High-level microsatellite instability is not involved in gallbladder carcinogenesis

Expression of HER2 and Mismatch Repair Proteins in Surgically Resected Gallbladder Adenocarcinoma

Background

Gallbladder cancer (GBC) has a poor prognosis. Although complete surgical resection is the only successful approach for improving survival, additional therapeutic modalities are required for recurrent or surgically unresectable GBCs.

Materials and Methods

To determine the expression status of HER2 and the mismatch repair (MMR) proteins MLH1, MSH2, MSH6, and PMS2, immunohistochemical staining of MMR proteins and HER2 was carried out in 216 surgically resected GBCs. HER2 labeling was scored by adopting a scoring system for gastric carcinomas. Tissues scoring 0 to 2+ were defined as HER2 negative, whereas those scoring 3+ were regarded as HER2-positive. In addition, silver in situ hybridization and microsatellite instability (MSI) analysis were conducted to confirm HER2 amplification and MSI, respectively.

Results

Three of 216 GBCs (1.3%) showed MMR protein deficiency. All three observed MSI cases exhibited dual loss of MSH2 and MSH6 protein expression. However, no cases showed loss of either MLH1 or PMS2 expression. No association was observed between MMR protein deficiency and other clinicopathological factors. HER2 amplification was noted in 30 (13.9%) GBCs and associated with Crohn-like lymphoid reaction (P = 0.023). No survival difference was observed based on HER2 overexpression or HER2 amplification status.

Conclusion

MMR protein deficiency and HER2 overexpression were observed in a small subset (1.3% and 13.9%, respectively) of GBCs without simultaneous occurrence of deficient MMR protein expression and HER2 overexpression. The presence of Crohn-like lymphoid reaction may help identify cases with HER2 amplification, by using hematoxylin-stained slides. Although the proportion of MMR protein-deficient- and HER2-overexpressing GBCs was small, applying immunotherapy to MMR protein-deficient GBCs and herceptin to HER2-overexpressing GBCs may provide alternative treatment options for patients with GBC.

DNA Mismatch Repair Deficiency and Immune Checkpoint Inhibitors in Gastrointestinal Cancers

In the recent few years, significant efforts have been undertaken for the development of different immunotherapeutic approaches against cancer. In this context, immune checkpoint inhibitors (ICIs), a novel class of immunotherapeutic drugs with the potential to unleash the immune system, have emerged as authentic game-changers for managing patients with various cancers, including gastrointestinal malignancies. Although the majority of gastrointestinal cancers are generally considered poorly immunogenic, basic research findings and data from clinical trials have proven that subset(s) of patients with various digestive tract cancers are highly responsive to ICI-based therapy. In this context, a better understanding on the role of various DNA repair pathway alterations, especially the evidence supporting the significant importance of DNA mismatch repair deficiencies and the efficacy of the anti-programmed cell death 1 drugs, have led to US Food and Drug Administration approval of 2 anti-programmed cell death 1 antibodies (pembrolizumab and nivolumab) for the treatment of patients with microsatellite instability. This review aims to provide a comprehensive and up-to-date summary for the role of DNA mismatch repair deficiency in cancer, and its importance in the development of ICI therapy. In addition, we provide insights into the spectrum of various genetic alterations underlying ICI resistance, together with the important influence that the tumor microenvironment plays in mediating the therapeutic response to this new class of drugs. Finally, we provide a comprehensive yet succinct glimpse into the most exciting preclinical discoveries and ongoing clinical trials in the field, highlighting bench-to-beside translational impact of this exciting area of research.

Inflammation-associated microsatellite alterations: Mechanisms and significance in the prognosis of patients with colorectal cancer

Microsatellite alterations within genomic DNA frameshift as a result of defective DNA mismatch repair (MMR). About 15% of sporadic colorectal cancers (CRCs) manifest hypermethylation of the DNA MMR gene MLH1, resulting in mono- and di-nucleotide frameshifts to classify it as microsatellite instability-high (MSI-H) and hypermutated, and due to frameshifts at coding microsatellites generating neo-antigens, produce a robust protective immune response that can be enhanced with immune checkpoint blockade. More commonly, approximately 50% of sporadic non-MSI-H CRCs demonstrate frameshifts at di- and tetra-nucleotide microsatellites to classify it as MSI-low/elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) as a result of functional somatic inactivation of the DNA MMR protein MSH3 via a nuclear-to-cytosolic displacement. The trigger for MSH3 displacement appears to be inflammation and/or oxidative stress, and unlike MSI-H CRC patients, patients with MSI-L/EMAST CRCs show poor prognosis. These inflammatory-associated microsatellite alterations are a consequence of the local tumor microenvironment, and in theory, if the microenvironment is manipulated to lower inflammation, the microsatellite alterations and MSH3 dysfunction should be corrected. Here we describe the mechanisms and significance of inflammatory-associated microsatellite alterations, and propose three areas to deeply explore the consequences and prevention of inflammation's effect upon the DNA MMR system.

Mismatch Repair Deficiency and Response to Immune Checkpoint Blockade

: More than 1.6 million new cases of cancer will be diagnosed in the U.S. in 2016, resulting in more than 500,000 deaths. Although chemotherapy has been the mainstay of treatment in advanced cancers, immunotherapy development, particularly with PD-1 inhibitors, has changed the face of treatment for a number of tumor types. One example is the subset of tumors characterized by mismatch repair deficiency and microsatellite instability that are highly sensitive to PD-1 blockade. Hereditary forms of cancer have been noted for more than a century, but the molecular changes underlying mismatch repair-deficient tumors and subsequent microsatellite unstable tumors was not known until the early 1990s. In this review article, we discuss the history and pathophysiology of mismatch repair, the process of testing for mismatch repair deficiency and microsatellite instability, and the role of immunotherapy in this subset of cancers.

IMPLICATIONS FOR PRACTICE

Mismatch repair deficiency has contributed to our understanding of carcinogenesis for the past 2 decades and now identifies a subgroup of traditionally chemotherapy-insensitive solid tumors as sensitive to PD-1 blockade. This article seeks to educate oncologists regarding the nature of mismatch repair deficiency, its impact in multiple tumor types, and its implications for predicting the responsiveness of solid tumors to immune checkpoint blockade.

Mismatch Repair Deficiency and Response to Immune Checkpoint Blockade

: More than 1.6 million new cases of cancer will be diagnosed in the U.S. in 2016, resulting in more than 500,000 deaths. Although chemotherapy has been the mainstay of treatment in advanced cancers, immunotherapy development, particularly with PD-1 inhibitors, has changed the face of treatment for a number of tumor types. One example is the subset of tumors characterized by mismatch repair deficiency and microsatellite instability that are highly sensitive to PD-1 blockade. Hereditary forms of cancer have been noted for more than a century, but the molecular changes underlying mismatch repair-deficient tumors and subsequent microsatellite unstable tumors was not known until the early 1990s. In this review article, we discuss the history and pathophysiology of mismatch repair, the process of testing for mismatch repair deficiency and microsatellite instability, and the role of immunotherapy in this subset of cancers.

IMPLICATIONS FOR PRACTICE

Mismatch repair deficiency has contributed to our understanding of carcinogenesis for the past 2 decades and now identifies a subgroup of traditionally chemotherapy-insensitive solid tumors as sensitive to PD-1 blockade. This article seeks to educate oncologists regarding the nature of mismatch repair deficiency, its impact in multiple tumor types, and its implications for predicting the responsiveness of solid tumors to immune checkpoint blockade.

Targeted Therapy in Biliary Tract Cancers

OPINION STATEMENT

A paradigm shift towards molecular-based, personalized cancer therapeutics has occurred in recent years and a number of targeted drugs have emerged. Various targeted therapies like erlotinib, trastuzumab, and cetuximab have been approved in lung, breast, and colon cancers, respectively. Numerous clinical trials involving targeted drugs in biliary tract cancers are currently in progress, though none have been approved for this disease. Biliary tract cancers are divided into separate entities both anatomically and in terms of pathogenesis but are grouped together in most trials given their rarity. Combination chemotherapy involving cisplatin and gemcitabine is the current standard of care in the metastatic setting. In this review, we will discuss the various molecular pathways implicated in biliary tract cancers and potential therapeutic targets.

Microsatellite instability in gallbladder carcinoma

The genetic abnormalities involved in the pathogenesis of gallbladder carcinoma (GBC) remain unclear. Microsatellite instability (MSI) has been described in many carcinomas, but little is known about the significance of mismatch repair in gallbladder carcinogenesis. Additionally, methylation status of long interspersed element-1 (LINE-1), a surrogate marker of global DNA methylation, has defined distinct subsets of other cancer types but has not been explored in GBC. Immunohistochemical expression of MSH2, MSH6, MLH1, and PMS2 and LINE-1 mRNA in situ hybridization was evaluated in 67 primary and 15 metastatic GBCs from 77 patients. Amplification of human epidermal growth factor receptor 2 (HER2) was evaluated by fluorescence in situ hybridization. Genotyping for 24 genes involved in carcinogenesis was performed using a multiplex PCR-based platform. MSI was present in 6 of 77 GBCs (7.8 %). Loss of MSH2/MSH6 was detected in five cases and loss of MLH1/PMS2 in one case. MSI status was not associated with Lynch syndrome, tumor grade, extracellular mucin, or tumor-infiltrating lymphocytes. There was no significant difference in mean overall survival of patients with and without MSI. Strong LINE-1 staining was identified in none of the GBC with MSI and in 36 of 69 (52 %) of those without MSI (p = 0.005), suggesting that LINE-1 in the former cohort was hypermethylated. All MSI tumors were negative for HER2 amplification, and TP53 and NRAS mutations were only found in GBC without MSI. MSI was identified in a minority of GBC cases. The strong correlation between global DNA methylation as measured by LINE-1 and loss of mismatch repair proteins suggests that methylation may account for the loss of these proteins. These hypermethylated tumors appear to represent a genetically unique cohort of gallbladder neoplasms, and the data suggests that demethylating agents may have a therapeutic value in this class of tumors.

The analysis of microsatellite instability in extracolonic gastrointestinal malignancy

Microsatellite instability (MSI) is a genetic feature of sporadic and familial cancers of multiple sites and is related to defective mismatch repair (MMR) protein function. Lynch syndrome (LS) is a familial form of MMR deficiency that may present with a spectrum of MSI positive cancers including gastrointestinal (GI) malignancies. The incidence of high level MSI (MSI-H) in colorectal carcinoma is well defined in both familial and sporadic cases and these tumours portend a better overall prognosis in colorectal carcinoma (CRC). There are certain morphological features that suggest MSI-H CRC and international guidelines have been established for the evaluation of MSI in CRC. The prevalence and morphological features of extracolonic GI MSI-H tumours are less well documented. Furthermore, it is unclear whether the guidelines for the assessment of MSI in CRC are appropriate for application to extracolonic GI malignancies. This review aims to summarise the recent literature on MSI in extracolonic LS-related GI tract malignancies with special attention to the assessment of the MMR system by evaluation of specific microsatellite markers and/or immunohistochemical evaluation of MMR protein expression. The reported prevalence of sporadic and LS-related MSI-H tumours along with their associated unique morphological patterns and related prognostic or therapeutic implications will be discussed.

Genetic changes of p53, K-ras, and microsatellite instability in gallbladder carcinoma in high-incidence areas of Japan and Hungary

AIM: To disclose geographic differences in genetic changes involved in gallbladder carcinogenesis between two distinct high-incidence areas of Japan and Hungary.

METHODS: We examined 42 cases of gallbladder carcinoma: 22 Japanese and 20 Hungarian cases. p53 mutations at exons 5 to 8 and K-ras mutations at codon 12 were tested by direct sequencing. Microsatellite instability was determined from fluorescent dye-labeled PCR amplifications of five-microsatellite markers (BAT-25, BAT-26, D2S123, D5S346, and D17S250).

RESULTS: Mutations of p53 were detected in 11 of 22 Japanese cases and 6 of 18 Hungarian cases (11/22 vs 6/18, P = 0.348). Transition at CpG sites was found in none of 11 Japanese cases and 2 of 6 Hungarian cases; the difference was marginally significant (0/11 vs 2/6, P = 0.110). K-ras mutations were detected in only one of the Hungarian cases. Eight of 19 (42.1%) Japanese cases were MSI-high (presence of novel peaks in more than one of the five loci analyzed), whereas only 1 of 15 (6.7%) Hungarian cases was MSI-high (P = 0.047).

CONCLUSION: It appears that the p53 mutations and MSI differ in patients with gallbladder carcinoma between two distinct high-incidence areas. Geographic variation might exist in the process of gallbladder carcinogenesis.

Simultaneous gallbladder and bile duct cancers: revisiting the pathological possibilities

The pathogenesis of gallbladder cancer presenting synchronously with malignancy of the bile duct has not been clearly understood. The possible causes for the simultaneous presence of these tumors could be due to local spread, metastases, de novo multifocal origin, or as part of a field change in the extrahepatic biliary apparatus. In this article, we discuss the cases of four patients with simultaneous gallbladder and bile duct malignancies and analyze their individual pathologies to provide an explanation into the mechanisms that may play a role in such conditions.

Lack of association between microsatellite instability and benign adrenal tumors

BACKGROUND

The adrenal gland may give rise to pheochromocytomas, which are catecholamine-producing tumors originating from the adrenal medulla, or to adrenocortical tumors, which derive from the adrenocortical cortex and may be secreting or not. The genetic mechanisms underlying the formation of these tumors include somatic mutations in susceptibility genes, especially in the familial forms, and allelic loss, especially in chromosome 1.

AIM

The aim of this study was to investigate a third genetic mechanism by evaluating microsatellite instability using the reference markers (Bat25, Bat26, D2S123, D5S346, D17S250) validated by the National Cancer Institute. Microsatellite loci were analyzed in 32 benign tumors, including 11 pheochromocytomas and 21 adrenocortical tumors, in patients with and without familial syndrome.

RESULTS

The different alleles of microsatellite loci were reliably detected by DNA fragments analysis, whereas data obtained after melting-point analysis on the Lightcycler were inconsistent. No microsatellite instability was detected in any tumor. One patient with a unilateral pheochromocytoma showed a loss of heterozygosity for D17S250. A second patient with a MEN-2A syndrome and a two-sided pheochromocytoma exhibited a loss of heterozygosity for D2S123 in the right tumor only and a retention of heterozygosity for all markers in the left tumor.

CONCLUSIONS

These results suggest that microsatellite instability, evaluated by the five reference markers of the National Cancer Institute, is not a feature of benign adrenal tumors.

K-ras, p53 mutations, and microsatellite instability (MSI) in gallbladder cancer

Despite the considerable progress in understanding the molecular pathology of carcinogenesis, the genetic mechanisms underlying the development and progression of gallbladder cancer (GC) are poorly understood. The survival of GC patients is generally poor. Therefore, it is very useful to define valuable prognostic factors. The most extensively studied oncogenes in gallbladder carcinogenesis are ras, commonly mutated in neoplasms of the gastrointestinal tract. K-ras oncogene is altered in a subset of gallbladder patients and mainly in those having anomalous junction of the pancreaticobiliary tract. Most of the studies of genetic abnormalities in GC have focused on p53 gene. p53 mutation/overexpression and/or LOH is present in more than 50% of gallbladder carcinomas, suggesting an important role in their pathogenesis. However, these results have not any predictive value yet. Moreover, the involvement of an alternative molecular pathway, that of microsatellite instability (MSI), is found in a limited group of GC patients. Additional research is necessary to establish its possible relation to defects of the mismatch repair (MMR) system and its proposed prognostic significance. Further elucidation of the molecular events specific to GC will help to identify novel molecular targets for the diagnosis and clinical management of the patients.