The distribution of intratumoral macrophages correlates with molecular phenotypes and impacts prognosis in colorectal carcinoma.

AIMS: The role of tumour-associated macrophages (TAMs) in colorectal cancer (CRC) remains elusive. In this study, we aimed to examine the correlation between TAMs, clinicopathological features, tumour-infiltrating lymphocytes (TILs) and prognosis in CRC by the use of image analysis. METHODS AND RESULTS: Immunohistochemical staining for CD68 and CD163 was performed as pan-macrophage and M2-macrophage markers, respectively. Each marker was analysed separately for intra-epithelial and stromal area densities. All four macrophage densities showed a significant correlation with one another (P = 0.001). Intra-epithelial CD68+ macrophage densities showed a correlation with pTNM stage (P = 0.008), microsatellite instability (MSI) (P < 0.001), CpG island methylator phenotype (CIMP) (P < 0.001) and TIL densities (P < 0.001). Intra-epithelial CD163+ macrophage densities were associated with perineural invasion, MSI, CIMP and TIL densities (P < 0.001). Stromal CD68+ and CD163+ macrophage densities had a significant relationship with intra-epithelial and stromal CD3+ (P = 0.001 and P < 0.001, respectively) and CD8+ (P < 0.001) T cells. High intra-epithelial CD68+ macrophage density was associated with worse overall survival (HR = 1.386, 95% CI = 1.043-1.843, P = 0.025) and progression-free survival (HR = 1.522, 95% CI = 1.146-2.020, P = 0.004). Intra-epithelial CD68+ macrophage density was also an independent prognostic factor of the progression-free survival (HR = 1.447, 95% CI = 1.076-1.947, P = 0.015) of CRC patients regardless of pTNM stage, lymphatic, venous, and perineural invasions and TIL densities. CONCLUSION: Our results indicate that the density of intratumoural macrophages is a useful prognostic indicator for further stratifying T cell populations in CRC.

Subsets of microsatellite-unstable colorectal cancers exhibit discordance between the CpG island methylator phenotype and MLH1 methylation status.

Although the presence of MLH1 methylation in microsatellite-unstable colorectal cancer generally indicates involvement of the CpG island methylator phenotype (CIMP) in the development of the tumor, these two conditions do not always correlate. A minority of microsatellite-unstable colorectal cancers exhibit discordance between CIMP and MLH1 methylation statuses. However, the clinicopathological features of such microsatellite-unstable colorectal cancers with discrepant MLH1 methylation and CIMP statuses remain poorly studied. Microsatellite-unstable colorectal cancers (n=220) were analyzed for CIMP and MLH1 methylation statuses using the MethyLight assay. Based on the combinatorial CIMP and MLH1 methylation statuses, the microsatellite-unstable colorectal cancers were grouped into four subtypes (CIMP-high (CIMP-H) MLH1 methylation-positive (MLH1m+), CIMP-H MLH1 methylation-negative, CIMP-low/0 (CIMP-L/0) MLH1m+, and CIMP-L/0 MLH1 methylation-negative), which were compared in terms of their associations with clinicopathological and molecular features. The CIMP-L/0 MLH1 methylation-negative and CIMP-H MLH1m+ subtypes were predominant, comprising 63.6 and 24.1% of total microsatellite-unstable colorectal cancers, respectively. The discordant subtypes, CIMP-H MLH1 methylation-negative and CIMP-L/0 MLH1m+, were found in 5 and 7% of microsatellite-unstable colorectal cancers, respectively. The CIMP-H MLH1 methylation-negative subtype exhibited elevated incidence rates in male patients and was associated with larger tumor size, more frequent loss of MSH2 expression, increased frequency of KRAS mutation, and advanced cancer stage. The CIMP-L/0 MLH1m+ subtype was associated with onset at an earlier age, a predominance of MLH1 loss, and earlier cancer stage. None of the CIMP-L/0 MLH1m+ subtype patients succumbed to death during the follow-up. Our findings suggest that the discordant subtypes of colorectal cancers exhibit distinct clinicopathological and molecular features, although the proportion of discordant subtypes is low. The microsatellite-unstable colorectal cancers of the same CIMP status tended to exhibit different clinicopathological features depending on MLH1 methylation status.

Clinicopathologic and molecular characteristics of synchronous colorectal cancers: heterogeneity of clinical outcome depending on microsatellite instability status of individual tumors.

BACKGROUND: The contribution of chromosomal instability, microsatellite instability, and epigenetic instability to the development of synchronous colorectal carcinomas is controversial. OBJECTIVE: This study aimed to investigate the relative roles of microsatellite instability and epigenetic instability in the development of synchronous colorectal cancers. DESIGN: This was a retrospective study of medical records with histologic, immunohistochemical, and molecular examination of stored tissue samples. SETTING: The study took place at Seoul National University Hospital, Korea. PATIENTS: A total of 46 patients with synchronous colorectal cancers and 105 patients with solitary colorectal cancers were included. MAIN OUTCOME MEASURES: Clinicopathologic and molecular characteristics including microsatellite instability, mismatch repair gene expression, CpG island methylator phenotype, and mutation of KRAS and BRAF were analyzed. RESULTS: Patients with synchronous tumors were more likely to be men than those with solitary tumors and had a tendency toward colocalization of individual tumors in the left or right colon. MSI-deficient cancers were more frequent in synchronous than in solitary cancers. The frequencies of CpG island methylator phenotype-high and KRAS and BRAF mutations were not different between synchronous and solitary cancers. No differences between synchronous cancers and solitary cancers were observed in overall survival or progression-free survival. Within the synchronous cancer group, patients with individual tumors discordant for microsatellite instability status had the worst clinical outcome, whereas those with individual tumors concordant for microsatellite instability-deficient status had the best clinical outcome. LIMITATIONS: The study was limited by its retrospective nature. Molecular analysis was performed only on cancerous lesions. CONCLUSIONS: Our findings suggest that microsatellite instability plays a more important role than does epigenetic instability in the development of synchronous colorectal cancers, and that information regarding concordant or discordant microsatellite instability status between individual tumors might help to predict clinical outcome of synchronous colorectal cancers.