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Next-generation Trop-2–targeted therapy against advanced cancers is hampered by expression of Trop-2 in normal tissues. We discovered that Trop-2 undergoes proteolytic activation by ADAM10 in cancer cells, leading to the exposure of a previously inaccessible protein groove flanked by two N-glycosylation sites. We designed a recognition strategy for this region, to drive selective cancer vulnerability in patients. Most undiscriminating anti–Trop-2 mAbs recognize a single immunodominant epitope. Hence, we removed it by deletion mutagenesis. Cancer-specific, glycosylation-prone mAbs were selected by ELISA, bio-layer interferometry, flow cytometry, confocal microscopy for differential binding to cleaved/activated, wild-type and glycosylation site–mutagenized Trop-2. The resulting 2G10 mAb family binds Trop-2–expressing cancer cells, but not Trop-2 on normal cells. We humanized 2G10 by state-of-the-art complementarity determining region grafting/re-modeling, yielding Hu2G10. This antibody binds cancer-specific, cleaved/activated Trop-2 with Kd < 10−12 mol/L, and uncleaved/wtTrop-2 in normal cells with Kd 3.16×10−8 mol/L, thus promising an unprecedented therapeutic index in patients. In vivo, Hu2G10 ablates growth of Trop-2–expressing breast, colon, prostate cancers, but shows no evidence of systemic toxicity, paving the way for a paradigm shift in Trop-2–targeted therapy.

We recently reported that activation of Trop-2 through its cleavage at R87-T88 by ADAMIO underlies Trop-2-driven progression of colon cancer. However, the mechanism of action and pathological impact of Trop-2 in metastatic diffusion remain unexplored. Through searches for molecular determinants of cancer metastasis, we identified TROP2 as unique in its up-regulation across independent colon cancer metastasis models. Overexpression of wild-type Trop-2 in KM12SM human colon cancer cells increased liver metastasis rates in vivo in immunosuppressed mice. Metastatic growth was further enhanced by a tail-less, activated Delta cytoTrop-2 mutant, indicating the Trop-2 tail as a pivotal inhibitory signaling element. In primary tumors and metastases, transcriptome analysis showed no down-regulation of CDH1 by transcription factors for epithelial-to-mesenchymal transition, thus suggesting that the pro-metastatic activity of Trop-2 is through alternative mechanisms. Trop-2 can tightly interact with ADAM10. Here, Trop-2 bound E-cadherin and stimulated ADAM10-mediated proteolytic cleavage of E-cadherin intracellular domain. This induced detachment of E-cadherin from beta-actin, and loss of cell-cell adhesion, acquisition of invasive capability, and membrane-driven activation of beta-catenin signaling, which were further enhanced by the Delta cytoTrop-2 mutant. This Trop-2/E-cadherin/beta-catenin program led to anti-apoptotic signaling, increased cell migration, and enhanced cancer-cell survival. In patients with colon cancer, activation of this Trop-2-centered program led to significantly reduced relapse-free and overall survival, indicating a major impact on progression to metastatic disease. Recently, the anti-Trop-2 mAb Sacituzumab govitecan-hziy was shown to be active against metastatic breast cancer. Our findings define the key relevance of Trop-2 as a target in metastatic colon cancer. Funding Agencies|grants of Fondazione of the Cassa di Risparmio della Provincia di Chieti; Compagnia di San PaoloCompagnia di San Paolo [2489IT]; Italian Ministry of Development [MI01_00424]; Region Abruzzo (POR FESR) [C78C14000100005]; Oncoxx Biotech (Italian Ministry of University and Research, Smart Cities and Communities) [SCN_00558]; Programma Per Giovani Ricercatori "Rita Levi Montalcini", Italian Ministry of University and Research [PGR12I7N1Z]

Purpose: Inhibition of AKT is a key target area for personalized cancer medicine. However, predictive markers of response to AKT inhibitors are lacking. Correspondingly, the AKT-dependent chain of command for tumor growth, which will mediate AKT-dependent therapeutic responses, remains unclear. Experimental Design: Proteomic profiling was utilized to identify nodal hubs of the Trop-2 cancer growth–driving network. Kinase-specific inhibitors were used to dissect Trop-2–dependent from Trop-2–independent pathways. In vitro assays, in vivo preclinical models, and case series of primary human breast cancers were utilized to define the mechanisms of Trop-2–driven growth and the mode of action of Trop-2–predicted AKT inhibitors. Results: Trop-2 and AKT expression was shown to be tightly coordinated in human breast cancers, with virtual overlap with AKT activation profiles at T308 and S473, consistent with functional interaction in vivo. AKT allosteric inhibitors were shown to only block the growth of Trop-2–expressing tumor cells, both in vitro and in preclinical models, being ineffective on Trop-2–null cells. Consistently, AKT-targeted siRNA only impacted on Trop-2–expressing cells. Lentiviral downregulation of endogenous Trop-2 abolished tumor response to AKT blockade, indicating Trop-2 as a mandatory activator of AKT. Conclusions: Our findings indicate that the expression of Trop-2 is a stringent predictor of tumor response to AKT inhibitors. They also support the identification of target-activatory pathways, as efficient predictors of response in precision cancer therapy. Clin Cancer Res; 22(16); 4197–205. ©2016 AACR.