Tumor infiltrating lymphocytes: an intriguing player in the survival of colorectal cancer patients

[Predictive value of intraepithelial (CD3) T-lymphocyte infiltration in resected colorectal cancer]

INTRODUCTION

Colorectal cancer (CRC) can induce an anti-tumoral immune response mediated by T-lymphocytes, which express CD3.

OBJECTIVES

To analyze the prognostic value of tissue expression of intraepithelial CD3 (CD3I) both overall and in the early tumoral stages.

METHODS

We revised 251 patients with resected CRC and favorable clinical course. CD3I expression was analyzed by immunohistochemistry. Multivariate analysis was used to analyze the variables independently associated with survival. We analyzed CD3I(+) expression in relation to survival and tumoral progression, both overall and in patients with pTNM(I-II) stage tumors. The sensitivity, specificity, positive and negative predictive values and diagnostic accuracy of CD3I expression were analyzed.

RESULTS

A total of 25.9% of patients with CRC were CD3I(+). After a mean follow-up of 74 months, CD3I(+) expression showed a favorable prognostic value for survival in the multivariate analysis (p=0.045). Survival curves and absence of tumoral progression were more favorable in CD3I(+) cases, both overall (p=0.009 and p=0.004, respectively), and in stages I-II (p=0.029 and p=0.015). The specificity and positive predictive value of CD3I(+) were as follows: Survival: overall: specificity =0.89; positive predictive value =0.91. Stage (I-II): specificity =0.94; positive predictive value =0.98. Absence of tumoral progression: overall: specificity=0.89; positive predictive value =0.88. Stage (I-II): specificity =0.92; positive predictive value =0.96.

CONCLUSIONS

CD3I expression has an favorable independent prognostic value, with statistically significantly higher percentages of survival and absence of tumoral progression. This more favorable outcome is maintained in the less advanced stages (I-II). CD3I expression shows high specificity and positive predictive value.

Prognostic impact of β-2-microglobulin expression in colorectal cancers stratified by mismatch repair status

Background

β-2-microglobulin (B2M) is essential for antigen presentation, yet may also possess proto-oncogenic properties.

Aim

To determine the prognostic impact of B2M in patients with mismatch repair (MMR) proficient and deficient colorectal cancer (CRC) and to investigate whether this effect on outcome is dependent on the local immune response.

Methods

B2M protein expression and tumour-infiltrating immune cells (CD3, CD16, CD163, CD20, CD4, CD45RO, CD56, CD68, CD8, FoxP3, GranzymeB, iNOS, mast cell tryptase, MUM1, PD1, TIA-1) were evaluated in a well characterised tissue microarray of 408 CRCs. The predictive value for clinicopathological features and the prognostic significance of B2M expression were analysed, stratified by MMR status and the immunohistological characteristics of immune cell infiltrates.

Results

Interobserver agreement for B2M staining was high (intra-class correlation coefficient=0.91). Complete B2M loss was more frequent in MMR-deficient (19.4%) compared to MMR-proficient (7.1%) tumours (p<0.001). In MMR-deficient cases, B2M loss predicted rare local recurrence (p=0.034), infrequent nodal-positivity (p=0.035), absence of distant metastasis (p=0.048; sensitivity=100%) and a trend towards favourable survival (p=0.124) independent of immune infiltrates. No associations between B2M and clinicopathological features were observed in MMR-proficient cases.

Conclusions

Our data show for the first time that absence of B2M protein expression identifies MMR-deficient cancers with a favourable clinical course and absence of metastatic disease. Validation of B2M protein expression for sub-classification of MMR-deficient CRC is recommended for future clinical trials.

A multi-factorial genetic model for prognostic assessment of high risk melanoma patients receiving adjuvant interferon

Purpose

IFNa was the first cytokine to demonstrate anti-tumor activity in advanced melanoma. Despite the ability of high-dose IFNa reducing relapse and mortality by up to 33%, large majority of patients experience side effects and toxicity which outweigh the benefits. The current study attempts to identify genetic markers likely to be associated with benefit from IFN-a2b treatment and predictive for survival.

Experimental design

We tested the association of variants in FOXP3 microsatellites, CTLA4 SNPs and HLA genotype in 284 melanoma patients and their association with prognosis and survival of melanoma patients who received IFNa adjuvant therapy.

Results

Univariate survival analysis suggested that patients bearing either the DRB1*15 or HLA-Cw7 allele suffered worse OS while patients bearing either HLA-Cw6 or HLA-B44 enjoyed better OS. DRB1*15 positive patients suffered also worse RFS and conversely HLA-Cw6 positive patients had better RFS. Multivariate analysis revealed that a five-marker genotyping signature was prognostic of OS independent of disease stage. In the multivariate Cox regression model, HLA-B38 (p = 0.021), HLA-C15 (p = 0.025), HLA-C3 (p = 0.014), DRB1*15 (p = 0.005) and CT60*G/G (0.081) were significantly associated with OS with risk ratio of 0.097 (95% CI, 0.013–0.709), 0.387 (95% CI, 0.169–0.889), 0.449 (95% CI, 0.237–0.851), 1.948 (95% CI, 1.221–3.109) and 1.484 (95% IC, 0.953–2.312) respectively.

Conclusion

These results suggest that gene polymorphisms relevant to a biological occurrence are more likely to be informative when studied in concert to address potential redundant or conflicting functions that may limit each gene individual contribution. The five markers identified here exemplify this concept though prospective validation in independent cohorts is needed.

An improved image analysis method for cell counting lends credibility to the prognostic significance of T cells in colorectal cancer

Numerous immunohistochemically detectable proteins, such as immune cell surface (CD) proteins, vascular endothelial growth factor, and matrix metalloproteinases, have been proposed as potential prognostic markers in colorectal cancer (CRC) and other malignancies. However, the lack of reproducibility has been a major problem in validating the clinical use of such markers, and this has been attributed to insufficiently robust methods used in immunohistochemical staining or its assessment. In this study, we assessed how computer-assisted image analysis might contribute to the reliable assessment of positive area percentage and immune cell density in CRC specimens, and subsequently, we applied the computer-assisted cell counting method in assessing the prognostic value of T cell infiltration in CRC. The computer-assisted analysis methods were based on separating hematoxylin and diaminobenzidine color layers and then applying a brightness threshold using open source image analysis software ImageJ. We found that computer-based analysis results in a more reproducible assessment of the immune positive area percentage than visual semiquantitative estimation. Computer-assisted immune cell counting was rapid to perform and accurate (Pearson r > 0.96 with exact manual cell counts). Moreover, the computer-assisted determination of peritumoral and stromal T cell density had independent prognostic value. Our results suggest that computer-assisted image analysis, utilizing freely available image analysis software, provides a valuable alternative to semiquantitative assessment of immunohistochemical results in cancer research, as well as in clinical practice. The advantages of using computer-assisted analysis include objectivity, accuracy, reproducibility, and time efficiency. This study supports the prognostic value of assessing T cell infiltration in CRC.

Immune microenvironmental shift along human colorectal adenoma-carcinoma sequence: is it relevant to tumor development, biomarkers and biotherapeutic targets?

Human colorectal carcinoma (CRC) is one of the leading cancers. Every year, the WHO estimates a total of 945,000 new CRC cases, with 492,000 deaths worldwide. Most CRCs arise from the main premalignant lesion, colorectal adenomas, and the progression of colorectal adenoma to CRCs may take a long-term time course. The development of human CRCs is not only determined by the adenomatous cells, but also by the interaction between adenomatous cells and host immune environment. In response to tumor initiation or invasion, many inflammatory cells and components will be inevitably activated and form an inflammatory microenvironment surrounding the CRC tumors. Accumulative evidence has revealed that inflammatory response plays a key role in the development of human CRCs by implicating in many aspects including in determining the microenvironmental immune function shift from immunosurveillance to immunosuppression and significantly influences the progression of precancerous lesions to cancers. In this review, the functional changes of immune microenvironment from precancerous stage (adenoma) to cancer stage are summarized, and their potential as predictive biomarkers and biotherapeutic significance in preventing the development of CRCs are discussed.

Immunotherapy for metastatic colorectal cancer: present status and new options

Although no immunotherapeutic treatment is approved for colorectal cancer (CRC) patients, promising results from clinical trials suggest that several immunotherapeutic strategies may prove efficacious and applicable to this group of patients. This review describes the immunogenicity of CRC and presents the most interesting strategies investigated so far: cancer vaccination including antigen-defined vaccination and dendritic cell vaccination, chemo-immunotherapy, and adoptive cell transfer. Future treatment options as well as the possibility of combining existing therapies will be discussed along with the challenges presented by tumor escape mechanisms.

Ex-vivo clonally expanded B lymphocytes infiltrating colorectal carcinoma are of mature immunophenotype and produce functional IgG

Background

Tumor infiltrating B cells (TiBc) have not yet been investigated in detail. This may at least in part be due to technical difficulties. Here we describe a straightforward and reproducible method to isolate and culture TiBc from primary colorectal carcinomas (CRC).

Methods/Results

TiBc cultures were generated by Epstein-Barr virus (EBV) immortalization. With this method, monoclonal TiBc cultures were obtained for 14/19 CRCs. As assessed by flow cytometry and ELISA, TiBc showed an activated immunophenotype (CD23⁺, CD80⁺) and produced immunoglobulin (Ig; IgG secretion in 55% of the cultures). In functional in vitro analysis, most of the IgGs specifically bound to allogeneic CRC target cells. These data suggest that TiBc are antigen-experienced and thus may exhibit functionality in situ. Additionally, mini-cultures generated from 12 further CRCs revealed TiBc outgrowth exclusively in the presence of EBV.

Conclusion

In summary, this simple method provides a cellular tool and our data set the stage for analysing the bivalent role of TiBc; being antigen-presenting cells on the one hand and tumor-specific antibody producers on the other. Additionally, the generation of long-term TiBc cultures and their monoclonal Ig may serve to identify novel tumor-specific antigens.

Acute sensitization of colon cancer cells to inflammatory cytokines by prophase arrest

Understanding how colon cancer cells survive within the inflammatory milieu of a tumor, and developing approaches that increase their sensitivity to inflammatory cytokines, may ultimately lead to novel approaches for colon cancer therapy and prevention. Analysis of a number of chemopreventive and therapeutic agents reveal that HDAC inhibitors are particularly adept at sensitizing colon cancer cells TNF or TRAIL mediated apoptosis. In vivo data are consistent with an interaction between SAHA and TNF in inducing apoptosis, as AOM-induced colon tumors express elevated levels of TNF and are more sensitive to SAHA administration. Cell cycle analysis and time-lapse imaging indicated a close correspondence between SAHA-induced prophase arrest and TNF or TRAIL-induced apoptosis. Prophase arrest induced by the Aurora kinase inhibitor VX680 likewise sensitized cells to TNF and TRAIL, with siRNA analysis pointing to Aurora kinase A (and not Aurora kinase B) as being the relevant target for this sensitization. We propose that agents that promote prophase arrest may help sensitize cancer cells to TNF and other inflammatory cytokines. We also discuss how circumvention of an early mitotic checkpoint may facilitate cancer cell survival in the inflammatory micro-environment of the tumor.

Microsatellite instability, EMAST, and morphology associations with T cell infiltration in colorectal neoplasia

BACKGROUND AND OBJECTIVES

Colorectal tumors are often observed with tumor infiltrating lymphocytes, presumably as a host-immune response, and patterns may segregate by types of genomic instability. Microsatellite unstable (MSI) colorectal cancers contain a pronounced lymphocyte reaction that can pathologically identify these tumors. Colorectal tumors with elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) have not been examined for lymphocyte patterns.

METHODS

We evaluated a 108-person cohort with 24 adenomas and 84 colorectal cancers for MSI and EMAST. Immunohistochemical detection of CD4+ and CD8+ T cell infiltration were performed. Prognostic relevance was assessed by survival analysis.

RESULTS

CD8+ T cell infiltration in the tumor cell nest (p = 0.013) and tumor stroma (p = 0.004) were more prominent in moderately and poorly differentiated adenocarcinoma than in adenoma and well-differentiated adenocarcinoma. CD8+ T cells in the tumor cell nest (p = 0.002) and tumor stroma (p = 0.009) were at higher density in tumors with ulcerating features compared to tumors with a sessile or polypoid appearance. MSI-H tumors showed a higher density of CD8+ T cell infiltrations in tumor cell nests (p = 0.003) and tumor stroma (p = 0.001). EMAST-positive tumors showed a higher density of CD8+ T cell infiltrations than EMAST-negative tumors both in tumor cell nest (p = 0.027) and in tumor stroma (p = 0.003). These changes were not observed with CD4+ T lymphocytes. There was no difference in cancer patient survival based on density of CD8+ cells.

CONCLUSIONS

CD8+ T lymphocytes, but not CD4+ cells, were increased in tumor cell nests and the tumor stroma in both MSI and EMAST tumors, and showed higher infiltration in ulcerated tumors. CD8+ T lymphocyte infiltration is associated with both EMAST and MSI patterns, and increases with histological advancement.

Clinical effects of adjuvant active specific immunotherapy differ between patients with microsatellite-stable and microsatellite-instable colon cancer

PURPOSE

Active specific immunotherapy (ASI) consisting of an autologous tumor cell vaccine given as adjuvant treatment has been shown to improve recurrence-free survival of patients with colon cancer. The aim of the current retrospective study was to investigate whether the beneficial effects of ASI given as adjuvant treatment correlated with microsatellite instability (MSI), which is considered an important biologic determinant of colon cancer.

EXPERIMENTAL DESIGN

Microsatellite status was assessed on archival tumor material from patients with stage II and III colon cancer. Microsatellite status was next associated with clinical outcome in control and ASI treatment groups using Kaplan-Meier analysis.

RESULTS

We identified 162 (83%) microsatellite-stable tumors (MSS) and 34 (17%) MSI tumors. Patients with MSI tumors did well in recurrence-free interval (RFI) as well as disease-specific survival (DSS) irrespective of treatment arm and tumor stage. Patients with MSI tumors had significantly fewer recurrences and prolonged DSS than those with MSS tumors. Patients with MSS Dukes B tumors who received ASI treatment showed a significantly improved recurrence-free survival compared with controls. ASI treatment did not improve recurrence-free interval or DSS for patients with MSS Dukes C tumors.

CONCLUSION

This retrospective study indicated that patients with MSI tumors did well, irrespective of treatment arm and tumor stage. The data also indicate that the clinical benefit, measured as recurrence-free survival, from adjuvant ASI treatment of patients with colon cancer was restricted to patients with MSS Dukes B tumors.

Tumor evasion from T cell surveillance

An intact immune system is essential to prevent the development and progression of neoplastic cells in a process termed immune surveillance. During this process the innate and the adaptive immune systems closely cooperate and especially T cells play an important role to detect and eliminate tumor cells. Due to the mechanism of central tolerance the frequency of T cells displaying appropriate arranged tumor-peptide-specific-T-cell receptors is very low and their activation by professional antigen-presenting cells, such as dendritic cells, is frequently hampered by insufficient costimulation resulting in peripheral tolerance. In addition, inhibitory immune circuits can impair an efficient antitumoral response of reactive T cells. It also has been demonstrated that large tumor burden can promote a state of immunosuppression that in turn can facilitate neoplastic progression. Moreover, tumor cells, which mostly are genetically instable, can gain rescue mechanisms which further impair immune surveillance by T cells. Herein, we summarize the data on how tumor cells evade T-cell immune surveillance with the focus on solid tumors and describe approaches to improve anticancer capacity of T cells.

An MSI tumor specific frameshift mutation in a coding microsatellite of MSH3 encodes for HLA-A0201-restricted CD8+ cytotoxic T cell epitopes

BACKGROUND

Microsatellite instability (MSI) resulting from inactivation of the DNA mismatch repair system (MMR) characterizes a highly immunological subtype of colorectal carcinomas. Those tumors express multiple frameshift-mutated proteins which present a unique pool of tumor-specific antigens. The DNA MMR protein MSH3 is frequently mutated in MSI(+) colorectal tumors, thus making it an attractive candidate for T cell-based immunotherapies.

METHODOLOGY/PRINCIPAL FINDINGS

FSP-specific CD8(+) T cells were generated from a healthy donor using reverse immunology. Those T cells specifically recognized T2 cells sensitized with the respective peptides. Specific recognition and killing of MSI(+) colorectal carcinoma cells harbouring the mutated reading frame was observed. The results obtained with T cell bulk cultures could be reproduced with T cell clones obtained from the same cultures. Blocking experiments (using antibodies and cold target inhibition) confirmed peptide as well as HLA-A0201-specificity.

CONCLUSIONS

We identified two novel HLA-A0201-restricted cytotoxic T cell epitopes derived from a (-1) frameshift mutation of a coding A(8) tract within the MSH3 gene. These were (386)-FLLALWECSL (FSP18) and (387)-LLALWECSL (FSP19) as well as (403)-IVSRTLLLV (FSP23) and (402)-LIVSRTLLLV (FSP31), respectively. These results suggest that MSH3(-1) represents another promising MSI(+)-induced target antigen. By identifying two distinct epitopes within MSH3(-1), the sustained immunogenicity of the frameshift mutated sequence was confirmed. Our data therefore encourage further exploitation of MSH3 as a piece for peptide-based vaccines either for therapeutic or--even more important--preventive purposes.

T cells and adoptive immunotherapy: recent developments and future prospects in gastrointestinal oncology

Gastrointestinal oncology is one of the foremost causes of death: the gastric cancer accounts for 10.4% of cancer deaths worldwide, the pancreatic cancer for 6%, and finally, the colorectal cancer for 9% of all cancer-related deaths. For all these gastrointestinal cancers, surgical tumor resection remains the primary curative treatment, but the overall 5-year survival rate remains poor, ranging between 20-25%; the addition of combined modality strategies (pre- or postoperative chemoradiotherapy or perioperative chemotherapy) results in 5-year survival rates of only 30-35%. Therefore, many investigators believe that the potential for making significant progress lies on understanding and exploiting the molecular biology of gastrointestinal tumors to investigate new therapeutic strategies such as specific immunotherapy. In this paper we will focus on recent knowledge concerning the role of T cells and the use of T adoptive immunotherapy in the treatment of gastrointestinal cancers.

The role of the in situ local inflammatory response in predicting recurrence and survival in patients with primary operable colorectal cancer

Colorectal cancer progression and survival is dependent on complex interactions between the tumour and the host. The pronounced local inflammatory response in and around the tumour is thought to represent the in situ host anti-tumour immune response. Since early reports, 40 years ago, there has been a continuing interest in establishing the cellular composition of immune cell infiltrates and their relationship with survival in colorectal cancer. In this review, we comprehensively examine the evidence for the local inflammatory cell reaction/in situ immune response in predicting outcome in primary operable colorectal cancer and make recommendations as to how such information may be incorporated into routine clinical assessment. Generally, an increasing number/density of immune cells in and around the tumour is associated with improved outcome in over 100 studies. Whilst the prognostic value of a generalized lymphocytic infiltrate or non-specific peritumoural inflammatory response is strongly related to survival based on 40 different studies, it is also apparent that most individual immune cell types relate to recurrence and cancer specific survival. The evidence is particularly robust for tumour infiltrating T lymphocytes and their subsets (CD3+, CD8+, CD45RO+, FOXP3+) in addition to tumour associated macrophages, dendritic cells and neutrophils. Taken together, the evidence suggests both adaptive and innate anti-tumour immune responses play key roles in determining cancer progression. In order to establish routine clinical utility there is a need to rationalise this prognostic information, published over a 40 years period, into a standardized assessment of tumour inflammatory cell infiltrate. Such standardization may also guide development of novel therapeutic interventions.

Cancer immunology--analysis of host and tumor factors for personalized medicine

Immune cells in the tumor microenvironment have an important role in regulating tumor progression. Therefore, stimulating immune reactions to tumors can be an attractive therapeutic and prevention strategy. Cancer cells and host cells constantly interact with each other in the tumor microenvironment; thus, cancer immunology is an interdisciplinary area where integrated analysis of both host and tumor factors is needed. Cancer represents a heterogeneous group of diseases with different genetic and epigenetic alterations; therefore, molecular classification of cancer (for example lung, prostate and breast cancers) is an important component in clinical decision making. However, most studies on antitumor immunity and clinical outcome lack analysis of tumor molecular biomarkers. In this Review, we discuss colorectal cancer as a prototypical example of cancer. Common molecular classifiers of colon cancer include KRAS, BRAF and PIK3CA mutations, microsatellite instability, LINE-1 methylation, and CpG island methylator phenotype. Since tumor molecular features and immune reactions are inter-related, a comprehensive assessment of these factors is critical. Examining the effects of tumor-host interactions on clinical outcome and prognosis represents an evolving interdisciplinary field of molecular pathological epidemiology. Pathological immunity evaluation may provide information on prognosis and help identify patients who are more likely to benefit from immunotherapy.

Review of histopathological and molecular prognostic features in colorectal cancer

Prediction of prognosis in colorectal cancer is vital for the choice of therapeutic options. Histopathological factors remain paramount in this respect. Factors such as tumor size, histological type and subtype, presence of signet ring morphology and the degree of differentiation as well as the presence of lymphovascular invasion and lymph node involvement are well known factors that influence outcome. Our understanding of these factors has improved in the past few years with factors such as tumor budding, lymphocytic infiltration being recognized as important. Likewise the prognostic significance of resection margins, particularly circumferential margins has been appreciated in the last two decades. A number of molecular and genetic markers such as KRAS, BRAF and microsatellite instability are also important and correlate with histological features in some patients. This review summarizes our current understanding of the main histopathological factors that affect prognosis of colorectal cancer.

The prognostic influence of tumour-infiltrating lymphocytes in cancer: a systematic review with meta-analysis

Background:

Tumour-infiltrating lymphocytes (TILs) are often found in tumours, presumably reflecting an immune response against the tumour. We carried out a systematic review and meta-analysis, aiming to establish pooled estimates for survival outcomes based on the presence of TILs in cancer.

Methods:

A Pubmed and Embase literature search was designed. Studies were included, in which the prognostic significance of intratumoural CD3+, CD4+, CD8+, and FoxP3+ lymphocytes, as well as ratios between these subsets, were determined in solid tumours.

Results:

In pooled analysis, CD3+ TILs had a positive effect on survival with a hazard ratio (HR) of 0.58 (95% confidence interval (CI) 0.43–0.78) for death, as did CD8+ TILs with a HR of 0.71 (95% CI 0.62–0.82). FoxP3+ regulatory TILs were not linked to overall survival, with a HR of 1.19 (95% CI 0.84–1.67). The CD8/FoxP3 ratio produced a more impressive HR (risk of death: HR 0.48, 95% CI 0.34–0.68), but was used in relatively few studies. Sample size and follow-up time seemed to influence study outcomes.

Conclusion:

Any future studies should be carefully designed, to prevent overestimating the effect of TILs on prognosis. In this context, ratios between TIL subsets may be more informative.

Immune Cells in Colorectal Cancer: Prognostic Relevance and Role of MSI

There is growing evidence that both local and systemic inflammatory responses play an important role in the progression of a variety of solid tumors. Colorectal cancer (CRC) results from the cumulative effect of sequential genetic alterations, leading to the expression of tumor-associated antigens possibly inducing a cellular anti-tumor immune response. It is well recognized that cytotoxic lymphocytes (CTLs) constitute one of the most important effector mechanisms of anti-tumor-immunity. However, their potential prognostic influence in CRC remains controversial. In addition, other key players like natural killer cells, tumor associated macrophages and regulatory T cells play an important role in the immune attack against CRC and need further investigation. This review will mainly focus on the role of the adaptive immune system in CRC and particularly in regard to microsatellite instability.

Crosstalk between medulloblastoma cells and endothelium triggers a strong chemotactic signal recruiting T lymphocytes to the tumor microenvironment

Cancer cells can live and grow if they succeed in creating a favorable niche that often includes elements from the immune system. While T lymphocytes play an important role in the host response to tumor growth, the mechanism of their trafficking to the tumor remains poorly understood. We show here that T lymphocytes consistently infiltrate the primary brain cancer, medulloblastoma. We demonstrate, both in vitro and in vivo, that these T lymphocytes are attracted to tumor deposits only after the tumor cells have interacted with tumor vascular endothelium. Macrophage Migration Inhibitory Factor (MIF)" is the key chemokine molecule secreted by tumor cells which induces the tumor vascular endothelial cells to secrete the potent T lymphocyte attractant "Regulated upon Activation, Normal T-cell Expressed, and Secreted (RANTES)." This in turn creates a chemotactic gradient for RANTES-receptor bearing T lymphocytes. Manipulation of this pathway could have important therapeutic implications.

Colorectal cancer prognosis depends on T-cell infiltration and molecular characteristics of the tumor

The aim of this study was to relate the density of tumor infiltrating T cells to cancer-specific survival in colorectal cancer, taking into consideration the CpG island methylator phenotype (CIMP) and microsatellite instability (MSI) screening status. The T-cell marker CD3 was stained by immunohistochemistry in 484 archival tumor tissue samples. T-cell density was semiquantitatively estimated and scored 1-4 in the tumor front and center (T cells in stroma), and intraepithelially (T cells infiltrating tumor cell nests). Total CD3 score was calculated as the sum of the three CD3 scores (range 3-12). MSI screening status was assessed by immunohistochemistry. CIMP status was determined by quantitative real-time PCR (MethyLight) using an eight-gene panel. We found that patients whose tumors were highly infiltrated by T cells (total CD3 score ≥7) had longer survival compared with patients with poorly infiltrated tumors (total CD3 score ≤4). This finding was statistically significant in multivariate analyses (multivariate hazard ratio, 0.57; 95% confidence interval, 0.31-1.00). Importantly, the finding was consistent in rectal cancer patients treated with preoperative radiotherapy. Although microsatellite unstable tumor patients are generally considered to have better prognosis, we found no difference in survival between microsatellite unstable and microsatellite stable (MSS) colorectal cancer patients with similar total CD3 scores. Patients with MSS tumors highly infiltrated by T cells had better prognosis compared with intermediately or poorly infiltrated microsatellite unstable tumors (log rank P=0.013). Regarding CIMP status, CIMP-low was associated with particularly poor prognosis in patients with poorly infiltrated tumors (multivariate hazard ratio for CIMP-low versus CIMP-negative, 3.07; 95% confidence interval, 1.53-6.15). However, some subset analyses suffered from low power and are in need of confirmation by independent studies. In conclusion, patients whose tumors are highly infiltrated by T cells have a beneficial prognosis, regardless of MSI, whereas the role of CIMP status in this context is less clear.

Prognostic value of colorectal cancer biomarkers

Despite the large amount of data in cancer biology and many studies into the likely survival of colorectal cancer (CRC) patients, knowledge regarding the issue of CRC prognostic biomarkers remains poor. The Tumor-Node-Metastasis (TNM) staging system continues to be the most powerful and reliable predictor of the clinical outcome of CRC patients. The exponential increase of knowledge in the field of molecular genetics has lead to the identification of specific alterations involved in the malignant progression. Many of these genetic alterations were proposed as biomarkers which could be used in clinical practice to estimate CRC prognosis. Recently there has been an explosive increase in the number of putative biomarkers able to predict the response to specific adjuvant treatment. In this review we explore and summarize data concerning prognostic and predictive biomarkers and we attempt to shed light on recent research that could lead to the emergence of new biomarkers in CRC.

Tumour-infiltrating T-cell subsets, molecular changes in colorectal cancer, and prognosis: cohort study and literature review

The abundance of tumour-infiltrating T-cells has been associated with microsatellite instability (MSI) and a favourable prognosis in colorectal cancer. However, numerous molecular alterations have been associated with clinical outcome, and potentially confounding the biological and prognostic significance of tumour-infiltrating T-cells. We utilized a database of clinically and molecularly-annotated colon and rectal carcinoma cases (N = 768; stage I-IV) in two prospective cohort studies (the Nurses' Health Study and the Health Professionals Follow-up Study) and quantified the densities of CD3(+), CD8(+), CD45RO(+) (PTPRC), and FOXP3(+) cells within neoplastic epithelial areas using an Ariol image analysis system and tissue microarray. We used Cox proportional hazard models to compute the mortality hazard ratio, adjusting for clinical and molecular features including KRAS, BRAF, and PIK3CA mutations, MSI, CIMP, and LINE-1 hypomethylation. The densities of CD8(+), CD45RO(+), and FOXP3(+) cells were significantly associated with patient survival in univariate analyses (P(trend) < 0.007). In the multivariate model, tumour-infiltrating CD45RO(+)-cell density, but not CD3(+), CD8(+) or FOXP3(+)-cell density, was significantly associated with survival (p = 0.0032). In multivariate linear regression analysis, MSI-high (p < 0.0001) and high-level tumour LINE-1 methylation (p = 0.0013) were independently associated with higher CD45RO(+)-cell density. The survival benefit associated with CD45RO(+) cells was independent of MSI and LINE-1 status. In conclusion, tumour-infiltrating CD45RO(+)-cell density is a prognostic biomarker associated with longer survival of colorectal cancer patients, independent of clinical, pathological, and molecular features. In addition, MSI-high and tumour LINE-1 methylation level are independent predictors of CD45RO(+)-cell density. Our data offer a possible mechanism by which MSI confers an improved clinical outcome and support efforts to augment the host immune response in the tumour microenvironment as a strategy of targeted immunotherapy.