancer. Median serum sHER2 concentrations are higher in patients with adenocarcinoma than squamous cell carcinoma regardless of gender, and sHER2 is a weak, independent biomarker of adenocarcinoma, but not of squamous cell carcinoma, adjusted for age and gender. The age-adjusted relative risk (odds) of adenocarcinoma is 3.95 (95% CI: 1.22, 12.81) and 7.93 (95% CI: 2.26, 27.82) greater for women and men with high sHER2 concentrations (≥ 6.60 ng/mL) vs. low sHER2 concentrations (≤ 1.85 ng/mL), respectively. When adjusted for each other, sHER2, age, and gender discern healthy controls from patients with primary adenocarcinomas of the lung with 85.9% accuracy. We conclude that even though serum sHER2 is not a strong, stand-alone discriminatory biomarker of adenocarcinoma, sHER2 may be a useful, independent covariate in multivariate risk assessment, screening, and diagnostic models of lung cancer

Neratinib overcomes trastuzumab resistance in HER2 amplified breast cancer.

Trastuzumab has been shown to improve the survival outcomes of HER2 positive breast cancer patients. However, a significant proportion of HER2-positive patients are either inherently resistant or develop resistance to trastuzumab. We assessed the effects of neratinib, an irreversible panHER inhibitor, in a panel of 36 breast cancer cell lines. We further assessed its effects with or without trastuzumab in several sensitive and resistant breast cancer cells as well as a BT474 xenograft model. We confirmed that neratinib was significantly more active in HER2-amplified than HER2 non-amplified cell lines. Neratinib decreased the activation of the 4 HER receptors and inhibited downstream pathways. However, HER3 and Akt were reactivated at 24 hours, which was prevented by the combination of trastuzumab and neratinib. Neratinib also decreased pHER2 and pHER3 in acquired trastuzumab resistant cells. Neratinib in combination with trastuzumab had a greater growth inhibitory effect than either drug alone in 4 HER2 positive cell lines. Furthermore, trastuzumab in combination with neratinib was growth inhibitory in SKBR3 and BT474 cells which had acquired resistance to trastuzumab as well as in a BT474 xenograft model. Innately trastuzumab resistant cell lines showed sensitivity to neratinib, but the combination did not enhance response compared to neratinib alone. Levels of HER2 and phospho-HER2 showed a direct correlation with sensitivity to neratinib. Our data indicate that neratinib is an effective anti-HER2 therapy and counteracted both innate and acquired trastuzumab resistance in HER2 positive breast cancer. Our results suggest that combined treatment with trastuzumab and neratinib is likely to be more effective than either treatment alone for both trastuzumab-sensitive breast cancer as well as HER2-positive tumors with acquired resistance to trastuzumab

Lin28 Regulates BMP4 and Functions with Oct4 to Affect Ovarian Tumor Microenvironment

Emerging evidence suggests that the tumor microenvironment plays a critical role in regulating cancer stem cells (CSCs) and tumor progression through both autocrine and paracrine signaling. Elevated production of bone morphogenetic proteins (BMPs) from human ovarian cancer cells and stroma has been shown to increase CSC proliferation and tumor growth. Here, we report that Lin28, a stem cell factor, binds to BMP4 mRNA in epithelial ovarian carcinoma cells thereby promoting BMP4 expression at the posttranscriptional level. As co-expression of Lin28 and Oct4 (another stem cell factor) has been implicated in ovarian cancer CSCs, we also determined that high levels of Lin28 are associated with an unfavorable prognosis when co-expressed with high levels of Oct4. Together, these findings uncover a new level of regulation of BMP4 expression, and imply a novel Lin28/Oct4/BMP4-mediated mechanism of regulating ovarian tumor cell growth, thus holding potential for the development of new strategies for the diagnosis and treatment of ovarian cancer.This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Landes Bioscience and can be found at: http://www.landesbioscience.com/journals/cc/.Keywords: Ovarian cancer, Posttranscriptional, BMP4, Tumor microenvironment, Lin28/Oct

Id-1 stimulates cell proliferation through activation of EGFR in ovarian cancer cells

Increased EGFR (epidermal growth factor receptor) expression has been reported in many types of human cancer and its levels are positively associated with advanced cancers. Recently, upregulation of Id-1 (inhibitor of differentiation or DNA binding) protein was found in over 70% of ovarian cancer samples and correlated with poor survival of ovarian cancer patients. However, the molecular mechanisms responsible for the role of Id-1 in ovarian cancer are not clear. The aim of this study was to investigate the effect of Id-1 on ovarian cancer proliferation and its association with the EGFR pathway. To achieve this, we transfected an Id-1 expression vector into three ovarian cancer cell lines and examined cell proliferation rate by flow cytometry and bromodeoxyuridine staining. We found that ectopic Id-1 expression led to increased cell proliferation demonstrated by increased BrdU incorporation rate and S-phase fraction. The Id-1-induced cell growth was associated with upregulation of EGFR at both transcriptional and protein levels. In contrast, inactivation of Id-1 through transfection of an Id-1 antisense vector resulted in downregulation of EGFR. Our results indicate that increased Id-1 in ovarian cancer cells may promote cancer cell proliferation through upregulation of EGFR. Our findings also implicate that Id-1 may be a potential target for the development of novel strategies in the treatment of ovarian cancer. © 2004 Cancer Research UK.link_to_OA_fulltex