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Trop-2 is a transmembrane signal transducer that can induce cancer growth. Using antibody targeting and N-terminal Edman degradation, we show here that Trop-2 undergoes cleavage in the first thyroglobulin domain loop of its extracellular region, between residues R87 and T88. Molecular modeling indicated that this cleavage induces a profound rearrangement of the Trop-2 structure, which suggested a deep impact on its biological function. No Trop-2 cleavage was detected in normal human tissues, whereas most tumors showed Trop-2 cleavage, including skin, ovary, colon, and breast cancers. Coimmunoprecipitation and mass spectrometry analysis revealed that ADAM10 physically interacts with Trop-2. Immunofluorescence/confocal time-lapse microscopy revealed that the two molecules broadly colocalize at the cell membrane. We show that ADAM10 inhibitors, siRNAs and shRNAs abolish the processing of Trop-2, which indicates that ADAM10 is an effector protease. Proteolysis of Trop-2 at R87-T88 triggered cancer cell growth both in vitro and in vivo. A corresponding role was shown for metastatic spreading of colon cancer, as the R87A-T88A Trop-2 mutant abolished xenotransplant metastatic dissemination. Activatory proteolysis of Trop-2 was recapitulated in primary human breast cancers. Together with the prognostic impact of Trop-2 and ADAM10 on cancers of the skin, ovary, colon, lung, and pancreas, these data indicate a driving role of this activatory cleavage of Trop-2 on malignant progression of tumors.

Nanoscopic, millisecond-lasting membrane platforms are modeled to constitute main functional signaling units. However, multiple signaling events in cell growth induction, including receptor Tyr-kinase (RTK) stimulation, calcium signaling, cytoplasmic kinase recruitment, operate over much broader space-time frames. Through dynamic confocal/super-resolution/electron-microscopy on living cells, we discovered that signaling competence is acquired through growth factor-induced coalescence of activated growth inducers (RTK, CD9, CD81, CD98, Co-029, CD316, Trop-1, Trop-2, PI3K, PI4K), and downstream effectors (Grb-2, PKCα, ERK, Akt, Src, Syk, ILK, ezrin) into confined segments of the cell membrane (‘docks’), that recursively assemble over hundreds of seconds. Average size (25±5 μm; ~80,000 individual analyses) and lifetime (222±25 sec) of docks extend by orders of magnitude previously recognized space-time frames for cell signaling. Activated/phosphorylated kinases clustered at membrane docks (99% P-Erb-B4; 91% P-Ret; 90% P-PKCα; 90% P-Src). STED super-resolution microscopy revealed up to 10 µm2 signal transducer areas of effector colocalization. Docks >1.0 µm2 accounted for ~90% of colocalizations versus ≈1% of raft-sized domains (HGF, IGF-1>>SCF/VEGF), were inhibited by Tyr kinase and cytoskeleton inhibitors, and were shown to induce cancer cell proliferation. Citation Format: Saverio Alberti, Valeria Relli, Romina Tripaldi, Pasquale Simeone, Emanuela Guerra, Andrea Sacchetti, Paolo Ciufici, Antonino Moschella, Valeria Caiolfa, Moreno Zamai, Marco Trerotola. Growth factor-induced cell membrane macroplatforms drive protein kinase signaling for transformed cell growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2550.

The recognition code between transcription factor (TF) amino acids and DNA bases remains poorly understood. Here, the determinants of TF amino acid-DNA base binding selectivity were identified through the analysis of crystals of TF-DNA complexes. Selective, high-frequency interactions were identified for the vast majority of amino acid side chains (‘structural code’). DNA binding specificities were then independently assessed by meta-analysis of random-mutagenesis studies of Zn finger-target DNA sequences. Selective, high-frequency interactions were identified for the majority of mutagenized residues (‘mutagenesis code’). The structural code and the mutagenesis code were shown to match to a striking level of accuracy (P = 3.1 × 10−33), suggesting the identification of fundamental rules of TF binding to DNA bases. Additional insight was gained by showing a geometry-dictated choice among DNA-binding TF residues with overlapping specificity. These findings indicate the existence of a DNA recognition mode whereby the physical-chemical characteristics of the interacting residues play a deterministic role. The discovery of this DNA recognition code advances our knowledge on fundamental features of regulation of gene expression and is expected to pave the way for integration with higher-order complexity approaches.

Trop-2 is a type I transmembrane glycoprotein, which is overexpressed in the majority of carcinomas, where it drives tumor cell proliferation. In its mature, glycosylated/functionally-competent form, Trop-2 associates with worse prognosis. A global quest was conducted for identifying decisive drivers of cancer metastasis. Cancer cell spheroids, wound healing and cell aggregation assays were utilized to assess cell-cell adhesion capacity. Immunofluorescence confocal microscopy and flow cytometry analysis were utilized to quantify expression of target signaling proteins, IHC analysis quantified the expression of target molecules in primary tumors and metastases. Pre-clinical models of orthotopic growth of colon cancer and metastatic diffusion to the liver were utilized. Xenotransplant transcriptome profiling analyzed transcription of EMT-related determinants. This led us to identify Trop-2 as a unique upregulated gene in colon cancer metastasis. Trop-2 was here shown to bind highly-expressed E-cadherin at the cell membrane. Trop-2 binding released E-cadherin from the cytoskeleton, inhibited cell-cell adhesion functions and activated signaling through β-catenin. This occurred in the absence of transcriptional downregulation of the CDH1 gene by EMT-associated transcription factors. The Trop-2/E-cadherin/β-catenin program was shown to lead to anti-apoptotic signaling, increased cell migration and enhanced cancer cell survival. In an orthotopic model of colon cancer, Trop-2 caused metastatic diffusion to the liver. The Trop-2-led E-cadherin-inactivation metastasis program was then found to induce metastatic relapse and shorter overall survival of colon cancer patients. Corresponding impact was indicated on breast, colon, ovary, uterus, stomach cancer metastatic diffusion, for broad impact on metastatic diffusion in human cancer. Acknowledgments:Support was provided by grants of Italian Ministry of Development (MI01_00424) and of University and Research (SCN_00558). M.T. was supported by the Programma Per Giovani Ricercatori “Rita Levi Montalcini” (Grant PGR12I7N1Z). Citation Format: Saverio Alberti, Emanuela Guerra, Valeria Relli, Rossano Lattanzio, Martina Ceci, Khouloud Boujnah, Valeria Garbo, Antonino Moschella, donato F. Altomare, Raffaella Depalo, Marco Trerotola. Trop-2 inactivates E-cadherin for metastatic diffusion in the absence of EMT [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2851.

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]

Hundreds of proteins/genes have been linked to the metastatic phenotype. However, consistent markers of tumour aggressiveness and metastatic potential in breast cancer patients were not identified, not even including proteomic analysis and large-scale genome sequencing.Metastasis-associated genes were predicted to include not only drivers of the metastatic phenotype, but also secondary events, together with adaptive, counterbalancing changes. Thus, to identify candidates with a required role in metastatic diffusion, we looked for genes that were concordantly dysregulated across orthogonal cancer metastasis settings. This led us to identify Trop-2 as uniquely upregulated and associated to metastasis in experimental models of breast cancer, as well as in other solid tumors. We identified functional inactivation of E-cadherin by Trop-2 as the main motor of metastatic diffusion of such metastatic systems. Trop-2 binding to E-cadherin inactivated its cell-cell adhesion function, through release from the cytoskeleton, for activation of β-catenin transcriptional activity. This led to anti-apoptotic signaling, increased cell migration capacity and enhanced cancer cell survival. We showed that this mechanism led to metastatic diffusion of xenotransplants growing in immunosuppressed mice. An E-cadherin-inactivation metastasis program was then shown to be recapitulated in breast cancer patients, as well as in other solid tumors, over 24 independent case series, encompassing 13,042 primary tumours. Aggressive triple-negative breast cancers were shown to be driven toward global relapse by Trop-2 overexpression, through E-cadherin inactivation and activation of β-catenin transcriptional activity. No disease recurrence was observed in control cases over +12 years of follow-up. These finding lead to a novel paradigm of a Trop-2-driven, E-cadherin-inactivation program as a main metastasis driver in solid tumors. This may open far-reaching perspectives in diagnostic procedures and anti-cancer therapies. Citation Format: Saverio Alberti, Marco Trerotola, Valeria Relli, Rossano Lattanzio, Martina Ceci, Khouloud Boujnah, Valeria Garbo, Antonino Moschella, Patrizia Querzoli, Massimo Pedriali, Laura Antolini, Emanuela Guerra. Trop-2 inactivation of E-cadherin drives triple negative breast cancer relapse [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD15-04.