Supplementary Materials and Methods; Supplementary Tables S1-S4.

Aims: Neuropilin-2 is a coreceptor for vascular endothelial growth factor family members. Blockade of neuropilin-2 is able to suppress lymphogenous metastasis in preclinical models. The aim of this study was to validate a protocol for the evaluation of neuropilin-2 protein expression in situ, by comparison with in-situ hybridization, western blotting, and mRNA expression levels. Methods and results: Immunohistochemistry was performed on normal human tissues, and whole sections for 79 primary non-small-cell lung carcinomas, 65 primary breast carcinomas, 79 primary colorectal cancers, and 52 metastases. Neuropilin-2 expression was observed in lymphatic and blood vessels from all normal and malignant tissues examined. In addition, 32% of primary non-small-cell lung carcinomas, 15% of primary breast carcinomas and 22% of primary colorectal cancers showed tumour cell expression. Fifty-five primary and nine secondary malignant melanomas were also examined for neuropilin-2 expression by in-situ hybridization. All showed vascular expression, and 85% of primary malignant melanomas showed tumour cell expression. Conclusions: In the majority of lung, breast and colorectal cancers, the effects of anti-neuropilin-2 are likely to be restricted to the vasculature. These results will assist in pharmacokinetic evaluations, tolerability assessments and the choice of setting to evaluate the activity of anti-neuropilin-2 therapies.

Hedgehog (Hh) signaling is critical to the patterning and development of a variety of organ systems, and both ligand-dependent and ligand-independent Hh pathway activation are known to promote tumorigenesis. Recent studies have shown that in tumors promoted by Hh ligands, activation occurs within the stromal microenvironment. Testing whether ligand-driven Hh signaling promotes tumor angiogenesis, we found that Hh antagonism reduced the vascular density of Hh-producing LS180 and SW480 xenografts. In addition, ectopic expression of sonic hedgehog in low-Hh-expressing DLD-1 xenografts increased tumor vascular density, augmented angiogenesis, and was associated with canonical Hh signaling within perivascular tumor stromal cells. To better understand the molecular mechanisms underlying Hh-mediated tumor angiogenesis, we established an Hh-sensitive angiogenesis coculture assay and found that fibroblast cell lines derived from a variety of human tissues were Hh responsive and promoted angiogenesis in vitro through a secreted paracrine signal(s). Affymetrix array analyses of cultured fibroblasts identified VEGF-A, hepatocyte growth factor, and PDGF-C as candidate secreted proangiogenic factors induced by Hh stimulation. Expression studies of xenografts and angiogenesis assays using combinations of Hh and VEGF-A inhibitors showed that it is primarily Hh-induced VEGF-A that promotes angiogenesis in vitro and augments tumor-derived VEGF to promote angiogenesis in vivo.

Abstract Purpose: Inappropriate activation of the Hedgehog (Hh) signaling pathway in skin is critical for the development of basal cell carcinomas (BCC). We have investigated the anti-BCC efficacy of topically-applied CUR61414, an inhibitor of the Hh signal transduction molecule Smoothened. Experimental Design: In preclinical studies, we used a depilatory model to evaluate the ability of topical formulations of CUR61414 to repress Hh responsive cells found at the base of hair follicles in normal skin. We also tested the in vivo effects of topical CUR61414 on murine BCCs developed in Ptch1 +/− K14-CreER2 p53 fl/fl mice. In a phase I clinical study, we evaluated the safety, tolerability, and efficacy of a multidose regimen of CUR61414 (0.09%, 0.35%, 1.1%, and 3.1%) applied topically to human superficial or nodular BCCs for up to 28 days. Results: In mice, topical CUR61414 significantly inhibited skin Hh signaling, blocked the induction of hair follicle anagen, and shrank existing BCCs. However, we observed no clinical activity of this formulation in human superficial or nodular BCCs in a phase I clinical study. Conclusions: Our data highlight some of the challenges of translating preclinical experience into successful human results for a topical anticancer agent. Clin Cancer Res; 17(10); 3378–87. ©2011 AACR.

The four receptors of the Notch family are widely expressed transmembrane proteins through which mammalian cells communicate to regulate cell fate and growth. Defects in Notch signalling are linked to many cancers, including acute lymphoblastic leukaemia. Using phage display technology, a multi-department team at Genentech has produced synthetic antibodies that act as potent and specific antagonists of Notch1 and Notch2. Anti-Notch1 shows antitumour activity in pre-clinical mouse models, inhibiting both cancer cell growth and angiogenesis, and is active against human cancer cells in culture. Inhibition of Notch1 and 2 together causes intestinal toxicity, whereas inhibition of each singly largely avoids this effect, a potential therapeutic advantage over 'pan-Notch' inhibitors. The four receptors of the Notch family are transmembrane proteins through which mammalian cells communicate to regulate cell fate and growth. Aberrant signalling through each receptor has been linked to disease, so the Notch pathway is a compelling drug target. But current drugs cannot distinguish between the different Notch proteins. Here, phage display technology has been used to generate highly specialized antibodies, enabling the functions of Notch1 and Notch2 to be discriminated in humans and mice. The four receptors of the Notch family are widely expressed transmembrane proteins that function as key conduits through which mammalian cells communicate to regulate cell fate and growth1,2. Ligand binding triggers a conformational change in the receptor negative regulatory region (NRR) that enables ADAM protease cleavage3,4 at a juxtamembrane site that otherwise lies buried within the quiescent NRR5,6. Subsequent intramembrane proteolysis catalysed by the γ-secretase complex liberates the intracellular domain (ICD) to initiate the downstream Notch transcriptional program. Aberrant signalling through each receptor has been linked to numerous diseases, particularly cancer7, making the Notch pathway a compelling target for new drugs. Although γ-secretase inhibitors (GSIs) have progressed into the clinic8, GSIs fail to distinguish individual Notch receptors, inhibit other signalling pathways9 and cause intestinal toxicity10, attributed to dual inhibition of Notch1 and 2 (ref. 11). To elucidate the discrete functions of Notch1 and Notch2 and develop clinically relevant inhibitors that reduce intestinal toxicity, we used phage display technology to generate highly specialized antibodies that specifically antagonize each receptor paralogue and yet cross-react with the human and mouse sequences, enabling the discrimination of Notch1 versus Notch2 function in human patients and rodent models. Our co-crystal structure shows that the inhibitory mechanism relies on stabilizing NRR quiescence. Selective blocking of Notch1 inhibits tumour growth in pre-clinical models through two mechanisms: inhibition of cancer cell growth and deregulation of angiogenesis. Whereas inhibition of Notch1 plus Notch2 causes severe intestinal toxicity, inhibition of either receptor alone reduces or avoids this effect, demonstrating a clear advantage over pan-Notch inhibitors. Our studies emphasize the value of paralogue-specific antagonists in dissecting the contributions of distinct Notch receptors to differentiation and disease and reveal the therapeutic promise in targeting Notch1 and Notch2 independently.

Arising from: J. Ridgway et al. Nature444, 1083–1087 (2006)10.1038/nature05313 Delta-like 4 (DLL4)-mediated Notch signalling has emerged as an attractive target for cancer therapy 1 , 2 . However, the potential side effects of blocking this pathway remain uncertain. Here we show that chronic DLL4 blockade causes pathological activation of endothelial cells, disrupts normal organ homeostasis and induces vascular tumours, raising important safety concerns.

The Hedgehog (Hh) signaling pathway is inappropriately activated in certain human cancers, including medulloblastoma, an aggressive brain tumor. GDC-0449, a drug that inhibits Hh signaling by targeting the serpentine receptor Smoothened (SMO), has produced promising anti-tumor responses in early clinical studies of cancers driven by mutations in this pathway. To evaluate the mechanism of resistance in a medulloblastoma patient who had relapsed after an initial response to GDC-0449, we determined the mutational status of Hh signaling genes in the tumor after disease progression. We identified an amino acid substitution at a conserved aspartic acid residue of SMO that had no effect on Hh signaling but disrupted the ability of GDC-0449 to bind SMO and suppress this pathway. A mutation altering the same amino acid also arose in a GDC-0449-resistant mouse model of medulloblastoma. These findings show that acquired mutations in a serpentine receptor with features of a G protein-coupled receptor can serve as a mechanism of drug resistance in human cancer.

Medulloblastoma is the most common malignant brain tumor in children. Aberrant activation of the hedgehog signaling pathway is strongly implicated in the development of some cases of medulloblastoma. A 26-year-old man with metastatic medulloblastoma that was refractory to multiple therapies was treated with a novel hedgehog pathway inhibitor, GDC-0449; treatment resulted in rapid (although transient) regression of the tumor and reduction of symptoms. Molecular analyses of tumor specimens obtained before treatment suggested that there was activation of the hedgehog pathway, with loss of heterozygosity and somatic mutation of the gene encoding patched homologue 1 (PTCH1), a key negative regulator of hedgehog signaling.

Abstract The Hedgehog (Hh) signaling pathway has been directly implicated in the pathogenesis of basal cell carcinoma (BCC) and medulloblastoma (MB). Constitutive Hh signaling, most often due to underlying loss of function mutations in the inhibitory receptor Patched1 (PTCH1), has been demonstrated in a majority of common localized BCCs and approximately 25–30% of sporadic MB cases. In this study, we examined molecular correlatives of clinical efficacy in locally-advanced / metastatic BCC and MB patients treated with GDC-0449, an inhibitor of the Hh pathway that targets the serpentine receptor Smoothened (SMO). An analysis of Hh pathway transcriptional target gene expression in archival tissue biopsies provided evidence for active Hh signaling in patients exhibiting clinical benefit (objective response or disease stabilization) on therapy. This was further supported by the identification of either loss of function or activating mutations in PTCH1 or SMO, respectively. We were unable to provide evidence for active Hh signaling in 2 patients with progressive disease as best response, potentially underlying the reason for lack of efficacy in these patients. In addition to providing molecular support for Hh pathway activity in patients exhibiting treatment benefit, this is the first evidence for Hh pathway dysregulation in the previously uncharacterized, advanced BCC setting. Furthermore, the results begin to support the utility of transcriptional-based tests as a strategy to potentially select the subset of MB patients with Hh-driven disease that would likely benefit on GDC-0449. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A44.

The Hedgehog (Hh) pathway has been implicated in pancreatic cancer but its role remains controversial. To delineate the cell populations able to respond to Hh ligand stimulation, we expressed an oncogenic allele of Smoothened (SmoM2) to cell autonomously activate Hh signaling in the mouse pancreas. Surprisingly, we found that expression of SmoM2 in epithelial cells was not able to activate the pathway and had no impact on pancreatic development or neoplasia. In contrast, activation of Smo in the mesenchyme led to Hh pathway activation, indicating that only the tumor stroma is competent to transduce the Hh signal. Using a Ptc-LacZ reporter mouse, we show that Hh signaling is active in stromal cells surrounding Hh-expressing tumor epithelium in various mouse pancreatic cancer models. Activation of the Hh pathway in the tumor stroma of human pancreatic and metastatic cancer specimens was confirmed by quantitative RT-PCR of microdissected tissue samples. These data support a paracrine model of Hh-mediated tumorigenesis, in which tumor cells secrete Hh ligand to induce tumor-promoting Hh target genes in adjacent stroma.

1621 Haploinsufficiency of Dll4, a vascular specific Notch ligand, underscores its essential role in embryonic vascular development and arteriogenesis. Mechanistically, it remains to be defined how the Dll4-mediated Notch pathway contributes to the complex vascular processes. We took advantage of a Dll4-selective antibody and found that neutralizing Dll4 rendered endothelial cells hyperproliferative, and caused defective cell fate specification /differentiation both in vitro and in vivo. Preferential expression of Dll4 in tumor vasculature as opposed to normal tissue vessels suggests its possible role in tumor angiogenesis, yet it is still speculative whether Dll4 is directly involved in tumor angiogenesis. In our study, blocking of Dll4 showed significant anti-tumor efficacy in tumor models. Remarkably, anti-Dll4 and anti-VEGF exhibited paradoxically distinct effects on tumor vasculature. Our data also supports the notion that Dll4-mediated Notch signaling is largely restricted to the vascular compartment. Therefore, targeting Dll4 may represent a broadly efficacious and well-tolerated approach for the treatment of solid tumors.

Blood line VEGF, or vascular endothelial growth factor, is the best-characterized inducer of tumour angiogenesis, and the blockade of VEGF has become an important tool in cancer therapy. But VEGF blockade is not effective against all tumours, so the search for alternative approaches continues. Two groups this week report that one such alternative could be blockade of Dll4, Delta-like ligand 4. This transmembrane molecule is part of the Notch signalling pathway. It was known to be essential for normal development of blood vessels in the embryo: the new work shows that it is also required for tumour angiogenesis. It may be a viable — and potentially well tolerated — alternative in patients with solid tumours that are resistant to anti-VEGF therapy.