The Genomic Signatures of Linitis Plastica Signal the Entrance into a New Era: Novel Approaches for Diagnosis and Treatment.

Linitis Plastica (LP) is a rare and aggressive tumor with a distinctive development pattern, leading to the infiltration of the gastric wall, the thickening of the gastric folds and a "leather bottle appearance". LP is an extremely heterogeneous tumor caused by mutations in oncogenic and tumor suppressive genes, as well as molecular pathways, along with mutations in stromal cells and proteins related to tight junctions. Elucidating the molecular background of tumorigenesis and clarifying the correlation between cancerous cells and stromal cells are crucial steps toward discovering novel diagnostic methods, biomarkers and therapeutic targets/agents. Surgery plays a pivotal role in LP management, serving both as a palliative and curative procedure. In this comprehensive review, we aim to present all recent data on the molecular background of LP and the novel approaches to its management.

Analysis of genomic and immune intratumor heterogeneity in linitis plastica via multiregional exome and T-cell receptor sequencing.

The molecular landscape and the intratumor heterogeneity (ITH) architecture of gastric linitis plastica (LP) are poorly understood. We performed whole-exome sequencing (WES) and T-cell receptor (TCR) sequencing on 40 tumor regions from four LP patients. The landscape and ITH at the genomic and immunological levels in LP tumors were compared with multiple cancers that have previously been reported. The lymphocyte infiltration was further assessed by immunohistochemistry (IHC) in LP tumors. In total, we identified 6339 non-silent mutations from multi-samples, with a median tumor mutation burden (TMB) of 3.30 mutations per Mb, comparable to gastric adenocarcinoma from the Cancer Genome Atlas (TCGA) cohort (P = 0.53). An extremely high level of genomic ITH was observed, with only 12.42%, 5.37%, 5.35%, and 30.67% of mutations detectable across 10 regions within the same tumors of each patient, respectively. TCR sequencing revealed that TCR clonality was substantially lower in LP than in multi-cancers. IHC using antibodies against CD4, CD8, and PD-L1 demonstrated scant T-cell infiltration in the four LP tumors. Furthermore, profound TCR ITH was observed in all LP tumors, with no T-cell clones shared across tumor regions in any of the patients, while over 94% of T-cell clones were restricted to individual tumor regions. The Morisita overlap index (MOI) ranged from 0.21 to 0.66 among multi-regions within the same tumors, significantly lower than that of lung cancer (P = 0.002). Our results show that LP harbored extremely high genomic and TCR ITH and suppressed T-cell infiltration, suggesting a potential contribution to the frequent recurrence and poor therapeutic response of this adenocarcinoma.

Comprehensive transcriptomic profiling and mutational landscape of primary gastric linitis plastica.

BACKGROUND: Primary gastric linitis plastica (GLP) is a distinct phenotype of gastric cancer with poor survival. Comprehensive molecular profiles and putative therapeutic targets of GLP remain undetermined. METHODS: We subjected 10 tumor-normal tissue pairs to whole exome sequencing (WES) and whole transcriptome sequencing (WTS). 10 tumor samples were all GLP which involves 100% of the gastric wall macroscopically. TCGA data were compared to generate the top mutated genes and the overexpressed genes in GLP. RESULTS: Our results reveal that GLP has distinctive genomic and transcriptomic features, dysfunction in the Hippo pathway is likely to be a key step during GLP development. 6 genes were identified as significantly highly mutated genes in GLP, including AOX1, ANKRD36C, CPXM1, PTPN14, RPAP1, and DCDC1). MUC6, as a previously identified gastric cancer driver gene, has a high mutation rate (20%) in GLP. 20% of patients in our GLP cohort had CDH1 mutations, while none had RHOA mutations. GLP exhibits high immunodeficiency and low AMPK pathway activity. Our WTS results showed that 3 PI3K-AKT pathway-related genes (PIK3R2, AKT3, and IGF1) were significantly up-regulated in GLP. Two genes were identified using immunohistochemistry (IHC), IGF2BP3 and MUC16, which specifically expressed in diffuse-type-related gastric cancer cell lines, and its knockdown inhibits PI3K-AKT pathway activity. CONCLUSIONS: We provide the first integrative genomic and transcriptomic profiles of GLP, which may facilitate its diagnosis, prognosis, and treatment.

Novel models for human scirrhous gastric carcinoma in vivo.

Human scirrhous gastric carcinoma, a diffusely infiltrating type of poorly differentiated gastric carcinoma also known as linitis plastica type carcinoma, is characterized by cancer cell infiltration and proliferation accompanied with extensive stromal fibrosis. We established two new gastric cancer cell lines, designated OUCM-8 and OCUM-11, which developed the characteristic biology of scirrhous gastric carcinoma upon orthotopic implantation in mice. Involvement of lymph nodes and liver metastasis was also found in both orthotopic models. Histologically, these orthotopic models showed proliferation with extensive fibrosis, resembling human scirrhous gastric cancer. Both cell lines were derived from ascites of patients with scirrhous gastric cancer. The growth of OCUM-8 and OCUM-11 cells following the addition of KGF, FGF, and EGF was increased significantly relative to untreated cells. An increase in the number of attached and spreading cells occurred following the addition of TGF-beta 1 in both cell lines. OCUM-11 cells showed microsatellite instability. Although subcutaneous scirrhous gastric cancer cells show medullary growth, most in vivo studies of scirrhous gastric cancer have used xenografted tumors implanted subcutaneously. Only in a few cases was it confirmed that these scirrhous gastric cancer cell lines retained the original histologic characteristics. Our orthotopic models should contribute to the elucidation of disease progression in situ and to the development of therapy for scirrhous gastric cancer.

A new mutation of E-cadherin gene in familial gastric linitis plastica cancer with extra-digestive dissemination.

Over a 12-month period, we diagnosed poorly differentiated infiltrative independent-cell gastric adenocarcinoma in two brothers and one sister aged 41 to 47 years. Their father had died from antral cancer at the age of 34 years. These cancers had two characteristic clinical features: rapid course and distant malignant dissemination. In all three patients, polymerase chain reaction-sequencing of the E-cadherin (CDH1) gene of white blood cells identified a heterozygous nonsense mutation of exon 3, producing a stop codon at position 95 (Q95X), resulting in a truncated protein. The alteration of this protein, which plays a crucial role in epithelial cell adhesion, probably explains the clinical expression in this type of familial diffuse gastric cancer.

Flow cytometry as a prognostic predictor in gastric linitis plastica.

UNLABELLED: Gastric linitis plastica (GLP) is a diffusely infiltrating carcinoma of the stomach that is usually diagnosed in an advanced stage and associated with poor prognosis. Recent studies to evaluate ploidy of these tumors are not conclusive. We undertook a retrospective study of 43 surgically treated patients with GLP (27 males, 16 females, mean age 65 years) to see if ploidy could be used to predict outcome. Flow cytometric DNA analysis was performed on paraffin-embedded tissue using the modified Hedley technique. Mean follow-up interval was 11 months (1-72 months) with 18 (42%) alive at end of study. The remaining 25 (58%) died with a mean survival of 7 months. Lymph node status was positive in 31 (70%) and negative in 12 (30%) of patients. Twenty-nine (67%) of tumors were diploid; 14 (33%) were aneuploid. Statistical analysis revealed overall survival correlated significantly (P = 0.04) only with lymph node status. Diploid tumors had 18 (60%) positive and 11 (40%) negative lymph nodes, whereas aneuploid tumors had 13 (93%) positive and 1 (7%) negative nodes. DNA content correlated significantly (P = 0.05) with lymph node status, but not with overall survival. Tumors with positive lymph nodes were 18 (51%) diploid and 13 (42%) aneuploid; tumors with negative nodes were 11 (92%) diploid and 1 (8%) aneuploid. CONCLUSIONS: The majority of GLP tumors manifest diploid characteristics, and the presence or absence of lymph node metastasis is a major determinant in overall survival.