High macrophage infiltration has been correlated to improved survival in colorectal cancer (CRC). Tumor associated macrophages (TAMs) play complex roles in tumorigenesis since they are believed to hold both tumor preventing (M1 macrophages) and tumor promoting (M2 macrophages) activities. Here we have applied an immunohistochemical approach to determine the degree of infiltrating macrophages with a M1 or M2 phenotype in clinical specimens of CRC in relation to prognosis, both in CRC in general but also in subgroups of CRC defined by microsatellite instability (MSI) screening status and the CpG island methylator phenotype (CIMP). A total of 485 consecutive CRC specimens were stained for nitric oxide synthase 2 (NOS2) (also denoted iNOS) as a marker for the M1 macrophage phenotype and the scavenger receptor CD163 as a marker for the M2 macrophage phenotype. The average infiltration of NOS2 and CD163 expressing macrophages along the invasive tumor front was semi-quantitatively evaluated using a four-graded scale. Two subtypes of macrophages, displaying M1 (NOS2⁺) or M2 (CD163⁺) phenotypes, were recognized. We observed a significant correlation between the amount of NOS2⁺ and CD163⁺ cells (P<0.0001). A strong inverse correlation to tumor stage was found for both NOS2 (P<0.0001) and CD163 (P<0.0001) infiltration. Furthermore, patients harbouring tumors highly infiltrated by NOS2⁺ cells had a significantly better prognosis than those infiltrated by few NOS2⁺ cells, and this was found to be independent of MSI screening status and CIMP status. No significant difference was found on cancer-specific survival in groups of CRC with different NOS2/CD163 ratios. In conclusion, an increased infiltration of macrophages with a M1 phenotype at the tumor front is accompanied by a concomitant increase in macrophages with a M2 phenotype, and in a stage dependent manner correlated to a better prognosis in patients with CRC.

-An active stroma is important for cancer cell invasion and metastasis. We investigated the expression of fibroblast activation protein (FAP) in relation to patient prognosis in colorectal cancer. Colorectal cancer specimens from 449 patients were immunohistochemically stained with a FAP antibody and evaluated in the tumor center and tumor front using a semiquantitative four-level scale. FAP was expressed by fibroblasts in 85–90 % of the tumors examined. High versus no/low expression in the tumor center was associated with poor prognosis (multivariate hazard ratio, HR = 1.72; 95 % CI 1.07–2.77, p = 0.025). FAP expression in the tumor front, though more frequent than in the tumor center, was not associated with prognosis. FAP expression in the tumor center was more common in specimens with positive microsatellite instability (MSI) screening status and in patients with high CpG island methylator phenotype (CIMP) status. However, inclusion of MSI screening status and CIMP status in the multivariate analysis strengthened the risk estimates for high FAP expression in the tumor center (HR = 1.89; 95 % CI 1.13–3.14; p = 0.014), emphasizing the role of FAP as an independent prognostic factor. Stromal FAP expression is common in colorectal cancer, and we conclude that high FAP expression in the tumor center, but not the tumor front, is an independent negative prognostic factor.

Purpose: The aim of this study was to relate the CpG island methylator phenotype (CIMP; characterized by extensive promoter hypermethylation) to cancer-specific survival in colorectal cancer, taking into consideration relevant clinicopathologic factors, such as microsatellite instability (MSI) screening status and the BRAF V600E mutation. Experimental Design: Archival tumor samples from 190 patients from the Northern Sweden Health and Disease Study (NSHDS) and 414 patients from the Colorectal Cancer in Umeå Study (CRUMS), including 574 with cancer-specific survival data, were analyzed for an eight-gene CIMP panel using quantitative real-time PCR (MethyLight). MSI screening status was assessed by immunohistochemistry. Results: CIMP-low patients had a shorter cancer-specific survival compared with CIMP-negative patients (multivariate hazard ratio in NSHDS, 2.01; 95% confidence interval, 1.20-3.37; multivariate hazard ratio in CRUMS, 1.48; 95% confidence interval, 1.00-2.22). This result was similar in subgroups based on MSI screening status and was statistically significant in microsatellite stable (MSS) tumors in NSHDS. For CIMP-high patients, a shorter cancer-specific survival compared with CIMP-negative patients was observed in the MSS subgroup. Statistical significance was lost after adjusting for the BRAF mutation, but the main findings were generally unaffected. Conclusions: In this study, we found a poor prognosis in CIMP-low patients regardless of MSI screening status, and in CIMP-high patients with MSS. Although not consistently statistically significant, these results were consistent in two separate patient groups and emphasize the potential importance of CIMP and MSI status in colorectal cancer research. Clin Cancer Res; 16(6); 1845–55

Mutations in KRAS, BRAF, PIK3CA and PTEN expression have been in focus to predict the effect of epidermal growth factor receptor-blocking therapy in colorectal cancer (CRC). Here, information on these four aberrations was collected and combined to a Quadruple index and used to evaluate the prognostic role of these factors in CRC. We analysed the mutation status in KRAS, BRAF and PIK3CA and PTEN expression in two separate CRC cohorts, Northern Sweden Health Disease Study (NSHDS; n=197) and Colorectal Cancer in Umeå Study (CRUMS; n=414). A Quadruple index was created, where Quadruple index positivity specifies cases with any aberration in KRAS, BRAF, PIK3CA or PTEN expression. Quadruple index positive tumours had a worse prognosis, significant in the NSHDS but not in the CRUMS cohort (NSHDS; P=0.003 and CRUMS; P=0.230) in univariate analyses but significance was lost in multivariate analyses. When analysing each gene separately, only BRAF was of prognostic significance in the NSHDS cohort (multivariate HR 2.00, 95% CI: 1.16-3.43) and KRAS was of prognostic significance in the CRUMS cohort (multivariate HR 1.48, 95% CI: 1.02-2.16). Aberrations in PIK3CA and PTEN did not add significant prognostic information. Our results suggest that establishment of molecular subgroups based on KRAS and BRAF mutation status is important and should be considered in future prognostic studies in CRC.