Samer-ul Haque

Endothelin-1 stimulates colon cancer adjacent fibroblasts.

Endothelin‐1 (ET‐1) is produced by and stimulates colorectal cancer cells. Fibroblasts produce tumour stroma required for cancer development. We investigated whether ET‐1 stimulated processes involved in tumour stroma production by colonic fibroblasts. Primary human fibroblasts, isolated from normal tissues adjacent to colon cancers, were cultured with or without ET‐1 and its antagonists. Cellular proliferation, migration and contraction were measured. Expression of enzymes involved in tumour stroma development and alterations in gene transcription were determined by Western blotting and genome microarrays. ET‐1 stimulated proliferation, contraction and migration (p < 0.01 v control) and the expression of matrix degrading enzymes TIMP‐1 and MMP‐2, but not MMP‐3. ET‐1 upregulated genes for profibrotic growth factors and receptors, signalling molecules, actin modulators and extracellular matrix components. ET‐1 stimulated colonic fibroblast cellular processes in vitro that are involved in developing tumour stroma. Upregulated genes were consistent with these processes. By acting as a strong stimulus for tumour stroma creation, ET‐1 is proposed as a target for adjuvant cancer therapy.

Endothelin receptor antagonism and cancer

The endothelin peptides have an important role in the cancer‐stromal interactions that promote tumour growth. Endothelin‐1 (ET‐1), clinically the most investigated endothelin, is a vital agent in the growth and progression of several tumours including prostate, ovarian, colorectal, bladder, breast and lung carcinomas. ET‐1 exerts its effects through the activation of two distinct receptors, ETA and ETB. Once activated, these receptors transmit signals via numerous intracellular signalling pathways. The effects of ET receptor stimulation in cancer cells or cancer‐associated cells include proliferation, resistance to apoptosis, angiogenesis, migration and subsequent invasion. At present, the manipulation of the endothelin axis within the pre‐clinical setting is the subject of intense investigation. Recent studies into ET receptor antagonism have produced interesting results highlighting the fact that these receptors may provide novel targets for a new generation of chemotherapeutic agents in a variety of cancers.

Efficacy of the Specific Endothelin A Receptor Antagonist Zibotentan (ZD4054) in Colorectal Cancer: A Preclinical Study

Endothelin 1 (ET-1) is overexpressed in cancer, contributing to disease progression. We previously showed that ET-1 stimulated proliferative, migratory, and contractile tumorigenic effects via the ETA receptor. Here, for the first time, we evaluate zibotentan, a specific ETA receptor antagonist, in the setting of colorectal cancer, in cellular models. Pharmacologic characteristics were further determined in patient tissues. Colorectal cancer lines (n = 4) and fibroblast strains (n = 6), isolated from uninvolved areas of colorectal cancer specimens, were exposed to ET-1 and/or ETA/B receptor antagonists. Proliferation (methylene blue), migration (scratch wounds), and contraction (gel lattices) were assessed. Receptor distribution and binding characteristics (Kd, Bmax) were determined using autoradiography on tissue sections and homogenates and cytospun cells, supported by immunohistochemistry. Proliferation was inhibited by ETA (zibotentan > BQ123; P < 0.05), migration by ETB > ETA, and contraction by combined ETA and ETB antagonism. Intense ET-1 stromal binding correlated with fibroblasts and endothelial cells. Colorectal cancer lines and fibroblasts revealed high density and affinity ET-1 binding (Bmax = 2.435 fmol/1 × 106 cells, Kd = 367.7 pmol/L; Bmax = 3.03 fmol/1 × 106 cells, Kd = 213.6 pmol/L). In cancer tissues, ETA receptor antagonists (zibotentan; BQ123) reduced ET-1 binding more effectively (IC50: 0.1–10 μmol/L) than ETB receptor antagonist BQ788 (∼IC50, 1 mmol/L). ET-1 stimulated cancer-contributory processes. Its localization to tumor stroma, with greatest binding/affinity to fibroblasts, implicates these cells in tumor progression. ETA receptor upregulation in cancer tissues and its role in tumorigenic processes show the receptors importance in therapeutic targeting. Zibotentan, the most specific ETA receptor antagonist available, showed the greatest inhibition of ET-1 binding. With its known safety profile, we provide evidence for zibotentans potential role as adjuvant therapy in colorectal cancer. Mol Cancer Ther; 12(8); 1556–67. ©2013 AACR.

Biologics against cancer-specific receptors - challenges to personalised medicine from early trial results.

Understanding molecular mechanisms of tumourigenesis underlies new therapeutic strategies that specifically target tumours. This has led to the evolution of personalised therapy that was first used in breast cancer when hormone receptor status was determined. More recently in colorectal cancer treatment the Epidermal Growth Factor receptor and its tumourigenic role has led to its targeting by using Cetuximab and Panitumumab. Addition of these drugs to existing drug regimes (FOLFOX and FOLFIRI) showed improved respectability rates in patients with liver metastasis. Most recently the Endothelin receptor has been implicated in multiple tumourigenic processes. Interest has grown in using Endothelin A receptor antagonists as adjuvant or combination therapy as suggested by the FOLFERA and FOLFIRI trials currently on-going.

Efficacy of zibotentan in colorectal cancer--response.

Panagiotis Vlachostergios highlights the importance of evaluating clinically the targeted therapeutic zibotentan. Despite the wide overexpression of endothelin-1 (ET-1) and endothelin A receptors in the majority of carcinomas ([1][1]), establishing clinical efficacy of receptor antagonism has

Abstract B190: Efficacy of the specific ETA receptor antagonist zibotentan (ZD4054) in cancer cells and fibroblasts from colorectal cancer

Endothelin‐1 (ET‐1) contributes to growth and progression of solid cancers, mainly through endothelin receptor A (ETAR). Therefore endothelin receptor antagonism is emerging as a potential treatment for neoplasms. We evaluated the efficacy of the specific ETAR antagonist zibotentan (ZD4054) in blocking ET‐driven cellular effects in colorectal cancer (CRC). CRC cell lines (HT29, SW620) and primary normal fibroblast strains isolated from human colorectal tissues (CF36, CF56, CF65, CF75) were incubated in ET‐1 with/without BQ123, zibotentan (ETAR antagonists), BQ788 (ETBR antagonist). Resultant cell growth was measured by the colourimetric methylene blue assay; migration by a modified monolayer scratch assay; contraction in collagen gels; downstream effectors by western blotting. ET‐1 driven growth (18%–45% above control) was significantly inhibited (p BQ123; CRC and fibroblasts); (2) collagen XI was blocked by ETAR>ETBR antagonism (zibotentan>BQ123; fibroblasts). The specific ETAR antagonist zibotentan is at least as efficacious as BQ123 in blocking ET‐1 driven growth, migration and contraction both in CRC cells and colorectal fibroblasts, which form the supporting tumor stroma. Zibotentan is a strong candidate for adjuvant treatment in CRC. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B190.