Phosphorylated epidermal growth factor receptor on tumor-associated endothelial cells in human renal cell carcinoma is a primary target for therapy by tyrosine kinase inhibitors

A Novel HER2 Protein Identification Methodology in Breast Cancer Cells Using Raman Spectroscopy and Raman Imaging: An Analytical Validation Study

Conventional assays such as immunohistochemistry (IHC) and in situ hybridization (ISH) used in clinical procedures for quantification of the human epidermal growth factor receptor-2 (HER2) status in breast cancer have many limitations. In the current study, we have used HER2 expression in a broad range of breast cancer phenotypes to explore the potential utility of a novel immunodetection technique using Raman spectroscopy and Raman imaging combined with artificial intelligence models. The correlations between the Raman method and conventional HER2 testing methodologies (IHC and ISH) have been tested. Raman measurements showed a strong linear correlation (p = 0.05, R2=0,9816) with IHC analysis in the studied breast cell lines: MCF-10A, MCF-7, MDA-MB-231, HTB-30 (SK-BR-3), and AU-565 represent normal, nontumorigenic epithelial cells, triple-positive breast carcinoma, and triple-negative breast cancer cell lines. Analytic testing of Raman spectroscopy and Raman imaging demonstrated that this method may offer advantages over the currently used diagnostic methodologies.

Altered proTGFα/cleaved TGFα ratios offer new therapeutic strategies in renal carcinoma

BACKGROUND

Treatment of renal cancer has significantly improved with the arrival to the clinic of kinase inhibitors and immunotherapies. However, the disease is still incurable in advanced stages. The fact that several approved inhibitors for kidney cancer target receptor tyrosine kinases (RTKs) suggests that these proteins play a critical role in the pathophysiology of the disease. Based on these precedents, we decided to explore whether RTKs other than those targeted by approved drugs, contribute to the development of kidney cancer.

METHODS

The activation status of 49 RTKs in 44 paired samples of normal and tumor kidney tissue was explored using antibody arrays, with validation by western blotting. Genetic and pharmacologic approaches were followed to study the biological implications of targeting the epidermal growth factor receptor (EGFR) and its ligand Transforming Growth Factor-α (TGFα).

RESULTS

Activation of the EGFR was found in a substantial number of tumors. Moreover, kidney tumors expressed elevated levels of TGFα. Down-regulation of EGFR or TGFα using RNAi or their pharmacological targeting with blocking antibodies resulted in inhibition of the proliferation of in vitro cellular models of renal cancer. Importantly, differences in the molecular forms of TGFα expressed by tumors and normal tissues were found. In fact, tumor TGFα was membrane anchored, while that expressed by normal kidney tissue was proteolytically processed.

CONCLUSIONS

The EGFR-TGFα axis plays a relevant role in the pathophysiology of kidney cancer. This study unveils a distinctive feature in renal cell carcinomas, which is the presence of membrane-anchored TGFα. That characteristic could be exploited therapeutically to act on tumors expressing transmembrane TGFα, for example, with antibody drug conjugates that could recognize the extracellular region of that protein.

Sprouting strategies and dead ends in anti-angiogenic targeting of NETs

Neuroendocrine tumors (NETs) are a heterogeneous group of neoplasms that arise from cells of the neuroendocrine system. NETs are characterized by being highly vascularized tumors that produce large amounts of proangiogenic factors. Due to their complexity and heterogeneity, progress in the development of successful therapeutic approaches has been limited. For instance, standard chemotherapy-based therapies have proven to be poorly selective for tumor cells and toxic for normal tissues. Considering the urge to develop an efficient therapy to treat NET patients, vascular targeting has been proposed as a new approach to block tumor growth. This review provides an update of the mechanisms regulating different components of vessels and their contribution to tumor progression in order to develop new therapeutic drugs. Following the description of classical anti-angiogenic therapies that target VEGF pathway, new angiogenic targets such as PDGFs, EGFs, FGFs and semaphorins are further explored. Based on recent research in the field, the combination of therapies that target multiple and different components of vessel formation would be the best approach to specifically target NETs and inhibit tumor growth.

Erlotinib Pretreatment Improves Photodynamic Therapy of Non-Small Cell Lung Carcinoma Xenografts via Multiple Mechanisms

Aberrant expression of the epidermal growth factor receptor (EGFR) is a common characteristic of many cancers, including non-small cell lung carcinoma (NSCLC), head and neck squamous cell carcinoma, and ovarian cancer. Although EGFR is currently a favorite molecular target for the treatment of these cancers, inhibition of the receptor with small-molecule inhibitors (i.e., erlotinib) or monoclonal antibodies (i.e., cetuximab) does not provide long-term therapeutic benefit as standalone treatment. Interestingly, we have found that addition of erlotinib to photodynamic therapy (PDT) can improve treatment response in typically erlotinib-resistant NSCLC tumor xenografts. Ninety-day complete response rates of 63% are achieved when erlotinib is administered in three doses before PDT of H460 human tumor xenografts, compared with 16% after PDT-alone. Similar benefit is found when erlotinib is added to PDT of A549 NCSLC xenografts. Improved response is accompanied by increased vascular shutdown, and erlotinib increases the in vitro cytotoxicity of PDT to endothelial cells. Tumor uptake of the photosensitizer (benzoporphyrin derivative monoacid ring A; BPD) is increased by the in vivo administration of erlotinib; nevertheless, this elevation of BPD levels only partially accounts for the benefit of erlotinib to PDT. Thus, pretreatment with erlotinib augments multiple mechanisms of PDT effect that collectively lead to large improvements in therapeutic efficacy. These data demonstrate that short-duration administration of erlotinib before PDT can greatly improve the responsiveness of even erlotinib-resistant tumors to treatment. Results will inform clinical investigation of EGFR-targeting therapeutics in conjunction with PDT.

Higher circulating expression levels of miR-221 associated with poor overall survival in renal cell carcinoma patients

The mechanisms involved in renal cell carcinoma (RCC) development and progression remain unclear, and new biomarkers for early detection, follow-up of the disease and prognosis are needed in routine practice to improve the diagnostic and/or prognostic accuracy. There is increasing evidence that microRNAs (miRNAs) are involved in cancer development and progression. The up-regulation of miR-221/222 has been described in several human cancers, and during RCC development, this up-regulation can modulate the metastatic process. Our purpose was to investigate the circulating expression levels of miR-221/222 as potential biomarkers for RCC detection and their influence in patients' overall survival. The circulating miR-221/222 was studied by relative quantification in 77 plasma samples. A follow-up study was undertaken to evaluate the overall survival. We observed that RCC patients presented higher circulating expression levels of miR-221 and miR-222 than healthy individuals (2(-ΔΔCt) = 2.8, P = 0.028; 2(-ΔΔCt) = 2.2, P = 0.044, respectively). The RCC patients with metastasis at diagnosis also presented higher circulating expression levels of miR-221 than patients with no metastasis (2(-ΔΔCt) = 10.9, P = 0.001). We also observed a significantly lower overall survival in patients with higher expression levels of miR-221 (48 vs 116 months, respectively; P = 0.024). Furthermore, multivariate Cox regression analysis using the tumour, nodes and metastasis stage (TNM stage); Fuhrman nuclear grade and age (≥60 years) as covariants demonstrated a higher risk of specific death by cancer in patients who presented higher expression levels of miR-221 (hazard ratio (HR) = 10.7, 95% confidence interval 1.33-85.65, P = 0.026). The concordance (c) index showed that the definition of profiles that contain information regarding tumour characteristics associated with circulating miR-221 expression information presents an increased capacity to predict the risk of death by RCC (c index model 1, 0.800 vs model 2, 0.961). Our results, which identified the plasma miR-221/222 at variable levels during RCC development, suggest that these miRNAs may have a potential as noninvasive biomarkers of RCC development.

Signaling of ERBB receptor tyrosine kinases promotes neuroblastoma growth in vitro and in vivo

BACKGROUND

ERBB receptor tyrosine kinases can mediate proliferation, migration, adhesion, differentiation, and survival in many types of cells and play critical roles in many malignancies. Recent reports suggest a role for EGFR signaling in proliferation and survival of neuroblastoma, a common form of pediatric cancer that often has an extremely poor outcome.

METHODS

The authors examined ERBB family expression in neuroblastoma cell lines and patient samples by flow cytometry, western blot, and quantitative real time polymerase chain reaction (Q-PCR). Response to ERBB inhibition was assessed in vitro by cell-cycle analysis and western blot and in vivo by serial tumor-size measurements.

RESULTS

A panel of neuroblastoma cell lines and primary patient tumors expressed EGFR, HER-3, and HER-4, with HER-2 in some tumors. HER-4 mRNA was expressed predominantly in cleavable isoforms. Whereas EGFR inhibition with erlotinib and pan-ERBB inhibition with CI-1033 inhibited EGF-induced phosphorylation of EGFR, AKT, and ERK1/2, only CI-1033 induced growth inhibition and dose-dependent apoptosis in vitro. Both CI-1033 and erlotinib treatment of neuroblastoma xenograft tumors resulted in decreased tumor growth in vivo, although CI-1033 was more effective. In vivo expression of EGFR was observed predominantly in vascular endothelial cells.

CONCLUSIONS

Pan-ERBB inhibition is required for ERBB-related neuroblastoma apoptosis in vitro, although EGFR contributes indirectly to tumor growth in vivo. Inhibition of EGFR in endothelial cells may be an important aspect of erlotinib's impact on neuroblastoma growth in vivo. Our results suggest that non-EGFR ERBB family members contribute directly to neuroblastoma growth and survival, and pan-ERBB inhibition represents a potential therapeutic target for treating neuroblastoma.

Combined vascular endothelial growth factor receptor and epidermal growth factor receptor (EGFR) blockade inhibits tumor growth in xenograft models of EGFR inhibitor resistance

PURPOSE

The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) gefitinib and erlotinib benefit some non-small cell lung cancer (NSCLC) patients, but most do not respond (primary resistance) and those who initially respond eventually progress (acquired resistance). EGFR TKI resistance is not completely understood and has been associated with certain EGFR and K-RAS mutations and MET amplification.

EXPERIMENTAL DESIGN

We hypothesized that dual inhibition of the vascular endothelial growth factor (VEGF) and EGFR pathways may overcome primary and acquired resistance. We investigated the VEGF receptor/EGFR TKI vandetanib, and the combination of bevacizumab and erlotinib in vivo using xenograft models of EGFR TKI sensitivity, primary resistance, and three models of acquired resistance, including models with mutated K-RAS and secondary EGFR T790M mutation.

RESULTS

Vandetanib, gefitinib, and erlotinib had similar profiles of in vitro activity and caused sustained tumor regressions in vivo in the sensitive HCC827 model. In all four resistant models, vandetanib and bevacizumab/erlotinib were significantly more effective than erlotinib or gefitinib alone. Erlotinib resistance was associated with a rise in both host and tumor-derived VEGF but not EGFR secondary mutations in the KRAS mutant-bearing A549 xenografts. Dual inhibition reduced tumor endothelial proliferation compared with VEGF or EGFR blockade alone, suggesting that the enhanced activity of dual inhibition is due at least in part to antiendothelial effects.

CONCLUSION

These studies suggest that erlotinib resistance may be associated with a rise in both tumor cell and host stromal VEGF and that combined blockade of the VEGFR and EGFR pathways can abrogate primary or acquired resistance to EGFR TKIs. This approach merits further evaluation in NSCLC patients.

Neoplasia: the second decade

This issue marks the end of the 10-year anniversary of Neoplasia where we have seen exciting growth in both number of submitted and published articles in Neoplasia. Neoplasia was first published in 1999. During the past 10 years, Neoplasia has dynamically adapted to the needs of the cancer research community as technologies have advanced. Neoplasia is currently providing access to articles through PubMed Central to continue to facilitate rapid broad-based dissemination of published findings to the scientific community through an Open Access model. This has in part helped Neoplasia to achieve an improved impact factor this past year, demonstrating that the manuscripts published by Neoplasia are of great interest to the overall cancer research community. This past year, Neoplasia received a record number of articles for review and has had a 21% increase in the number of published articles.

The interaction of radiation therapy and antiangiogenic therapy

Since its beginning in the early 1970s, the field of angiogenesis research has grown rapidly and it has now become apparent that the endothelial cell is a critical regulator of the malignant phenotype. Multiple antiangiogenic agents have now been used in the clinic yet a better understanding of the process of angiogenesis is still needed before these agents can be successfully incorporated into clinical practice. Although antiangiogenic agents offer great therapeutic potential, preclinical and clinical studies suggest that these agents will have a delayed onset of activity and may only induce disease stabilization for patients with advanced malignancy. The use of radiation therapy for cancer is also associated with therapeutic challenges that are distinct from those that might be expected with antiangiogenic agents. Thus, the use of angiogenesis inhibitors in combination with radiation therapy should help to overcome the limitations of each leading to enhanced efficacy and diminished toxicity. The goal of this review is to provide an update of ongoing progress and current challenges related to the use of angiogenesis inhibitors with radiation therapy.

Phosphorylated epidermal growth factor receptor on tumor-associated endothelial cells is a primary target for therapy with tyrosine kinase inhibitors

We determined whether phosphorylated epidermal growth factor receptor (EGFR) expressed on tumor-associated endothelial cells is a primary target for therapy with EGFR tyrosine kinase inhibitors (TKIs). Human colon cancer cells SW620CE2 (parental) that do not express EGFR or human epidermal growth factor receptor 2 (HER2) but express transforming growth factor alpha (TGF-alpha) were transduced with a lentivirus carrying nontargeting small hairpin RNA (shRNA) or TGF-alpha shRNA. The cell lines were implanted into the cecum of nude mice. Two weeks later, treatment began with saline, 4-[R]-phenethylamino-6-[hydroxyl] phenyl-7H-pyrrolo [2,3-D]-pyrimidine (PKI166), or irinotecan. Endothelial cells in parental and nontargeting shRNA tumors expressed phosphorylated EGFR. Therapy with PKI166 alone or with irinotecan produced apoptosis of these endothelial cells and necrosis of the EGFR-negative tumors. Endothelial cells in tumors that did not express TGF-alpha did not express EGFR, and these tumors were resistant to treatment with PKI166. The response of neoplasms to EGFR antagonists has been correlated with EGFR mutations, HER2 expression, Akt activation, and EGFR gene copy number. Our present data using colon cancer cells that do not express EGFR or HER2 suggest that the expression of TGF-alpha by tumor cells leading to the activation of EGFR in tumor-associated endothelial cells is a major determinant for the susceptibility of neoplasms to therapy by specific EGFR-TKI.

Targeting EGFR activity in blood vessels is sufficient to inhibit tumor growth and is accompanied by an increase in VEGFR-2 dependence in tumor endothelial cells

Epidermal growth factor receptor (EGFR) targeting agents such as kinase inhibitors reduce tumor growth and progression. We have previously reported that EGFR is not only expressed by the tumor cells but by the tumor endothelial cells (EC) as well (Amin, D. N., Hida, K., Bielenberg, D. R., Klagsbrun, M., 2006. Tumor endothelial cells express epidermal growth factor receptor (EGFR) but not ErbB3 and are responsive to EGF and to EGFR kinase inhibitors. Cancer Res. 66, 2173-80). Thus, targeting tumor blood vessel EGFR may be a viable strategy for tumor growth inhibition. We describe here a melanoma xenograft model where the tumor cells express very little or no EGFR but the tumor blood vessels express activated EGFR. The EGFR kinase inhibitor, gefitinib (Iressa), retarded tumor growth with a size decrease of 38% compared to control mice, ostensibly due to targeting of the blood vessels. EC were isolated from tumors of gefitinib-treated mice. These EC were unable to proliferate in response to EGF and displayed relatively weaker activation of MAPK and AKT signaling in response to EGF compared to tumor EC isolated from vehicle-treated mice. In contrast, the tumor EC from gefitinib-treated mice expressed higher levels of VEGFR-2 both at the mRNA and protein level. In addition, these cells were less sensitive to EGFR kinase inhibitors in vitro but more sensitive to a VEGFR-2 kinase inhibitor. These results suggest that in tumor EC from gefitinib-treated mice there is a switch from dependence on EGFR activity to signaling via VEGFR-2. Our data provide a molecular rationale for combination therapies targeting both EGF and VEGF signaling on the tumor vasculature.

Inhibition of epidermal growth factor receptor and vascular endothelial growth factor receptor phosphorylation on tumor-associated endothelial cells leads to treatment of orthotopic human colon cancer in nude mice

The purpose of our study was to determine whether the dual inhibition of epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor (VEGFR) signaling pathways in tumor-associated endothelial cells can inhibit the progressive growth of human colon carcinoma in the cecum of nude mice. SW620CE2 human colon cancer cells growing in culture and orthotopically in the cecum of nude mice expressed a high level of transforming growth factor alpha (TGF-alpha) and vascular endothelial growth factor (VEGF) but were negative for EGFR, human epidermal growth factor receptor 2 (HER2), and VEGFR. Double immunofluorescence staining revealed that tumor-associated endothelial cells expressed EGFR, VEGFR2, phosphorylated EGFR (pEGFR), and phosphorylated VEGFR (pVEGFR). Treatment of mice with either 7H-pyrrolo [2,3-d]-pyrimidine lead scaffold (AEE788; an inhibitor of EGFR and VEGFR tyrosine kinase) or CPT-11 as single agents significantly inhibited the growth of cecal tumors (P < .01); this decrease was even more pronounced with AEE788 combined with CPT-11 (P < .001). AEE788 alone or combined with CPT-11 also inhibited the expression of pEGFR and pVEGFR on tumor-associated endothelial cells, significantly decreased vascularization and tumor cell proliferation, and increased the level of apoptosis in both tumor-associated endothelial cells and tumor cells. These data demonstrate that targeting EGFR and VEGFR signaling on tumor-associated endothelial cells provides a viable approach for the treatment of colon cancer.

The role of the EGFR signaling in tumor microenvironment

The epidermal growth factor receptor (EGFR) family comprehends four different tyrosine kinases (EGFR, ErbB-2, ErbB-3, and ErbB-4) that are activated following binding to epidermal growth factor (EGF)-like growth factors. It has been long established that the EGFR system is involved in tumorigenesis. These proteins are frequently expressed in human carcinomas and support proliferation and survival of cancer cells. However, activation of the EGFR in non-malignant cell populations of the neoplastic microenvironment might also play an important role in cancer progression. EGFR signaling regulates in tumor cells the synthesis and secretion of several different angiogenic growth factors, including vascular endothelial growth factor (VEGF), interleukin-8 (IL-8), and basic fibroblast growth factor (bFGF). Overexpression of ErbB-2 also leads to increased expression of angiogenic growth factors, whereas treatment with anti-EGFR or anti-ErbB-2 agents produces a significant reduction of the synthesis of these proteins by cancer cells. EGFR expression and function in tumor-associated endothelial cells has also been described. Therefore, EGFR signaling might regulate angiogenesis both directly and indirectly. In addition, activation of EGFR is involved in the pathogenesis of bone metastases. Within the bone marrow microenvironment, cancer cells stimulate the synthesis of osteoclastogenic factors by residing stromal cells, a phenomenon that leads to bone destruction. It has been shown that EGFR signaling regulates the ability of bone marrow stromal cells to produce osteoclastogenic factors and to sustain osteoclast activation. Taken together, these findings suggest that the EGFR system is an important mediator, within the tumor microenvironment, of autocrine and paracrine circuits that result in enhanced tumor growth.

Expression of epidermal growth factor (EGF)/transforming growth factor-alpha by human lung cancer cells determines their response to EGF receptor tyrosine kinase inhibition in the lungs of mice

Epidermal growth factor receptor (EGFR) has been extensively targeted in the treatment of non-small cell lung cancer, producing responses in a small number of patients. To study the role of ligand expression in mediating response to EGFR antagonism, we injected NCI-H441 [EGFR and EGF/transforming growth factor-alpha (TGF-alpha) positive] or PC14-PE6 (EGFR positive and EGF/TGF-alpha negative) human lung adenocarcinoma cells into the lungs of nude mice. We randomized the mice to receive treatment with the EGFR tyrosine kinase inhibitors gefitinib or AEE788 or vehicle. Treatment of mice bearing NCI-H441 but not PC14-PE6 lung tumors resulted in a significant reduction in primary tumor growth, pleural effusion, and lymph node metastasis. Immunohistochemical analyses revealed that NCI-H441 and PC14-PE6 cells expressed EGFR but that the expression of EGF/TGF-alpha was high in NCI-H441 cells and very low in PC14-PE6 cells. Consequently, EGFR was activated in both tumor and tumor-associated endothelial cells in the NCI-H441 tumors but not in the PC14-PE6 tumors. Antagonism of EGFR signaling by treatment of mice with AEE788 decreased proliferation and increased apoptosis of both tumor cells and tumor-associated endothelial cells in NCI-H441 tumors but not in PC14-PE6 tumors. However, after transfection of PC14-PE6 cells with TGF-alpha, lung tumors derived from the transfected cells expressed and activated EGFR in both tumor and tumor-associated endothelial cells and tumors responded to treatment with AEE788. Collectively, these results strongly suggest that the response of human lung cancers growing orthotopically in mice to the inhibition of EGFR signaling is determined by ligand (EGF/TGF-alpha) expression by tumor cells. Our findings provide an additional explanation for the susceptibility of lung cancers to treatment with EGFR tyrosine kinase inhibitors.

Species differences in renal Src activity direct EGF receptor regulation in life or death response to EGF

In rodent models of obstructive nephropathy, exogenous epidermal growth factor (EGF) attenuates tubule cell death in rats and exacerbates cell death in mice. To identify species differences in EGF receptor (EGFR) regulation and signaling, cell lysates were prepared from rat, mouse, and human proximal tubule cells (PTC) and compared by immunoblot analysis for expression and phosphorylation of Src and EGFR. Frozen kidney tissue was also analyzed. Results indicate mouse PTC have constitutive Src- and EGFR-kinase activities not detected in rat or human PTC. Immunoblots of rat, mouse, and human kidney homogenates confirmed this finding in vivo. Src-specific inhibitor PP2 and EGFR kinase inhibitor AG1478 decreased EGF-induced apoptosis in mouse PTC by 74% (P < 0.001) and 70% (P < 0.001), respectively. Expression of a constitutive Src mutant cDNA in rat PTC rendered cells susceptible to EGF-induced death. EGF decreased stretch-induced apoptosis by 66% (P < 0.001) relative to vehicle control in human PTC, similar to rat PTC response. We conclude that elevated Src activity in mouse tubular cells alters downstream EGFR signaling and increases susceptibility to EGF-induced cell death. The unexpected finding that a therapeutic agent (EGF) in rats is detrimental in mice underscores the importance of determining which animal best represents the response of human kidneys to a given agent.