Purpose: KRAS mutations confer adverse prognosis to colorectal cancer, and no targeted therapies have shown efficacy in this patient subset. Paracrine, nongenetic events induced by KRAS-mutant tumor cells are expected to result in specific deregulation and/or relocation of tumor microenvironment (TME) proteins, which in principle can be exploited as alternative therapeutic targets. Experimental Design: A multimodal strategy combining ex vivo/in vitro phage display screens with deep-sequencing and bioinformatics was applied to uncover TME-specific targets in KRAS-mutant hepatic metastasis from colorectal cancer. Expression and localization of BCAM and LAMA5 were validated by immunohistochemistry in preclinical models of human hepatic metastasis and in a panel of human specimens (n ¼ 71). The antimetastatic efficacy of two BCAM-mimic peptides was evaluated in mouse models. The role of BCAM in the interaction of KRAS-mutant colo-rectal cancer cells with TME cells was investigated by adhesion assays. Results: BCAM and LAMA5 were identified as molecular targets within both tumor cells and TME of KRAS-mutant hepatic metastasis from colorectal cancer, where they were specifically overexpressed. Two BCAM-mimic peptides inhibited KRAS-mutant hepatic metastasis in preclinical models. Genetic suppression and biochemical inhibition of either BCAM or LAMA5 impaired adhesion of KRAS-mutant colorectal cancer cells specifically to endothelial cells, whereas adhesion to pericytes and hepatocytes was unaffected. Conclusions: These data show that the BCAM/LAMA5 system plays a functional role in the metastatic spreading of KRASmutant colorectal cancer by mediating tumor-TME interactions and as such represents a valuable therapeutic candidate for this large, currently untreatable patient group. Clin Cancer Res; 22(19); 4923-33. Ó2016 AACR.

Homing of colorectal cancer (CRC) cells to the liver is a non-random process driven by a crosstalk between tumour cells and components of the host tissue. Here we report the isolation of a liver metastasis-specific peptide ligand (CGIYRLRSC) that binds a complex of E-cadherin and α6 integrin on the surface of CRC cells. We identify angiopoietin-like 6 protein as a peptide-mimicked natural ligand enriched in hepatic blood vessels of CRC patients. We demonstrate that an interaction between hepatic angiopoietin-like 6 and tumoural α6 integrin/E-cadherin drives liver homing and colonization by CRC cells, and that CGIYRLRSC inhibits liver metastasis through interference with this ligand/receptor system. Our results indicate a mechanism for metastasis whereby a soluble factor accumulated in normal vessels functions as a specific ligand for circulating cancer cells. Consistently, we show that high amounts of coexpressed α6 integrin and E-cadherin in primary tumours represent a poor prognostic factor for patients with advanced CRC.

Edited by Hans-Dieter KlenkKeywords: HIV-1 gp120 Tat Virus entry Peptide a b s t r a c t Preventing cell entry of human immunodeficiency virus 1 (HIV-1) is of interest for the development of innovative therapies. We previously reported a specific interaction between HIV-1 envelope glycoprotein 120 (gp120) and Tat at the cell surface, which enhances virus attachment and entry. We also identified a gp120-mimicking peptide, CT319, that competes with gp120 for Tat binding, thus inhibiting HIV-1 infection. Here we report a molecular dissection of gp120 regions involved in this mechanism. Our findings identify the V1/V2 loop of gp120 as involved in Tat binding, and define this interaction as functionally relevant for HIV-1 entry into host cells. Structured digital abstract:Tat physically interacts with gp120 by pull down (1,2,3,4)

The introduction of biodrugs, e.g. the anti-EGFR antibodies, was initially seen as a promise to radically change the landscape for patients with metastatic colorectal cancer. However, although EGFR-targeted therapies, combined with chemotherapy, have prolonged survival expectancy to 24 months, cure remains anecdotal. Target therapies suffer of high costs, important side effects, and low response rates: it is now clear that this approach as it was originally conceived failed to meet the majority of its expectations. Importantly, because of novel prescription guidelines, patients with KRAS-mutated tumors are excluded from EGFR-targeted therapies: for these patients alternative treatments are urgently needed. We here propose an innovative strategy based on the identification of molecular targets specifically associated with the microenvironment of metastatic colorectal cancer in patients carrying oncogenic KRAS. For this purpose, we set up mice models of metastatic colorectal cancer by intrasplenic (to evaluate liver homing) and intrahepatic (to investigate liver colonization) implantation of human colorectal cancer cell lines (SW48 and LIM1215) in which oncogenic KRAS (G12D, G12V, G13D) variants have been somatically knocked-in. We based our “target fishing” strategy on high-throughput, phage display-mediated proteomic screenings of deriving tumor samples ex vivo. Proteome signatures from the cognate cell lines in vitro served as a subtractive reference for the ex vivo biopanning, aimed at the identification of peptide ligands specific for non-epithelial components. By this combined biological-genetic-bioinformatics approach, we identified peptide/protein signatures selectively associated to metastasis microenvironments with controlled genetic backgrounds in vitro and in vivo. We selected 2 target proteins and 2 targeting peptides, which were exploited for diagnostic and therapeutic purposes. First, we evaluated by IHC the presence and localization of the target proteins in samples (tumor, healthy liver) from a panel of human biopsies and from the described in vivo models. This analysis confirmed a specific enrichment in KRAS-mutated microenvironments. Second, we tested the capability of dye-conjugated targeting peptides to home to these same tumor microenvironments, observing a specific accumulation in target tissues, compared to their scrambled versions and to control tissues. Third, we investigated a potential anti-metastatic effect of these peptides when orthotopically co-injected with colorectal cancer cell lines; preliminary experiments revealed that the targeting peptides, but not the scrambled variants, inhibit the onset of liver metastases from KRAS-mutated cell lines. In summary, we obtained proof-of-concept results in preclinical studies and produced prototype compounds to provide innovative tools that can be translated into the clinical practice with a mid-term perspective. Citation Format: Serena Marchio, Alice Bartolini, Sabrina Cardaci, Marco Soster, Giorgio Corti, Simona Lamba, Federico Bussolino, Davide Cora', Federica Di Nicolantonio. Microenvironment targets in KRAS-mutated metastatic colorectal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1163. doi:10.1158/1538-7445.AM2014-1163