Microsatellite Instability Characteristics Research Articles

PAIP 2020: Microsatellite instability prediction in colorectal cancer.

Microsatellite instability (MSI) refers to alterations in the length of simple repetitive genomic sequences. MSI status serves as a prognostic and predictive factor in colorectal cancer. The MSI-high status is a good prognostic factor in stage II/III cancer, and predicts a lack of benefit to adjuvant fluorouracil chemotherapy in stage II cancer but a good response to immunotherapy in stage IV cancer. Therefore, determining MSI status in patients with colorectal cancer is important for identifying the appropriate treatment protocol. In the Pathology Artificial Intelligence Platform (PAIP) 2020 challenge, artificial intelligence researchers were invited to predict MSI status based on colorectal cancer slide images. Participants were required to perform two tasks. The primary task was to classify a given slide image as belonging to either the MSI-high or the microsatellite-stable group. The second task was tumor area segmentation to avoid ties with the main task. A total of 210 of the 495 participants enrolled in the challenge downloaded the images, and 23 teams submitted their final results. Seven teams from the top 10 participants agreed to disclose their algorithms, most of which were convolutional neural network-based deep learning models, such as EfficientNet and UNet. The top-ranked system achieved the highest F1 score (0.9231). This paper summarizes the various methods used in the PAIP 2020 challenge. This paper supports the effectiveness of digital pathology for identifying the relationship between colorectal cancer and the MSI characteristics.

Microsatellite instability in Chinese gastric cancer and its correlation with clinical characteristics.

Microsatellite instability (MSI) remains a focus of interest in cancer research, but the characteristics of MSI in gastric cancer (GC) are ambiguous. In this retrospective study, we analyzed the prevalence of MSI and the expression of programmed death-ligand 1 (PD-L1) and cluster of differentiation 8 (CD8) cells in Chinese GC patients. A total of 393 GC patients admitted to two centers from January 2010 to December 2017 were enrolled. The prevalence of MSI in this cohort was 3.4% and most frequently occurred in females, patients aged between 59 and 69 years, and patients at a lower clinical stage. All MSI GCs had CD8 expression but lacked PD-L1 expression, indicating that MSI was related to CD8 expression but irrelevant to PD-L1 expression. However, there was no significant difference in the expression of CD8/PD-L1 between MSI GC and microsatellite stable (MSS) GC. Kaplan-Meier survival curves revealed that patients with MSI had a significantly longer overall survival (OS) than patients with MSS. In Chinese GC patients, MSI frequently occurred in females, patients aged between 59 and 69, and patients with lower clinical stages. Patients with MSI-High (MSI-H) and MSI-Low (MSI-L) had a longer OS than patients with MSS. MSI was related to CD8 expression but irrelevant to PD-L1 expression.

Triple-Negative Breast Cancer: Intact Mismatch Repair and Partial Co-Expression of PD-L1 and LAG-3.

Background and AimPoor response to immune checkpoint inhibitors (ICIs) has been observed in most triple-negative breast cancer (TNBC) cases (around 80%). Our aim was to investigate the status of mismatch repair (MMR), microsatellite instability (MSI), programmed death-ligand 1 (PD-L1), and lymphocyte-activation gene 3 (LAG-3) in TNBC.MethodsA total of 74 TNBC samples were retrospectively analyzed. MMR and MSI were evaluated by immunohistochemistry (IHC) and polymerase chain reaction (PCR) using Promega 1.2 and NCI panels, respectively. PD-L1, LAG-3, and CD8 expression was assessed by IHC.ResultsNone of the cases demonstrated deficient MMR (dMMR) or MSI. In total, 43/74 cases (58.1%) were PD-L1+, including 1 tumor PD-L1+, 25 tumor-infiltrating lymphocytes (TILs) PD-L1+, and 17 cases involving concurrence of tumor and TIL PD-L1+. The rate of TIL PD-L1+ was remarkably higher than that of tumor PD-L1+ (P<0.001). We identified 20 LAG-3+ cases (27.0%, 20/74), all of which were PD-L1+. Co-expression of PD-L1 and LAG-3 was noted in 46.5% (20/43) of the PD-L1+ population. In the LAG-3+ subtype (co-expression of PD-L1 and LAG-3), high correlation between TILs PD-L1+ and LAG-3+ was observed (P<0.01). A high frequency of CD8+ (98.6%, 73/74) was observed.ConclusiondMMR/MSI characteristics may not be a practical predictive marker for ICIs in TNBC. PD-L1+ is more common in TILs than in tumors. In the PD-L1+ population, approximately half of the cases showed LAG-3 co-expression. For patients with a poor response to PD-1(L1) mono ICI, dual blockade of PD-1(L1) and LAG-3 may be a viable option for the management of TNBC.

Abstract 2650: Clinical implication of microsatellite instability in early gastric cancer

Abstract Purpose: The role of microsatellite instability is well established in advanced gastric cancer. However, its clinical implication has not been well addressed in early gastric cancer. The purpose of this study is to evaluate the clinical characteristics of microsatellite instability in early gastric cancer. Methods: Patients who underwent gastrectomy with curative intent in Severance hospital from January, 2005 to December, 2010 and diagnosed as early gastric cancer (pT1a/b) were enrolled in this study. Remnant gastric cancer and patients who received chemotherapy before operation were excluded. Microsatellite instability status was evaluated by two mononucleotide repeat markers (BAT25 and BAT26) and three dinucleotide repeat markers (D5S346, D2S123, and D17S250) and instability in two or more markers was defined as miscrosatellite instability high (MSI-H), otherwise classified as microsatellite stable (MSS). Results: Of 1156 tumors that included the final analysis, 85 (7.4%) were MSI-H. MSI-H cancer was related to frequent female gender (54.1% vs. 32.8%, p&amp;lt;0.001), older age (63.4 ± 10.65 vs. 56.7 ± 11.50, p&amp;lt;0.001), lower body (81.2% vs. 59.7%, p=0.002), intestinal histology (63.5% vs. 48.2%, p=0.005), lympho-vascular invasion (25.9% vs. 13.3%, p=0.001), submucosal invasion (63.5% vs. 48.3%, p=0.007), and trend of lymph node metastasis (17.6% vs. 10.8%, p=0.056) compared to MSS type. Lymph node metastasis and lymph-vascular invasion was not differed by MSI status in mucosal gastric cancer (3.2% vs. 2.3%, p=0.755 and 3.2% vs. 2.3%, p=0.755, respectively). In sumbucosal gastric cancer, however, lympho-vascular invasion was frequently observed in MSI-H tumor (38.9% vs. 25.0%, p=0.027) but there was no difference in lymph node metastasis (25.9% vs. 19.9%, p=0.298). When we compared the disease free survival by MSI status, the prognosis of MSI-H tumor was similar compared to that of MSS tumor (log-rank test p=0.797, adjusted Hazard ratio of MSI-H by age, sex, pTstage and number of metastatic LNs: 0.932 [95% confidence interval: 0.423-2.054, p=0.861]). Conclusions: MSI status could not be a useful biomarker in early gastric cancer to predict prognosis of it. However, frequent lympho-vascular invasion of MSI-H early gastric cancer would be a warning that careful patient's selection for endoscopic treatment or limited lymph node dissection for surgery is necessary. Citation Format: Yoon Young Choi, Dong Gyu Kim, Taeil Son, Hyoung-Il Kim, Jae-Ho Cheong, Woo Jin Hyung, Sung Hoon Noh. Clinical implication of microsatellite instability in early gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2650.