Sensitivity of gastric cancer cells to all-trans retinoic acid, a new agent in the personalized treatment of this heterogeneous tumor: definition of a predictive gene-expression model that may be used for the selection of patients who may benefit from retinoid-based treatments (Xenografts). Sensitivity of gastric cancer cells to all-trans retinoic acid, a new agent in the personalized treatment of this heterogeneous tumor: definition of a predictive gene-expression model that may be used for the selection of patients who may benefit from retinoid-based treatments (Xenografts)

All-trans retinoic acid (ATRA) is used in the treatment of Acute Promyelocytic Leukemia (APL) with exceptional results, inducing long-lasting remissions in 78% of the patients. In previous studies (Bolis M et al., Ann Oncol. 2017, 28:611; Centritto F et al., EMBO Mol Med. 2015, 7:950) we demonstrated the therapeutic potential of ATRA in the personalized treatment of breast cancer. The present study is aimed at providing pre-clinical evidence supporting the use of pharmacological strategies based on ATRA in the management of stomach cancer, a very heterogeneous type of tumor, which lacks effective therapeutic options other than surgery. To define the sensitivity of gastric cancer to the anti-proliferative action of ATRA, we used 27 cell-lines, recapitulating the heterogeneity of the tumor. Fourteen of these cell-lines are characterized by a G-DIF phenotype, while the remainders present with a G-INT phenotype. Each cell-line was exposed to increasing concentrations of ATRA and the growth-inhibitory effects of the retinoid were evaluated at 3, 6, and 9 days. The 27 cell-lines were ranked for their sensitivity to the retinoid with the “ATRA-score”, a continuous/quantitative index, which we developed. The results indicate that the cell-lines can be divided into 3 separate groups characterized by high, intermediate and low sensitivity to ATRA. No significant correlation between ATRA-sensitivity and the G-DIF or G-INT phenotype is observed in our panel of cell-lines. To support the results obtained with the cell-lines, we evaluated the anti-proliferative effects exerted by ATRA on short-term tissue slice cultures of primary tumors derived from 13 cases of stomach cancer, which we classified as G-DIF or G-INT following determination of the basal gene-expression profiles with the use of RNA-sequencing studies. The results obtained with the short-term tissue culture model confirm the data generated with the cell-lines. The whole genome RNA-sequencing studies performed in the cell-lines and short-term tissue cultures in basal conditions allowed us to define a model consisting of 42 genes whose expression is quantitatively correlated with ATRA-sensitivity. The model was used to predict the sensitivity of gastric cancer cases to ATRA using the TCGA dataset. The results obtained indicate that approximately 60% of the gastric cancer cases are predicted to be characterized by high/intermediate sensitivity to ATRA, regardless of the G-DIF or G-INT phenotype. In conclusion, our results support the concept that ATRA-based therapeutic strategies are likely to be beneficial in the majority of stomach cancer cases. In addition, we generate a gene-expression tool that may be used for the selection of ATRA-sensitive patients in the clinics.

全反式维甲酸（All-trans retinoic acid, ATRA）在急性早幼粒细胞白血病（Acute Promyelocytic Leukemia, APL）的治疗中疗效卓越，可使78%的患者获得长期缓解。既往研究（Bolis M等，《Ann Oncol》，2017，28:611；Centritto F等，《EMBO Mol Med》，2015，7:950）已证实ATRA在乳腺癌个体化治疗中的治疗潜力。本研究旨在为基于ATRA的药理学策略用于胃癌管理提供临床前证据——胃癌是一类高度异质性的肿瘤，除手术外缺乏有效的治疗选择。为明确胃癌细胞对ATRA抗增殖作用的敏感性，我们采用27株能够重现该肿瘤异质性的细胞系开展实验。其中14株细胞系具有G-DIF表型，剩余细胞系则呈现G-INT表型。将每株细胞系置于递增浓度的ATRA环境中培养，并分别于第3、6、9天评估该维甲酸类化合物的生长抑制效果。我们开发了一种连续定量指标“ATRA评分（ATRA-score）”，用于对27株细胞系的维甲酸敏感性进行排序。结果显示，细胞系可被划分为高、中、低ATRA敏感性三个独立组别。在本研究的细胞系面板中，未观察到ATRA敏感性与G-DIF或G-INT表型存在显著相关性。为验证细胞系实验结果，我们对13例胃癌患者来源的原发性肿瘤短期组织切片培养模型进行了ATRA抗增殖效应评估；通过RNA测序（RNA-sequencing）分析基础基因表达谱，我们将这13例肿瘤分为G-DIF或G-INT表型。短期组织培养模型得到的结果与细胞系实验数据一致。通过对细胞系和短期组织培养模型在基础状态下进行全基因组RNA测序，我们构建了一个包含42个基因的模型，其表达水平与ATRA敏感性呈定量相关。利用该模型，我们借助TCGA数据集预测胃癌患者对ATRA的敏感性。结果表明，约60%的胃癌患者被预测为具有高/中度ATRA敏感性，且这一结果与G-DIF或G-INT表型无关。综上，本研究结果支持基于ATRA的治疗策略有望使大多数胃癌患者获益这一观点。此外，我们还构建了一款基因表达工具，可用于临床中筛选对ATRA敏感的胃癌患者。