Role of Mismatch Repair Deficiency Status and Microsatellite Instability in Relation to the Expression of Immune Checkpoint Proteins in Colorectal Cancer

Introduction Colorectal cancer (CRC) is the third most common cancer in the world among men and second among women worldwide. One of the major molecular pathways responsible for the development of colorectal cancer (CRC) is the microsatellite instability (MSI) pathway. During carcinogenesis, the tumor cells express programmed death ligand-1 (PD-L1), which reduces the immunogenicity leading to the escape of immune attack. Anti-PD-L1 interaction is an upcoming line of research for the treatment of colorectal carcinoma patients. Materials and methods The present study was an ambispective study where the mismatch repair deficiency status (MMR) and programmed death ligand-1 (PD-L1) expression were studied using immunohistochemistry and then later analyzed and compared with the clinicopathological parameters and MSI status in relation to the expression of programmed death ligand-1 (PD-L1) in neoplastic and immune cells in a total of 55 biopsy specimen. MMR expression was reported as retained or loss of nuclear staining, and PD-L1 expression was taken as positive with a cut-off of more than or equal to 5% membranous positivity in both tumor cells and immune cells. Results The analysis showed a significant correlation of microsatellite instability (MSI) status with two of the clinicopathological parameters, which were the site of the tumor (p-value<0.001) and M stage (p-value<0.001). PD-L1 expression in neoplastic cells showed no significant correlation with the clinicopathological parameters, whereas PD-L1 expression in immune cells showed a significant association with gender (p-value=0.043). Also, MSI status showed a significant association with PD-L1 expression in tumor cells (p-value <0.001).

Early-Onset/Young-Onset Colorectal Carcinoma: A Comparative Analysis of Morphological Features and Biomarker Profile

Introduction Colorectal carcinoma (CRC) is one of the most common cancers that involve the human body. Young-onset CRC (YO-CRC) or early-onset CRC (EO-CRC) is defined as CRC that develops before the age of 50 years, as opposed to CRC that is diagnosed after the age of 50, referred to as late-onset CRC (LO-CRC). EO-CRC is sparsely studied in our population. Therefore, in this study, we evaluated the clinicopathological parameters and biomarker profile of EO-CRC and compared them with those of LO-CRC. Methods This was a retrospective study conducted at the Department of Histopathology, Liaquat National Hospital, Karachi, Pakistan. A total of 254 biopsy-proven cases of CRC, reported over a period of nine years, were enrolled in the study. The specimens collected during surgery were sent to the laboratory for histopathological and immunohistochemical (IHC) status examinations. IHC staining of the specimens was performed using antibodies, namely, MutL protein homolog 1 (MLH1), postmeiotic segregation increased 2 (PMS2), MutS homolog 2 (MSH2), MutS homolog 6 (MSH6), and human epidermal growth factor receptor 2 (HER2/neu), on representative tissue blocks. A comparison of morphological and biomarker profiles between EO-CRC and LO-CRC was performed. Results The mean age at diagnosis was 46.27±17.75 years, with female predominance (59.8%). A significant difference between the two groups (EO-CRC and LO-CRC) was noted with respect to laterality, tumor site, tumor grade, tumor type, presence of pre-existing polyps, perineural invasion (PNI), lymphovascular invasion (LVI), and IHC markers. EO-CRC (as opposed to LO-CRC) significantly affected the left colon (92.6% vs. 72.9%, p<0.001), with the rectosigmoid being the most common site in the majority of cases (72.1% in EO-CRC vs. 61% in LO-CRC). EO-CRC showed a higher frequency of PNI and LVI than LO-CRC (42.6% vs. 23.7%, p=0.001; 29.4% vs. 18.6%, p=0.046, respectively). A significantly higher proportion of EO-CRCs were mucinous (42.6%) and medullary carcinoma (11.8%). Although the majority (54.4%) of cases of EO-CRC were grade 2 tumors at the time of diagnosis, a significantly higher proportion of them were grade 3 (44.1%) compared with LO-CRC. IHC comparisons between the two age groups showed that a significantly higher proportion of cases of EO-CRC showed positive HER2/neu expression (27.1%) compared with LO-CRC (13.2%). Conversely, the loss of expression of microsatellite instability (MSI) markers was more commonly seen in LO-CRS compared with EO-CRC. Conclusions We found a relatively higher frequency of EO-CRC in our population. Moreover, compared with LO-CRCs, EO-CRCs were associated with prognostically poor histological parameters, such as mucinous and medullary carcinoma, high-grade, PNI, and LVI. Similarly, EO-CRC had a higher positive expression of HER2/neu with intact MSI markers compared with AO-CRC; all these characteristics indicate poor biological behavior in EO-CRC.

RAS genes in colorectal carcinoma: pathogenesis, testing guidelines and treatment implications

The RAS family is among the most commonly mutated genes in all human malignancies including colon cancer. In normal cells, RAS proteins act as a link in the intracellular signal transduction initiated by binding of growth factors to cell membrane receptors mediating cell survival. RAS isoproteins have great morphological similarities, but despite that, they are thought to have different functions in different tissues. RAS mutations, as supported by several studies including animal models, have a role in the development and progression of colorectal cancer. The detection of RAS mutations in patients with colorectal carcinoma, specifically KRAS and NRAS, has significant clinical implications. It is currently recommended that patients with colon cancer who are considered for antiepidermal growth factor receptor monoclonal antibodies, get RAS mutation testing since only those with wildtype-RAS genes benefit from such treatment. Despite decades of research, there is currently no effective and safe treatment that directly targets RAS-mutated neoplasms. Multiple therapeutic approaches directed against RAS mutations are currently experimental, including a promising immunotherapy study using T-cells in patients with metastatic colon cancer.

Allelic imbalance in 1p, 7q, 9p, 11p, 12q and 16q regions in non-small cell lung carcinoma and its clinical association: a pilot study

In lung cancer pathogenesis, genetic instability, i.e., loss of heterozygosity (LOH) and microsatellite instability (MSI) is a frequent molecular event, occurring at an early stage of cancerogenesis. The presence of LOH/MSI in non-small cell lung carcinoma (NSCLC) was found in many chromosomal regions, but exclusive of 3p their diagnostic value remains controversial. In this study we focused on other than 3p regions-1p31.2, 7q32.2, 9p21.3, 11p15.5, 12q23.2 and 16q22-the loci of many oncogenes and tumour suppressor genes. To analyze the potential role of LOH/MSI involved in NSCLC pathogenesis we allelotyped a panel of 13 microsatellite markers in a group of 56 cancer specimens. Our data demonstrate the presence of allelic loss for all (13) analyzed markers. Total LOH/MSI frequency in NSCLC was the highest for chromosomal region 11p15.5 (25.84 %), followed by 9p21.3 and 1p31.2 (19.87 and 16.67 % respectively). A statistically significant increase of total LOH/MSI frequency was detected for the 11p15.5 region (p = 0.0301; χ(2) test). The associations of total LOH/MSI frequency: 1) increase in 11p15.5 region (p = 0.047; χ(2) test) and 2) decrease in 7q32.2 region (p = 0.037; χ(2) test) have been statistically significant in AJCC III (American Joint Committee on Cancer Staging). In Fractional Allele Loss (FAL) index analysis, the correlation with cigarette addiction has been statistically significant. The increased amount of cigarettes smoked (pack years) in a lifetime correlates with increasing FAL (p = 0.024; Kruskal-Wallis test). These results demonstrate that LOH/MSI alternation in studied chromosomal regions is strongly influenced by tobacco smoking but do not seem to be pivotal NSCLC diagnostic marker with prognostic impact.

Leukocyte infiltrate in gastrointestinal adenocarcinomas is strongly associated with tumor microsatellite instability but not with tumor immunogenicity

PURPOSE

To analyze the correlation of genomic instability with leukocyte infiltrate in gastrointestinal carcinomas (GIACs) and with tumor immunogenicity, e.g., HLA class I cell surface expression defects and galectin-3 and PDL-1 expression.

EXPERIMENTAL DESIGN

Lymphocyte and macrophage infiltrations were immunohistochemically studied in HLA class I negative GIACs with sporadic high-level microsatellite instability (MSI-H) or microsatellite stability (MSS).

RESULTS

Tumors with MSI-H were associated with the following: dense infiltration (CD45, P < 0.001); cytotoxic CD8-positive lymphocytes (P < 0.001); and a complete absence of HLA class I cell surface expression, due to inactivating β2-microglobulin (β2-m) mutation in 50% of cases. In contrast, HLA class I negative tumors with MSS were significantly associated with fewer CD8-positive lymphocytes. There was no association between microsatellite instability and other molecular features of the tumor cells, including expression of galectin-3. Finally, macrophage infiltrate in the tumors was not correlated with microsatellite instability or HLA class I cell surface expression (CD64, P = 0.63; CD163, P = 0.51).

CONCLUSIONS

Microsatellite instability appears to be the most important factor determining the composition, density, and localization of leukocyte infiltrate, which is independent of other molecular features such expression of HLA class I cells, galectin-3, or programmed death ligand-1. Accordingly, the strong intratumoral CD8+ T infiltration of MSI-H tumors may be produced by elevated levels of specific inflammatory chemokines in the tumor microenvironment.

Frameshift mutations and a length polymorphism in the hMSH3 gene and the spectrum of microsatellite instability in sporadic colon cancer

Mutations in the hMVSH3 gene in sporadic colon cancer with microsatellite instability (MSI) were investigated, since several mismatch repair genes were known to be mutated in cancers with MSI, but only deletions in the (A)8 region in the hMSH3 gene have been reported. We also analyzed the relationships between hMSH3 mutations and the spectrum of MSI. We screened MSI in 79 sporadic colon cancer samples using mono- and dinucleotide repeat markers and the samples with MSI were further analyzed for tri- and tetranucleotide repeat instability and mutations in the hMSH3 gene by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. Five (6%) out of 79 tumors were MSI-H and 15 (19%) were MSI-L. Two MSI-H tumors showed insertion in the (C)8 region in the hMSH6 gene and one tumor showed insertion and deletion in the (A)8 region in the hMSH3 gene, and two of the three above tumors showed MSI in tri-and tetranucleotide repeats. One MSI-L tumor showed somatic alteration in a 9-bp repeat sequence in hMSH3. No frameshift mutations were found in the (A)7 and (A)6 regions in hMSH3. Thus, we confirmed that the (A)8 region in hMSH3 is a hot spot and mutations in the (A)7 and (A)6 regions in hMSH3 are not common. The hMSH3 mutation may enhance genomic instability in some colorectal cancers.

Microsatellite instability in sporadic colorectal cancer is not an independent prognostic factor

Hereditary non-polyposis colorectal cancer (HNPCC) is linked to an inherited defect in the DNA mismatch repair system. DNA from HNPCC tumours shows microsatellite instability (MSI). It has been reported that HNPCC patients have a better prognosis than patients with sporadic colorectal cancer. We examined whether the presence of MSI in a series of unselected colorectal tumours carries prognostic information. In a series of 181 unselected colorectal tumours, 22 tumours (12%) showed MSI. Survival analysis at 5-10 years follow-up showed no statistically significant difference in prognosis between MSI-positive and -negative tumours. Our results suggest that the MSI phenotype as such is not an independent prognostic factor.