HLA-DR antigen expression in intestinal-type and diffuse-type gastric carcinoma

The dawn of precision medicine in diffuse-type gastric cancer

Gastric cancer (GC) is one of the most common malignancies worldwide. The histology- and morphology-based Lauren classification of GC has been widely used for over 50 years in clinical practice. The Lauren classification divides GC into intestinal and diffuse types, which have distinct etiology, molecular profiles, and clinicopathological features. Diffuse-type GC (DGC) accounts for approximately 30% of GCs. Tumor cells lack adhesion and infiltrate the stroma as single cells or small subgroups, leading to easy dissemination in the abdominal cavity. Clinically, DGC has aggressive traits with a high risk of recurrence and metastasis, which results in unfavorable prognosis. Although systemic chemotherapy is the main therapeutic approach for recurrent or metastatic GC patients, clinical benefits are limited for patients with DGC. Therefore, it is urgent to develop effective therapeutic strategies for DGC patients. Considerable research studies have characterized the molecular and genomic landscape of DGC, of which tight junction protein claudin-18 isoform 2 (CLDN18.2) and fibroblast growing factors receptor-2 isoform IIIb (FGFR2-IIIb) are the most attractive targets because of their close association with DGC. Recently, the impressive results of two phase II FAST and FIGHT trials demonstrate proof-of-concept, suggesting that anti-CLDN18.2 antibody (zolbetuximab) and FGFR2-IIIb antibody (bemarituzumab) are promising approaches for patients with CLDN18.2-positive and FGFR2-IIIb-positive GC, respectively. In this review, we summarize the clinicopathological features and molecular profiles of DGC and highlight a potential therapeutic target based on the findings of pivotal clinical trials.

Recent advances in immune therapies for gastric cancer

Gastric cancer (GC) is an aggressive malignancy that is the third leading cause of cancer mortality worldwide. Localized GC can be cured with surgery, but most patients present with more advanced non-operable disease. Until recently, treatment options for relapsed and refractory advanced GC have been limited to combination chemotherapy regimens, HER-2 directed therapy, and radiation, which lead to few durable responses. Over the past decade, there have been significant advances in our understanding of the molecular and immune pathogenesis of GC. The infectious agents Epstein-Barr virus and Helicobacter pylori perturb the gastric mucosa immune equilibrium, which creates a microenvironment that favors GC tumorigenesis and evasion of immune surveillance. Insights into immune mechanisms of GC have translated into novel therapeutics, including immune checkpoint inhibitors, which have become a treatment option for select patients with GC. Furthermore, chimeric antigen receptor T-cell therapies have emerged as a breakthrough treatment for many cancers, with recent studies showing this to be a potential therapy for GC. In this review, we summarize the current state of knowledge on immune mechanisms of GC and the status of emerging immunotherapies to treat this aggressive cancer, as well as outline current challenges and directions for future research.

Infiltrating and peripheral immune cell analysis in advanced gastric cancer according to the Lauren classification and its prognostic significance

BACKGROUND

The correlation between immune cells and the Lauren classification subtypes and their prognostic impact in advanced gastric cancer (AGC) are unknown.

METHODS

Circulating natural killer (NK) cells, CD4⁺ and CD8⁺ T cells, regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) were quantified in peripheral blood mononuclear cells (PBMCs) from 67 patients with untreated AGC enrolled in the PRODIGE 17-ACCORD 20 trial. CD56⁺ cells (NK), CD8⁺, and FoxP3⁺ (Treg) tumor-infiltrating lymphocytes (TILs) were assessed in tumor samples.

RESULTS

Circulating NK and Treg proportions were significantly lower in patients with diffuse/mixed-type AGC (n = 27) than those with intestinal type (n = 40; median 6.3% vs 11.5%; p = 0.02 and median 3.3% vs 5.2%; p = 0.03, respectively). Proportions of circulating MDSC, CD4⁺ and CD8⁺ T cells were not associated with one pathological type. Among tumor-infiltrating cells, CD8⁺ T cells, but not NK or FoxP3⁺ cells, were significantly lower in diffuse/mixed-type AGC (median 21 vs 59 cells/field; p = 0.009). Patients with high circulating NK cell counts (> 17%) had a better overall survival than those with < 17% (HR 0.40; 95% CI [0.15-1.06]; p = 0.04). Patients with high CD8⁺ TIL counts (> 31 cells/field) had significantly longer overall survival (HR 0.44; 95% CI [0.21-0.92]; p = 0.02). The prognostic value of CD8⁺ TILs was maintained after adjustment for confounding factors, including the Lauren classification (HR = 0.42; 95% CI [0.18-0.96]; p = 0.039).

CONCLUSION

Diffuse/mixed-type AGC has lower rates of CD8⁺ TILs and circulating NK cells and Tregs than the intestinal type. This "cold tumor" phenotype may be associated with a worse outcome.

PGP9.5 methylation in diffuse-type gastric cancer

Diffuse-type gastric cancer (DGC) is the most deadly form of gastric cancer and is frequently accompanied by peritoneal dissemination and metastasis. The specific molecular events involved in DGC pathogenesis remain elusive. Accumulating evidence of epigenetic inactivation in tumor suppressor genes led us to conduct a comprehensive screen to identify novel methylated genes in human cancers using pharmacologic unmasking and subsequent microarray analysis. We compared differential RNA expression profiles of DGC and intestinal-type gastric cancer (IGC) cell lines treated with 5-aza-2'-deoxycytidine using microarrays containing 22,284 genes. We identified 16 methylated genes, including many novel genes, in DGC cell lines and studied PGP9.5 with particular interest. In primary gastric cancers, PGP9.5 was found to be more frequently methylated in DGCs (78%) than in IGCs (36%; DGC versus IGC, P < 0.05). Furthermore, real-time methylation-specific PCR analysis of PGP9.5 showed relatively higher methylation levels in DGC than in IGC. Our data thus implicate a molecular event common in the DGC phenotype compared with IGC.

Relationship between the downregulation of HLA class I antigen and clinicopathological significance in gastric cancer

AIM: To discuss the expression of human leukocyte antigen (HLA) class I antigens in gastric cancer and correlate these with pathologic type and TNM stage.

METHODS: The expression of HLA class I antigen was detected by immunohistochemistry in 185 specimens of gastric cancer, 20 gastric cancer specimens with lymphatic metastasis and 22 controls of normal gastric mucosa using four monoclonal antibodies.

RESULTS: The expression of HLA class I antigen (B/C locus) was significantly downregulated in gastric cancer and in lymphatic metastasis than that in normal gastric mucosa (χ² = 7.712, P<0.05). The expression of other HLA class I antigens was also downregulated, but the change was slight. There was no relationship between the downregulation of HLA class I antigen and that of β2m and LMP2. The expression of HLA class I (B/C locus) was statistically correlated with pathologic stage in gastric adenocarcinoma (χ² = 4.164, P<0.05).

CONCLUSION: The expression of HLA class I antigen (B/C locus) was obviously downregulated in gastric cancer and in lymphatic metastasis. This abnormal expression would provide the tumor cells with a way to avoid immunological recognition.

HLA-DR Antigen and Bax Protein Expression in Patients with Primary Non-Hodgkin's Gastric Lymphoma

Primary gastric lymphoma represents a rare gastrointestinal malignancy with an unclear prognosis. The aim of this study was to determine the prognostic significance of HLA-DR antigen and bax expression in patients with primary non-Hodgkin's gastric lymphoma. We immunohistochemically studied bax protein and HLA-DR antigen expression in 36 B-cell, MALT-type primary gastric lymphoma patients diagnosed and treated in our department from 1990 to 1995. Ten non-malignant gastric tissue specimens were used as benign controls. Clinicopathological and survival data were correlated with the staining results. HLA-DR antigen expression was observed in 33 gastric lymphoma patients (91.7%). Positive bax staining was found in 24 gastric lymphomas (66.7%) and in none of the benign cases studied. In the univariate analysis, those gastric lymphoma patients who expressed HLA-DR antigen in more than 15% of their tumor cells, presented a significantly improved 5-year survival rate (75% vs. 37.5%, p = 0.04). Furthermore, gastric lymphoma patients who were bax(+)/HLA-DR(+) had a statistically better overall survival compared to those who were bax(-)/HLA-DR(-) (82.4% vs. 25%, p = 0.01). HLA-DR antigen expression was associated with a favorable clinical outcome. Its expression improved the predictive value of bax protein expression in non-Hodgkin's gastric lymphoma patients. The combined use of these markers permits the identification of a high-risk group of patients that may benefit from a more aggressive therapeutic approach.

Relationship between the expression of HLA-DR antigen and the effectiveness of preoperative hyperthermo-chemo-radiotherapy in oesophageal cancer

Based on the hypothesis that tumour cells expressing HLA-DR antigen would easily be damaged by the local immune response during preoperative treatments, the relationship was investigated between the expression of HLA-DR antigen in the oesophageal cancer and the effectiveness of the preoperative treatment. Immunohistochemical staining for the detection of HLA-DR antigen in cancer cells from biopsy specimens obtained before undergoing preoperative hyperthermo-chemo-radiotherapy (HCR therapy) in patients with oesophageal squamous cell carcinoma was performed, and the relationship between the expression of HLA-DR antigen and the effectiveness of HCR therapy was evaluated according to a histopathologic examination of resected specimen. A total of 35 cases were examined in which 14 showed strongly positive staining (+2), 14 weakly positive staining (+) and seven negative staining (-). No significant differences in the clinicopathologic factors between the groups were observed. In the 14 strongly positive HLA-DR antigen cases, nine were markedly effective (grade 3) (64.3%), four were moderately effective (grade 2) (28.6%) and one was slightly effective or ineffective (grade 1, 0) (7.1%). In the 14 weakly positive HLA-DR antigen cases, the markedly, moderately and slightly or ineffective cases numbered four (28.6%), eight (57.1%) and two (14.3%), respectively. On the other hand, in the seven patients showing no HLA-DR expression, the markedly, moderately and slightly effective cases numbered one (14.3%), two (28.6%) and four (57.1%), respectively. A statistical difference was observed between the cases of strongly positive and negative staining for HLA-DR antigen (p < 0.05). The expression of HLA-DR antigen in oesophageal cancer cells is thus considered to potentially be a valuable factor for predicting the effectiveness of preoperative treatment.

Immunohistochemically demonstrated expression of HLA-DR antigen in colorectal adenocarcinomas and its relation to clinicopathological features

We studied 148 colorectal adenocarcinomas to clarify any correlation between HLA-DR antigen expression on tumor cells and histopathological features. Paraffin sections of formalin-fixed tissues were stained with HLA-DR antigen using the indirect immunoperoxidase technique. All the tumor tissues were divided into two groups, depending on the incidence of HLA-DR-positive cells (greater and lesser than 50%). Carcinoma tissues with a higher incidence showed less mural invasion, lymphoductal invasion, venous invasion, lymphonodular metastasis, and peritoneal metastasis. Tissues with a high HLA-DR reactivity were more often observed for Dukes' A and B stages, whereas those with a low HLA-DR positivity were frequently Dukes' C and D stages. As for the cumulative survival rate, the group with high HLA-DR expression demonstrated significantly better survival. We speculate that HLA-DR expression by colorectal cancer cells exerts a favorable influence on clinical course.

An immunohistochemical study of p53 protein in the different histological subtypes of gastric carcinoma

p53 mutations are known to occur frequently in human cancers, including gastric carcinomas. Previous studies of its incidence in gastric carcinomas had shown a varying incidence ranging from a low of 4% to as high as 57%. In this study, 42 cases of gastric carcinomas were analyzed for p53 using a commercially available mouse monoclonal antibody in routinely formalin-fixed paraffin-embedded tissue sections. These included 22 intestinal-type (7 well/moderately differentiated and 15 poorly differentiated), 16 diffuse-type and 4 mixed. Altogether, 60% of our cases stained positively for p53. Overall, well/moderately differentiated intestinal-type carcinomas stained more frequently for p53 than poorly differentiated intestinal-type carcinomas (p < 0.075). A comparison between the incidence in diffuse-type (69%) and intestinal type (55%) was unremarkable. p53 staining was also present in 3 of the 4 early cases studied. The results suggest that p53 mutations play an important role in carcinogenesis in gastric carcinoma and further implies that p53 mutation may be an early occurrence during tumor transformation.

Local immune response to tumor invasion in esophageal squamous cell carcinoma. The expression of human leukocyte antigen-DR and lymphocyte infiltration

BACKGROUND

The purpose of this study was to investigate the local immune response to tumor invasion in esophageal squamous cell carcinoma by using an immunohistochemical examination of the expression of human leukocyte antigen- (HLA) DR and lymphocyte infiltration.

METHODS

The paraffin embedded sections from 108 patients with esophageal squamous cell carcinoma were studied immunohistochemically, using the streptavidin biotin peroxidase method with monoclonal antibody (HLA-DR, T-cell, and B-cell) in the 68 noninvasive sites of cancer (intraepithelial carcinoma) and the 108 invasive sites of cancer.

RESULTS

The expression of HLA-DR antigen was detected in 49 of 108 cases (45%) of esophageal cancer. The expression of this antigen was more predominant in intraepithelial carcinoma than at the invasive sites of cancer (60% versus 22%, P < 0.01). Among the 40 cases with positive staining for HLA-DR antigen in intraepithelial carcinoma, negative staining of the invasion portion was shown in 27 (67.5%) cases. On the other hand, in the 28 cases with negative staining in intraepithelial carcinoma, 27 cases (96.4%) were also negative at the invasive sites. T-cell infiltration was significantly recognized at the area of HLA-DR antigen expression at the sites of both intraepithelial carcinoma and tumor invasion. However, no significant relationship was observed between the HLA-DR antigen expression and long term survival at this time.

CONCLUSIONS

These results suggest that the local immune response to the HLA-DR may prevent tumor invasion, whereas the negative expression of HLA-DR antigen is a significant factor facilitating tumor invasion in esophageal squamous cell carcinoma.

The MHC class-II and CD44 molecules are involved in the induction of tumour necrosis factor (TNF) gene expression by human monocytes stimulated with tumour cells

Tumour necrosis factor alpha (TNF) mRNA is detected in the macrophage infiltrate surrounding the tumour, but the cellular/molecular interactions leading to TNF gene expression in macrophages are unknown. The in vitro system in which human blood monocytes are stimulated with human cancer cells for TNF release was used to study such interactions. Monoclonal antibodies (MAbs) against various adhesion molecules (LFA-1, LFA-3, ICAM-1, VNR, VLA beta I chain) were unable to block TNF production in co-culture of monocytes with a human pancreatic carcinoma (HPC) cell line. However, anti-CD44 and anti-HLA-DR MAbs effectively blocked TNF release and TNF-mRNA induction in monocytes. Pre-incubation of monocytes with anti-HLA-DR and tumour cells with anti-CD44 MAbs had a similar effect. It was concluded that CD44 molecules are involved in tumour-monocyte interactions and that HLA-DR determinants of monocytes are engaged in signal transduction for TNF gene activation. These findings may suggest that certain surface determinants of tumour cells act as ligands for MHC class-II molecules and induce TNF production in monocytes.

Expression of HLA-class II antigen in gastric carcinomas. Its relationship to histopathological grade, lymphocyte infiltration and five-year survival rate

To investigate whether the expression of HLA-DR antigen in gastric carcinomas is associated with the survival rate, we studied 70 cases of gastric carcinoma using a monoclonal antibody. Forty-seven cases (67%) stained positively, including 31 differentiated carcinomas, and 16 undifferentiated carcinomas. A close correlation was found between expression of HLA-DR antigen and differentiation of the tumor cells. Marked lymphocyte infiltration was seen in the HLA-DR antigen positive cancers. In advanced gastric cancers, the 5-year survival rate of patients with HLA-DR antigen positive cancers was significantly higher (67.5%) than that of patients with HLA-DR antigen negative cancers (40%). The data suggest that the expression of HLA-DR antigen in gastric carcinomas may reflect the degree of tumor cell differentiation, and influence the host immune response and prognosis.

An immunohistochemical study of ras oncoprotein expression in gastric carcinoma

BACKGROUND

Previous studies have shown that ras oncoprotein is overexpressed in gastric carcinoma. It is unsettled whether there is differential expression of this oncoprotein in the two major subtypes of gastric carcinoma--intestinal type and diffuse type.

METHODS

Forty-four cases of gastric carcinomas (24 intestinal type, 18 diffuse type, and 2 mixed according to the Lauren classification) were analyzed for ras oncoprotein expression using commercially available antibodies in routinely formaldehyde-fixed, paraffin-embedded tissue sections.

RESULTS

Altogether, 13 cases stained unequivocally, and these appeared as granular cytoplasmic staining in tumor cells. Only five were intestinal-type carcinomas; the remaining eight were diffuse type and included two intramucosal carcinomas. When the comparison between the two subtypes was limited only to the poorly differentiated carcinomas, the difference was statistically significant (P < 0.05). ras Oncoprotein also was strongly expressed in normal duodenal mucosa as well as areas of gastric intestinal metaplasia.

CONCLUSIONS

These results suggest that the strong expression of ras oncoprotein in gastric intestinal metaplasia may be merely a reflection of metaplastic change to an intestinal epithelial phenotype. The differential expression of ras oncoprotein between diffuse-type and poorly differentiated intestinal-type gastric carcinoma implies that these are two distinct subtypes of gastric carcinoma.