Immunohistochemical analysis of the poorly differentiated stomach adenocarcinoma with medullary growth pattern

Poorly differentiated gastric adenocarcinoma with medullary features (poor medullary) is distinguished by a propensity for hepatic metastasis. To classify it antigenically, we compared it to poorly differentiated adenocarcinoma with scirrhous growth pattern (poor scirrhous), well and moderately differentiated adenocarcinoma (differentiated adenocarcinoma), and normal gastric mucosa (foveolar and deep epithelium) using immunohistochemistry with antibodies against CEA, AFP, NSE, and Lewis-type antigens. Lewis^b antigen was significantly associated with differentiated adenocarcinoma and foveolar epithelium, although Lewis^x antigen was significantly expressed in poor medullary, poor scirrhous, and deep gland epithelium. From the viewpoint of expression of Lewis^a, there was no significant differentiation between poor medullary and differentiated adenocarcinoma, but it was definite between poor scirrhous and differentiated adenocarcinoma. Therefore, we conclude that in antigenic expression, poor medullary carcinoma is allied with differentiated adenocarcinoma rather than poorly differentiated scirrhous carcinoma. © 1996 Wiley-Liss, Inc.     

Remodeling the cancer epigenome: mutations in the SWI/SNF complex offer new therapeutic opportunities

Introduction: Cancer genome sequencing studies have discovered mutations in members of the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin-remodeling complex in nearly 25% of human cancers. The SWI/SNF complex, first discovered in S. cerevisiae, shows strong conservation from yeast to Drosophila to mammals, contains approximately 10–12 subunits and regulates nucleosome positioning through the energy generated by its ATPase subunits. The unexpected finding of frequent mutations in the complex has fueled studies to identify the mechanisms that drive tumor development and the accompanying therapeutic vulnerabilities.

Areas covered: In the review, we focus upon the potential roles different SWI/SNF subunit mutations play in human oncogenesis, their common and unique mechanisms of transformation and the potential for translating these mechanisms into targeted therapies for SWI/SNF-mutant tumors.

Expert opinion: We currently have limited insights into how mutations in different SWI/SNF subunits drive the development of human tumors. Because the SWI/SNF complex participates in a broad range of normal cellular functions, defining specific oncogenic pathways has proved difficult. In addition, therapeutic options for SWI/SNF-mutant cancers have mainly evolved from high-throughput screens of cell lines with mutations in different subunits. Future studies should follow a more coherent plan to pinpoint common vulnerabilities among these tumors.     

SWI/SNF染色质重塑复合体及其与肿瘤病理生理相关性的研究进展

SWI/SNF复合体是具有ATP酶活性的染色质结构重塑复合体,通过调控核小体空间位置、结构的方式产生相应表观遗传学效应。SWI/SNF复合体表观遗传学效应主要涉及细胞增殖、分化及DNA修复等过程,其有序进行密切相关复合体的完整性。体细胞内,累及SWI/SNF复合体编码基因的失能性突变可造成其亚基缺失,并破坏相关细胞生理活动的有序进行。最终,导致多种肿瘤的发生与进展。全基因组测序示,SWI/SNF复合体编码基因失能性突变比例在泛癌组织中达25%,略低于经典抑癌基因TP53编码基因突变率(26%)。SWI/SNF复合体内亚基缺失所产生的促癌效应具有多层次性。在表观遗传学层面,亚基缺失可阻遏SWI/SNF复合体有效拮抗多种癌症相关表观遗传学效应因子,如PRC合体的转录效应。导致细胞去分化或过度增殖。在基因组层面,由于SWI/SNF复合体参与以同源重组修复为主的DNA修复进程,可导致基因组不稳定及癌症相关突变的累积。此外,亚基缺失可转变SWI/SNF复合体功能表观遗传学功能,致使其以“残余”效应促进肿瘤进展。由于SWI/SNF复合体部分亚基在细胞生理功能上存在互补性且密切参与DNA双链修复途径,靶向其特定亚基或使用PARP抑制剂,可产生合成致死效应而有效抑制SWI/SNF复合体缺陷肿瘤进展。部分SWI/SNF复合体缺陷肿瘤,如ARID1A缺陷型,其肿瘤免疫微环境存在显著抑制状态,使其对肿瘤免疫治疗存在良好的敏感性。     

肿瘤中SWI/SNF复合物亚基变异的作用及其相关治疗策略进展

SWI/SNF复合物是调节真核细胞基因表达的一种重要而复杂的多亚基蛋白复合物，广泛参与信号转导、细胞周期及分化等各种生物过程，其亚基基因在20%以上的恶性肿瘤中发生突变。本文综述了该复合物及其亚基在恶性肿瘤中的作用和特征，并探讨SWI/SNF复合物在肿瘤治疗中的潜在临床应用。     

DNA错配修复蛋白表达与胃腺癌临床病理特征的关系及意义

目的:检测DNA错配修复（mismatch repair,MMR）主要蛋白（MLH1、MSH2、MSH6和PMS2)在人胃腺癌组织中的表达,并分析错配修复缺陷（defective mismatch repair,dMMR）与胃腺癌临床病理因素及预后的关系。方法:采用免疫组织化学染色法检测4种MMR蛋白（MLH1、MSH2、MSH6和PMS2)在120例人胃腺癌组织中的表达,并从癌症基因组图谱（The Cancer Genome Atlas,TCGA）公共数据库下载432例胃腺癌患者的临床病理资料和微卫星不稳定性（microsatellite instability,MSI）的检测结果,分析MSI与胃腺癌临床病理特征的关系,利用TCGA的数据分析高频度微卫星不稳定（MSI-H）与胃腺癌患者预后的关系。结果:免疫组化染色结果显示在120例胃腺癌组织中,MMR蛋白表达正常（pMMR）组106例（88.3%）,MMR蛋白表达缺失（dMMR)组14例（11.7%）,其中MLH1缺失2例（1.7%）、PMS2缺失13例（10.8%）、MLH1和PMS2共同缺失2例（1.7%）、MSH2和MSH6共同缺失1例（0.8%）。统计分析结果显示,dMMR与胃腺癌淋巴结转移相关（P=0.022）,而与其他临床病理因素无关。TCGA数据统计分析结果显示,MSI-H与胃腺癌患者年龄（P=0.001)、性别（P=0.000)、原发肿瘤部位（P=0.000)、Lauren分型（P=0.011）、肿瘤浸润深度T分期（P=0.024)、淋巴结有无转移（P=0.008)有关。Kaplan-Meier生存分析结果显示MSI-H型胃腺癌患者有预后更好的趋势,但差异不具有统计学意义（P=0.070）。结论:120例中国胃腺癌患者中MSI/dMMR型胃腺癌占比为11.7%,且dMMR状态与胃腺癌的淋巴结转移呈负相关;MSI-H型胃腺癌患者具有年龄大、多为女性、肿瘤多位于胃远端、肿瘤浸润深度T分期低、无淋巴结转移的特征,且MSI-H型胃腺癌具有预后更好的趋势,但不具有统计学意义。MSI状态与胃癌预后的关系尚需进一步深入研究和大样本数据的验证。     

The silencing of the SWI/SNF subunit and anticancer gene BRM in Rhabdoid tumors

Rhabdoid sarcomas are highly malignant tumors that usually occur in young children. A key to the genesis of this tumor is the mutational loss of the BAF47 gene as well as the widespread epigenetic suppression of other key anticancer genes. The BRM gene is one such epigenetically silenced gene in Rhabdoid tumors. This gene codes for an ATPase catalytic subunit that shifts histones and opens the chromatin. We show that BRM is an epigenetically silenced gene in 10/11 Rhabdoid cell lines and in 70% of Rhabdoid tumors. Moreover, BRM can be induced by BAF47 re-expression and by Flavopiridol. By selective shRNAi knockdown of BRM, we show that BRM re-expression is necessary for growth inhibition by BAF47 re-expression or Flavopiridol application. Similar to lung cancer cell lines, we found that HDAC3, HDAC9, MEF2D and GATA3 controlled BRM silencing and that HDAC9 was overexpressed in Rhabdoid cancer cell lines. In primary BRM-deficient Rhabdoid tumors, HDAC9 was also found to be highly overexpressed. Two insertional BRM promoter polymorphisms contribute to BRM silencing, but only the -1321 polymorphism correlated with BRM silencing in Rhabdoid cell lines. To determine how these polymorphisms were tied to BRM silencing, we conducted ChIP assays and found that both HDAC9 and MEF2D bound to the BRM promoter at or near these polymorphic sites. Using BRM promoter swap experiments, we indirectly showed that both HDAC9 and MEF2D bound to these polymorphic sites. Together, these data show that the mechanism of BRM silencing contributes to the pathogenesis of Rhabdoid tumors and appears to be conserved among tumor types.     

Deregulation of MUC4 in gastric adenocarcinoma: potential pathobiological implication in poorly differentiated non-signet ring cell type gastric cancer

MUC4 is a large, heavily glycosylated transmembrane mucin, that is implicated in the pathogenesis of various types of cancers. To date, no extensive study has been done to check the expression and functional significance of MUC4 in different types of gastric adenocarcinomas. Here, we report the expression profile of MUC4 in gastric adenocarcinomas and its function in poorly differentiated gastric non-signet ring cell carcinoma (non-SRCC) type cells. Immunohistochemical analysis using tissue microarray (TMA) showed a significant difference in MUC4 expression between normal adjacent (n = 45) and gastric adenocarcinoma (n = 83; P < 0.001). MUC4 expression was not associated with tumour type, stage or with the degree of differentiation. To gain further insight into the significance of MUC4 expression in gastric non-SRCC cells, MUC4 was ectopically expressed in AGS, a poorly differentiated gastric non-signet ring cell line. The MUC4 overexpressing cells (AGS-MUC4) showed a significant increase (P < 0.005) in cell motility and a decrease in cellular aggregation as compared with the vector-transfected cells. Furthermore, in vivo tumorigenicity analysis revealed that animals transplanted with the MUC4 overexpressing cells (AGS-MUC4) had a greater incidence of tumours (83%) in comparison to empty vector control (17%). In addition, the expression of MUC4 resulted in enhanced expression of total cellular ErbB2 and phosphorylated ErbB2. In conclusion, our results showed that MUC4 is overexpressed in gastric adenocarcinoma tissues, and that it has a role in promoting aggressive properties in poorly differentiated gastric non-SRCC cells through the activation of the ErbB2 oncoprotein.     

Microsatellite instability and mismatch repair protein expressions in lymphocyte‐predominant breast cancer

The frequency of microsatellite instability (MSI) is reportedly extremely low in breast cancer, despite widespread clinical expectations that many patients would be responsive to immune‐checkpoint inhibitors (ICI). Considering that some triple‐negative breast cancers (TNBC) responded well to ICI in a clinical trial and that a high density of tumor‐infiltrating lymphocytes (TILs) is frequently observed in other cancers with high levels of microsatellite instability (MSI‐H), we hypothesized that some TNBC with a high density of TILs would be MSI‐H. Medullary carcinoma (MedCa) of the breast, a rare histological type, is characterized by a high density of TILs. Considering that MedCa of the colon is often MSI‐H, we suspected that MedCa in breast cancer might also include MSI‐H tumors. Therefore, we conducted MSI tests on such breast cancers with a high density of TILs. The MSI status of 63 TIL‐high TNBC and 38 MedCa tumors, all from Asian women who had undergone curative surgery, were determined retrospectively. DNA mismatch repair (MMR) proteins and PD‐L1 expression were also investigated immunohistochemically. All samples were microsatellite stable, being negative for all microsatellite markers. TIL‐high TNBC with low MLH1 protein had higher levels of PD‐L1 in stromal immune cells (P = .041). MedCa tumors showed significantly higher PD‐L1 expression in immune cells than in TIL‐high TNBC (<.001). We found that MSI‐H tumors were absent in TIL‐high breast cancers. Examination of MMR proteins, not a purpose of Lynch syndrome screening, may merit further studies to yield predictive information for identifying patients who are likely to benefit from ICI.     

Colorectal cancer intrinsic subtypes predict chemotherapy benefit,deficient mismatch repair and epithelial‐to‐mesenchymal transition

In most colorectal cancer (CRC) patients, outcome cannot be predicted because tumors with similar clinicopathological features can have differences in disease progression and treatment response. Therefore, a better understanding of the CRC biology is required to identify those patients who will benefit from chemotherapy and to find a more tailored therapy plan for other patients. Based on unsupervised classification of whole genome data from 188 stages I–IV CRC patients, a molecular classification was developed that consist of at least three major intrinsic subtypes (A‐, B‐ and C‐type). The subtypes were validated in 543 stages II and III patients and were associated with prognosis and benefit from chemotherapy. The heterogeneity of the intrinsic subtypes is largely based on three biological hallmarks of the tumor: epithelial‐to‐mesenchymal transition, deficiency in mismatch repair genes that result in high mutation frequency associated with microsatellite instability and cellular proliferation. A‐type tumors, observed in 22% of the patients, have the best prognosis, have frequent BRAF mutations and a deficient DNA mismatch repair system. C‐type patients (16%) have the worst outcome, a mesenchymal gene expression phenotype and show no benefit from adjuvant chemotherapy treatment. Both A‐type and B‐type tumors have a more proliferative and epithelial phenotype and B‐types benefit from adjuvant chemotherapy. B‐type tumors (62%) show a low overall mutation frequency consistent with the absence of DNA mismatch repair deficiency. Classification based on molecular subtypes made it possible to expand and improve CRC classification beyond standard molecular and immunohistochemical assessment and might help in the future to guide treatment in CRC patients.     

Genetic and clinical determinants of constitutional mismatch repair deficiency syndrome: Report from the constitutional mismatch repair deficiency consortium

BackgroundConstitutional mismatch repair deficiency (CMMRD) is a devastating cancer predisposition syndrome for which data regarding clinical manifestations, molecular screening tools and management are limited.MethodsWe established an international CMMRD consortium and collected comprehensive clinical and genetic data. Molecular diagnosis of tumour and germline biospecimens was performed. A surveillance protocol was developed and implemented.ResultsOverall, 22/23 (96%) of children with CMMRD developed 40 different tumours. While childhood CMMRD related tumours were observed in all families, Lynch related tumours in adults were observed in only 2/14 families (p = 0.0007). All children with CMMRD had café-au-lait spots and 11/14 came from consanguineous families. Brain tumours were the most common cancers reported (48%) followed by gastrointestinal (32%) and haematological malignancies (15%). Importantly, 12 (30%) of these were low grade and resectable cancers. Tumour immunohistochemistry was 100% sensitive and specific in diagnosing mismatch repair (MMR) deficiency of the corresponding gene while microsatellite instability was neither sensitive nor specific as a diagnostic tool (p < 0.0001). Furthermore, screening of normal tissue by immunohistochemistry correlated with genetic confirmation of CMMRD. The surveillance protocol detected 39 lesions which included asymptomatic malignant gliomas and gastrointestinal carcinomas. All tumours were amenable to complete resection and all patients undergoing surveillance are alive.DiscussionCMMRD is a highly penetrant syndrome where family history of cancer may not be contributory. Screening tumours and normal tissues using immunohistochemistry for abnormal expression of MMR gene products may help in diagnosis and early implementation of surveillance for these children.     

Establishment and characterization of MRT cell lines from genetically engineered mouse models and the influence of genetic background on their development

Malignant rhabdoid tumors (MRTs) are rare, aggressive cancers occuring in young children primarily through inactivation of the SNF5(INI1, SMARCB1) tumor suppressor gene. We and others have demonstrated that mice heterozygous for a Snf5 null allele develop MRTs with partial penetrance. We have also shown that Snf5^+/? mice that lack expression of the pRb family, due to TgT₁₂₁ transgene expression, develop MRTs with increased penetrance and decreased latency. Here, we report that altering the genetic background has substantial effects upon MRT development in Snf5^+/?‐ and TgT₁₂₁;Snf5^+/? mice, with a mixed F1 background resulting in increased latency and the appearance of brain tumors. We also report the establishment of the first mouse MRT cell lines that recapitulate many features of their human counterparts. Our studies provide further insight into the genetic influences on MRT development as well as provide valuable new cell culture and genetically engineered mouse models for the study of CNS‐MRT etiology.     

Differences in the immunosurveillance pattern associated with DNA mismatch repair status between right‐sided and left‐sided colorectal cancer

Tumor location and immunity play important roles in the progression of colorectal cancer (CRC). This study aimed to investigate the differences in the immunosurveillance pattern between right‐ and left‐sided CRC and analyze their association with clinicopathologic features, including mismatch repair (MMR) status. We included surgically resected stage II/III CRC cases and evaluated the immunohistochemical findings of HLA class I, HLA class II, programmed cell death‐ligand 1 (PD‐L1), PD‐1, CTLA‐4, CD3, CD4, CD8, TIA‐1, T‐bet, GATA3, RORγT, Foxp3, and CD163. A total of 117 patients were included in the analyses; of these, 30 and 87 had right‐ and left‐sided cancer, respectively. Tumor immunity varied according to the tumor location in the overall cohort. Analysis of the tumors excluding those with DNA mismatch repair (MMR) deficiency also revealed that tumor immunity differed according to the tumor location. In right‐sided colon cancer (CC), high expression of Foxp3 (P = .0055) and TIA‐1 (P = .0396) were associated with significantly better disease‐free survival (DFS). High CD8 (P = .0808) and CD3 (P = .0863) expression tended to have better DFS. Furthermore, in left‐sided CRC, only high PD‐L1 expression in the stroma (P = .0426) was associated with better DFS. In multivariate analysis, high Foxp3 expression in right‐sided CC was an independent prognostic factor for DFS (hazard ratio, 7.6445; 95% confidence interval, 1.2091‐150.35; P = .0284). In conclusion, the immunosurveillance pattern differs between right‐ and left‐sided CRC, even after adjusting for MMR deficiency.