Personalized therapeutic strategies in HER2-driven gastric cancer.

BACKGROUND: Trastuzumab is the only approved targeted therapy in patients with HER2-amplified metastatic gastric cancer (GC). Regrettably, in clinical practice, only a fraction of them achieves long-term benefit from trastuzumab-based upfront strategy. To advance precision oncology, we investigated the therapeutic efficacy of different HER2-targeted strategies, in HER2 "hyper"-amplified (≥ 8 copies) tumors. METHODS: We undertook a prospective evaluation of HER2 targeting with monoclonal antibodies, tyrosine kinase inhibitors and antibody-drug conjugates, in a selected subgroup of HER2 "hyper"-amplified gastric patient-derived xenografts (PDXs), through the design of ad hoc preclinical trials. RESULTS: Despite the high level of HER2 amplification, trastuzumab elicited a partial response only in 2 out of 8 PDX models. The dual-HER2 blockade with trastuzumab plus either pertuzumab or lapatinib led to complete and durable responses in 5 (62.5%) out of 8 models, including one tumor bearing a concomitant HER2 mutation. In a resistant PDX harboring KRAS amplification, the novel antibody-drug conjugate trastuzumab deruxtecan (but not trastuzumab emtansine) overcame KRAS-mediated resistance. We also identified a HGF-mediated non-cell-autonomous mechanism of secondary resistance to anti-HER2 drugs, responsive to MET co-targeting. CONCLUSION: These preclinical randomized trials clearly indicate that in HER2-driven gastric tumors, a boosted HER2 therapeutic blockade is required for optimal efficacy, leading to complete and durable responses in most of the cases. Our results suggest that a selected subpopulation of HER2-"hyper"-amplified GC patients could strongly benefit from this strategy. Despite the negative results of clinical trials, the dual blockade should be reconsidered for patients with clearly HER2-addicted cancers.

Optimized EGFR Blockade Strategies in EGFR Addicted Gastroesophageal Adenocarcinomas.

PURPOSE: Gastric and gastroesophageal adenocarcinomas represent the third leading cause of cancer mortality worldwide. Despite significant therapeutic improvement, the outcome of patients with advanced gastroesophageal adenocarcinoma is poor. Randomized clinical trials failed to show a significant survival benefit in molecularly unselected patients with advanced gastroesophageal adenocarcinoma treated with anti-EGFR agents. EXPERIMENTAL DESIGN: We performed analyses on four cohorts: IRCC (570 patients), Foundation Medicine, Inc. (9,397 patients), COG (214 patients), and the Fondazione IRCCS Istituto Nazionale dei Tumori (206 patients). Preclinical trials were conducted in patient-derived xenografts (PDX). RESULTS: The analysis of different gastroesophageal adenocarcinoma patient cohorts suggests that EGFR amplification drives aggressive behavior and poor prognosis. We also observed that EGFR inhibitors are active in patients with EGFR copy-number gain and that coamplification of other receptor tyrosine kinases or KRAS is associated with worse response. Preclinical trials performed on EGFR-amplified gastroesophageal adenocarcinoma PDX models revealed that the combination of an EGFR mAb and an EGFR tyrosine kinase inhibitor (TKI) was more effective than each monotherapy and resulted in a deeper and durable response. In a highly EGFR-amplified nonresponding PDX, where resistance to EGFR drugs was due to inactivation of the TSC2 tumor suppressor, cotreatment with the mTOR inhibitor everolimus restored sensitivity to EGFR inhibition. CONCLUSIONS: This study underscores EGFR as a potential therapeutic target in gastric cancer and identifies the combination of an EGFR TKI and a mAb as an effective therapeutic approach. Finally, it recognizes mTOR pathway activation as a novel mechanism of primary resistance that can be overcome by the combination of EGFR and mTOR inhibitors.See related commentary by Openshaw et al., p. 2964.

In vitro generation of primary cultures of human hyalocytes.

Purpose: A growing number of studies on animal models have demonstrated that some ocular diseases are the result of the interaction between hyalocytes and the ocular inflammatory setting. Endogenous and exogenous substances might alter the structure and behavior of hyalocytes that can contribute to the pathogenesis of some ocular diseases. Obtaining primary cultures of human hyalocytes could help understand the role of these cells in response to different treatments. Methods: Hyalocytes were isolated from eyes of 54 patient volunteers subjected to vitrectomy for different clinical reasons. By testing different matrices and growth media, we reproducibly generated primary cultures of hyalocytes that we characterized morphologically and biologically, basally and upon treatment with several agents (basic fibroblast growth factor (bFGF), transforming growth factor beta 1 (TGF-ß), platelet-derived growth factor subunit-BB (PDGF-BB), ascorbic acid, dexamethasone, and hydrogen peroxide). Results: We were able to generate primary cultures from vitreous human samples, growing the cells on collagen-coated plates in Iscove's modified Dulbecco's medium supplemented with 10% fetal bovine serum; primary cells expressed the hyalocyte markers. Specific cytoskeletal modifications were observed upon treatment with bFGF, TGF-ß, PDGF-BB, ascorbic acid, dexamethasone, and hydrogen peroxide. Only bFGF was able to promote cell growth and hyaluronic acid production. Conclusions: We describe for the first time the generation and the characterization of primary cultures of human hyalocytes from living donors. Although human hyalocytes share some characteristics with animal hyalocytes, human hyalocytes have their own features typical of the species, confirming how important human experimental models are for investigating human pathologies and their treatments.

A Comprehensive PDX Gastric Cancer Collection Captures Cancer Cell-Intrinsic Transcriptional MSI Traits.

Gastric cancer is the world's third leading cause of cancer mortality. In spite of significant therapeutic improvements, the clinical outcome for patients with advanced gastric cancer is poor; thus, the identification and validation of novel targets is extremely important from a clinical point of view. We generated a wide, multilevel platform of gastric cancer models, comprising 100 patient-derived xenografts (PDX), primary cell lines, and organoids. Samples were classified according to their histology, microsatellite stability, Epstein-Barr virus status, and molecular profile. This PDX platform is the widest in an academic institution, and it includes all the gastric cancer histologic and molecular types identified by The Cancer Genome Atlas. PDX histopathologic features were consistent with those of patients' primary tumors and were maintained throughout passages in mice. Factors modulating grafting rate were histology, TNM stage, copy number gain of tyrosine kinases/KRAS genes, and microsatellite stability status. PDX and PDX-derived cells/organoids demonstrated potential usefulness to study targeted therapy response. Finally, PDX transcriptomic analysis identified a cancer cell-intrinsic microsatellite instability (MSI) signature, which was efficiently exported to gastric cancer, allowing the identification, among microsatellite stable (MSS) patients, of a subset of MSI-like tumors with common molecular aspects and significant better prognosis. In conclusion, we generated a wide gastric cancer PDX platform, whose exploitation will help identify and validate novel "druggable" targets and optimize therapeutic strategies. Moreover, transcriptomic analysis of gastric cancer PDXs allowed the identification of a cancer cell-intrinsic MSI signature, recognizing a subset of MSS patients with MSI transcriptional traits, endowed with better prognosis. SIGNIFICANCE: This study reports a multilevel platform of gastric cancer PDXs and identifies a MSI gastric signature that could contribute to the advancement of precision medicine in gastric cancer.