Chemotherapeutic implications in microsatellite unstable colorectal cancer

Personalized treatment using predictive biomarkers in solid organ malignancies: A review

In recent years, the influence of specific biomarkers in the diagnosis and prognosis of solid organ malignancies has been increasingly prominent. The relevance of the use of predictive biomarkers, which predict cancer response to specific forms of treatment provided, is playing a more significant role than ever before, as it affects diagnosis and initiation of treatment, monitoring for efficacy and side effects of treatment, and adjustment in treatment regimen in the long term. In the current review, we explored the use of predictive biomarkers in the treatment of solid organ malignancies, including common cancers such as colorectal cancer, breast cancer, lung cancer, prostate cancer, and cancers associated with high mortalities, such as pancreatic cancer, liver cancer, kidney cancer and cancers of the central nervous system. We additionally analyzed the goals and types of personalized treatment using predictive biomarkers, and the management of various types of solid organ malignancies using predictive biomarkers and their relative efficacies so far in the clinical settings.

Predictive Biomarkers and Resistance Mechanisms of Checkpoint Inhibitors in Malignant Solid Tumors

Predictive biomarkers for immune checkpoint inhibitors (ICIs) in solid tumors such as melanoma, hepatocellular carcinoma (HCC), colorectal cancer (CRC), non-small cell lung cancer (NSCLC), endometrial carcinoma, renal cell carcinoma (RCC), or urothelial carcinoma (UC) include programmed cell death ligand 1 (PD-L1) expression, tumor mutational burden (TMB), defective deoxyribonucleic acid (DNA) mismatch repair (dMMR), microsatellite instability (MSI), and the tumor microenvironment (TME). Over the past decade, several types of ICIs, including cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors, anti-programmed cell death 1 (PD-1) antibodies, anti-programmed cell death ligand 1 (PD-L1) antibodies, and anti-lymphocyte activation gene-3 (LAG-3) antibodies have been studied and approved by the Food and Drug Administration (FDA), with ongoing research on others. Recent studies highlight the critical role of the gut microbiome in influencing a positive therapeutic response to ICIs, emphasizing the importance of modeling factors that can maintain a healthy microbiome. However, resistance mechanisms can emerge, such as increased expression of alternative immune checkpoints, T-cell immunoglobulin (Ig), mucin domain-containing protein 3 (TIM-3), LAG-3, impaired antigen presentation, and alterations in the TME. This review aims to synthesize the data regarding the interactions between microbiota and immunotherapy (IT). Understanding these mechanisms is essential for optimizing ICI therapy and developing effective combination strategies.

Genomic instabilities in hepatocellular carcinoma: biomarkers and application in immunotherapies

Hepatocellular carcinoma (HCC) is one of the deadliest cancers. For patients with advanced HCC, liver function decompensation often occurs, which leads to poor tolerance to chemotherapies and other aggressive treatments. Therefore, it remains critical to develop effective therapeutic strategies for HCC. Etiological factors for HCC are complex and multifaceted, including hepatitis virus infection, alcohol, drug abuse, chronic metabolic abnormalities, and others. Thus, HCC has been categorized as a "genomically unstable" cancer due to the typical manifestation of chromosome breakage and aneuploidy, and oxidative DNA damage. In recent years, immunotherapy has provided a new option for cancer treatments, and the degree of genomic instability positively correlates with immunotherapy efficacies. This article reviews the endogenous and exogenous causes that affect the genomic stability of liver cells; it also updates the current biomarkers and their detection methods for genomic instabilities and relevant applications in cancer immunotherapies. Including genomic instability biomarkers in consideration of cancer treatment options shall increase the patients' well-being.

Unanticipated pathological clearance in two cases of clinical T4b dMMR/MSI-h advanced colorectal cancer: the potential of immune checkpoint inhibitors despite positive positron-emission tomography results

BACKGROUND

The standard treatment for colorectal cancer consists of surgery and chemotherapy, which can be combined to improve outcomes. Immune checkpoint inhibitors (ICI) are a significant advancement in the standard treatment of metastatic, unresectable colorectal cancer with deficient mismatch repair (dMMR). However, limited data are available about the use of ICI in the neoadjuvant and conversion settings. Here, we present two cases treated with ICI.

CASE PRESENTATION

Case 1: A 75-year-old male with a large, borderline resectable rectal cancer diagnosed as cT4bN1bM0 who underwent neoadjuvant chemotherapy, followed by combination ICI consisting of ipilimumab and nivolumab. After four courses of ICI, the tumor significantly shrank, but positron emission tomography still showed a positive result and R0 resection was performed. Pathological analysis revealed no residual cancer cells. The patient has been monitored without adjuvant chemotherapy, and no recurrences have occurred after one year. Case 2: A 60-year-old male with locally advanced sigmoid colon cancer who received neoadjuvant treatment with pembrolizumab. The tumor partially shrank after three courses, and continued pembrolizumab monotherapy resulted in further tumor shrinkage which still showed positive positron emission tomography. Curative sigmoidectomy with partial resection of the ileum and bladder was performed, and the pathological outcome was pCR. There was no viable tumor in the specimen. The patient has been monitored without adjuvant chemotherapy for six months, and no recurrence has been observed.

CONCLUSIONS

The present study reports two cases, including a large, borderline resectable rectal cancer after failure of chemotherapy followed by combination treatment with nivolumab and ipilimumab and one case of sigmoid colon cancer after pembrolizumab treatment, which resulted in pathological complete response. However, it remains unknown whether ICI therapy can replace surgery or diminish the optimal extent of resection, or whether adjuvant chemotherapy is needed after surgery in the case of achieving pCR after ICI therapy. Overall, this case report suggests that ICI before colorectal surgery can be effective and potentially a 'watch-and-wait" strategy could be used for cases in which ICI is effective.

Neoadjuvant Pembrolizumab in Localized Microsatellite Instability High/Deficient Mismatch Repair Solid Tumors

PURPOSE

Pembrolizumab significantly improves clinical outcomes in advanced/metastatic microsatellite instability high (MSI-H)/deficient mismatch repair (dMMR) solid tumors but is not well studied in the neoadjuvant space.

METHODS

This is a phase II open-label, single-center trial of localized unresectable or high-risk resectable MSI-H/dMMR tumors. Treatment is pembrolizumab 200 mg once every 3 weeks for 6 months followed by surgical resection with an option to continue therapy for 1 year followed by observation. To continue on study, patients are required to have radiographic or clinical benefit. The coprimary end points are safety and pathologic complete response. Key secondary end points are response rate and organ-sparing at one year for patients who declined surgery. Exploratory analyses include interrogation of the tumor immune microenvironment using imaging mass cytometry.

RESULTS

A total of 35 patients were enrolled, including 27 patients with colorectal cancer and eight patients with noncolorectal cancer. Among 33 evaluable patients, best overall response rate was 82%. Among 17 (49%) patients who underwent surgery, the pathologic complete response rate was 65%. Ten patients elected to receive one year of pembrolizumab followed by surveillance without surgical resection (median follow-up of 23 weeks [range, 0-54 weeks]). An additional eight did not undergo surgical resection and received less than 1 year of pembrolizumab. During the study course of the trial and subsequent follow-up, progression events were seen in six patients (four of whom underwent salvage surgery). There were no new safety signals. Spatial immune profiling with imaging mass cytometry noted a significantly closer proximity between granulocytic cells and cytotoxic T cells in patients with progressive events compared with those without progression.

CONCLUSION

Neoadjuvant pembrolizumab in dMMR/MSI-H cancers is safe and resulted in high rates of pathologic, radiographic, and endoscopic response, which has implications for organ-sparing strategies.

Microsatellite Instability with BRAF V600E Associated with Delayed Presentation but Poor Survival in Stage III Colorectal Cancer

Colorectal cancer (CRC) has tremendous molecular and genetic heterogeneity, making it a difficult cancer to treat. Two of the key prognostic indicators of CRC include microsatellite instability (MSI) and BRAF V600E mutation. Here, we performed a retrospective survival analysis on 145 stage II and III CRC patients treated at the University of Kansas Cancer Center between 2009 and 2020. Of the 145 patients, BRAF V600E was observed in 15% patients and MSI in 28% patients. Median survival was not reached for stage II. For stage III, patients with BRAF V600E showed poor overall survival, which worsened with concurrent presence of MSI [χ2=6.4, p=0.01]. Eighty-five percent of this group was found to have right-sided CRC. For stage III, overall survival (OS) was 27 months, 37 months, 87 months and not reached for MSI-H/BRAF V600E, MSS/BRAF V600E, MSS/BRAF WT and MSI-H/BRAF WT, respectively. Although associated with poor prognosis, presence of MSI in BRAF V600E patients was associated with delayed disease presentation (mean age 77) compared to those with stable microsatellite (mean age 63) [p=0.01]. Although median survival between the groups could not be assessed for stage II due to very few deaths and/or inadequate length of study, comparison of survival trend suggests that BRAF V600E, rather than MSI, is what drives prognosis in stage II CRC. Our findings suggest that prognostic value of MSI is more relevant for stage III than stage II CRC. Patients with MSI-H and BRAF V600E have advantage of late presentation, although at the cost of poor overall prognosis.

The Anti-Tumor Effect of the Newly Developed LAT1 Inhibitor JPH203 in Colorectal Carcinoma, According to a Comprehensive Analysis

A novel large neutral amino acid transporter 1 (LAT1)-specific inhibitor, JPH203, is expected to cause cancer-specific starvation and possess anti-tumor effects; however, its anti-tumor mechanism for colorectal cancer (CRC) remains unclear. We analyzed LAT family gene expressions in public databases using UCSC Xena and evaluated LAT1 protein expression using immunohistochemistry in 154 cases of surgically resected CRC. We also evaluated mRNA expression using polymerase chain reaction in 10 CRC cell lines. Furthermore, JPH203 treatment experiments were conducted in vitro and in vivo using an allogeneic immune-responsive mouse model with abundant stroma created via the orthotopic transplantation of the mouse-derived CRC cell line CT26 and mesenchymal stem cells. The treatment experiments were followed by comprehensive gene expression analyses with RNA sequencing. Database analyses and immunohistochemistry research on clinical specimens revealed that LAT1 expression was cancer-dominant, and its increase was accompanied by tumor progression. In vitro, JPH203 was effective in an LAT1 expression-dependent manner. In vivo, JPH203 treatment considerably reduced tumor size and metastasis, and RNA sequencing-based pathway analysis showed that not only tumor growth and amino acid metabolism pathways, but also stromal activation-related pathways were suppressed. The results of the RNA sequencing were validated in the clinical specimens, as well as both in vitro and in vivo. LAT1 expression in CRC plays an important role in tumor progression. JPH203 may inhibit the progression of CRC and tumor stromal activity.

IL-1β enhances cell viability and decreases 5-FU sensitivity in novel colon cancer cell lines derived from African American patients

Background

In the U.S., African Americans (AAs) present with the highest incidence and mortality rates for Colorectal Cancer (CRC). When compared to Caucasian American (CA) patients, AAs also have reduced response to the first line standard of care chemotherapeutic agent 5-Fluorouracil (5-FU). Previously, we observed differential gene expression between the two populations, suggesting that colon tumors from AA patients display a decreased antitumor immune response and an increased expression of genes encoding proteins involved in inflammatory processes, such as Interleukin-1β (IL-1β). Here, we investigate the role of IL-1β in modifying chemotherapeutic response and altering expression of proteins in novel AA and well-established CA colon cancer cell lines.

Methods

RNA sequencing analysis was performed to detect expression of genes involved in inflammation in AA and CA colon cancer cells. The effects of IL-1β on 5-FU response was evaluated by assessing cell viability (MTS assay) and apoptosis (flow cytometry analysis) following treatment with 5-FU alone or in combination with the cytokine. Further, we used an IL-1 receptor antagonist (IL-1Ra) to inhibit IL-1β-induced effects on 5-FU sensitivity and NF-kB pathway activation.

Results

AA colon cancer cell lines present significant increase in expression of genes IL1R2 (373-fold change (FC), IRAK1 (3.24 FC), IKBKB, (5.33 FC) NF-KB IA (5.95 FC), MYD88, (3.72 FC), IRAK3 (161 FC), TRAF5 (4.1 FC). A significant decrease in the response to 5-FU treatment, as well as a significant increase in phosphorylation of IκBα and secretion of IL-8, was seen following IL-1β treatment, in both AA and CA cell lines. Finally, treatment with IL-1Ra was able to reverse the effects induced by IL-1β, by increasing the cells sensitivity to 5-FU. IL-1Ra also inhibited phosphorylation of IκBα and IL-8 secretion.

Conclusions

Our results suggest a differential expression of inflammatory genes and proteins that might regulate the different response to IL-1β between AA and CA colon cancer cell lines. Our data also demonstrates that IL-1β is involved in modulating 5-FU response in both AA and CA colon cancer cell lines. Further investigation of these mechanisms might help elucidate the differences seen in incidence, mortality and response to therapy in AA colon cancer patients.

Long-term resistance to 5-fluorouracil promotes epithelial-mesenchymal transition, apoptosis evasion, autophagy, and reduced proliferation rate in colon cancer cells

The drug, 5-fluorouracil (5FU) is a standard first-line treatment for colorectal cancer (CRC) patients. However, drug resistance acquisition remains an important challenge for effective clinical outcomes. Here, we established a long-term drug-resistant CRC model and explored the cellular events underlying 5FU resistance. We showed that 5FU-treated cells (HCT-116 5FUR) using a prolonged treatment protocol were significantly more resistant than parental cells. Likewise, cell viability and IC50 values were also observed to increase in HCT-116 5FUR cells when treated with increasing doses of oxaliplatin, indicating a cross-resistance mechanism to other cytotoxic agents. Moreover, HCT-116 5FUR cells exhibited metabolic and molecular changes, as evidenced by increased thymidylate synthase levels and upregulated mRNA levels of ABCB1. HCT-116 5FUR cells were able to overcome S phase arrest and evade apoptosis, as well as activate autophagy, as indicated by increased LC3B levels. Cells treated with low and high doses displayed epithelial-mesenchymal transition (EMT) features, as observed by decreased E-cadherin and claudin-3 levels, increased vimentin protein levels, and increased SLUG, ZEB2 and TWIST1 mRNA levels. Furthermore, HCT-116 5FUR cells displayed enhanced migration and invasion capabilities. Interestingly, we found that the 5FU drug-resistance gene signature is positively associated with the mesenchymal signature in CRC samples, and that ABCB1 and ZEB2 co-expressed at high levels could predict poor outcomes in CRC patients. Overall, the 5FU long-term drug-resistance model established here induced various cellular events, and highlighted the importance of further efforts to identify promising targets involved in more than one cellular event to successfully overcome drug-resistance.

Neoadjuvant chemotherapy in patients undergoing colonic resection for locally advanced nonmetastatic colon cancer: A nationwide propensity score matched cohort study

AIM

Neoadjuvant chemotherapy (NCT) for nonmetastatic colon cancer is not routinely used, and is currently only recommended as a treatment option for a subgroup of patients with T4b colon cancers in clinical guidelines. However, NCT may cause downstaging of the tumour, increase resectability, eradicate micrometastases and thereby improve long-term outcomes for patients with nonmetastatic colon cancer. The aim of this study was to investigate the short-term postoperative outcomes in a nationwide cohort of patients with locally advanced colon cancer (LACC) receiving NCT.

METHOD

Using the Danish Colorectal Cancer Group Database, data were retrieved on patients diagnosed with LACC (defined as clinical T3 with extramural tumour invasion >5 mm or T4) and treated with resection with a curative intent between 2015 and 2019. Propensity score matching (PSM) in a 1:1 ratio was performed to compare short-term surgical and oncological outcomes in patients receiving NCT with patients operated on without receiving NCT.

RESULTS

A total of 179 LACC patients were treated with NCT and 1131 were not. After PSM, 145 patients remained in each group. We found no significant differences in any short-term postoperative outcomes between the two groups. We found significant differences in favour of NCT regarding radicality and pathological N category [86% vs. 81% R0 (P = 0.029) and 51% vs. 46% pN0 (P = 0.017), respectively].

CONCLUSION

Neoadjuvant chemotherapy for LACC does not result in worse short-term postoperative outcomes and may increase the R0 rate as well as node-negative disease. Results on long-term benefits including survival are awaited from several ongoing randomized controlled trials.

Consequences of the Hsp110DE9 mutation in tumorigenesis and the 5-fluorouracil-based chemotherapy response in Msh2-deficient mice

Heat shock proteins (HSPs) play oncogenic roles in human tumours. We reported a somatic inactivating mutation of HSP110 (HSP110DE9) in mismatch repair-deficient (dMMR) cancers displaying microsatellite instability (MSI) but did not assess its impact. We evaluated the impact of the Hsp110DE9 mutation on tumour development and the chemotherapy response in a dMMR knock-in mouse model (Hsp110DE9KIMsh2KO mice). The effect of the Hsp110DE9 mutation on tumorigenesis and survival was evaluated in Msh2KO mice that were null (Hsp110wt), heterozygous (Hsp110DE9KI/+), or homozygous (Hsp110DE9KI/KI) for the Hsp110DE9 mutation by assessing tumoral syndrome (organomegaly index, tumour staging) and survival (Kaplan-Meier curves). 5-Fluorouracil (5-FU), which is the backbone of chemotherapy regimens in gastrointestinal cancers and is commonly used in other tumour types but is not effective against dMMR cells in vivo, was administered to Hsp110DE9KI/KI, Hsp110DE9KI/+, and Hsp110wtMsh2KO mice. Hsp110, Ki67 (proliferation marker) and activated caspase-3 (apoptosis marker) expression were assessed in normal and tumour tissue samples by western blotting, immunophenotyping and cell sorting. Hsp110wt expression was drastically reduced or totally lost in tumours from Msh2KOHsp110DE9KI/+ and Msh2KOHsp110DE9KI/KI mice. The Hsp110DE9 mutation did not affect overall survival or tumoral syndrome in Msh2KOHsp110DE9KI/+ and Msh2KOHsp110DE9KI/KI mice but drastically improved the 5-FU response in all cohorts (Msh2KOHsp110DE9KI/KI: P5fu = 0.001; Msh2KOHsp110DE9KI/+: P5fu = 0.005; Msh2KOHsp110wt: P5fu = 0.335). Histopathological examination and cell sorting analyses confirmed major hypersensitization to 5-FU-induced death of both Hsp110DE9KI/KI and Hsp110DE9KI/+ dMMR cancer cells. This study highlights how dMMR tumour cells adapt to HSP110 inactivation but become hypersensitive to 5-FU, suggesting Hsp110DE9 as a predictive factor of 5-FU efficacy.

Curcumin and NCLX inhibitors share anti-tumoral mechanisms in microsatellite-instability-driven colorectal cancer

BACKGROUND AND AIMS

Recent evidences highlight a role of the mitochondria calcium homeostasis in the development of colorectal cancer (CRC). To overcome treatment resistance, we aimed to evaluate the role of the mitochondrial sodium-calcium-lithium exchanger (NCLX) and its targeting in CRC. We also identified curcumin as a new inhibitor of NCLX.

METHODS

We examined whether curcumin and pharmacological compounds induced the inhibition of NCLX-mediated mitochondrial calcium (mtCa2+) extrusion, the role of redox metabolism in this process. We evaluated their anti-tumorigenic activity in vitro and in a xenograft mouse model. We analyzed NCLX expression and associations with survival in The Cancer Genome Atlas (TCGA) dataset and in tissue microarrays from 381 patients with microsatellite instability (MSI)-driven CRC.

RESULTS

In vitro, curcumin exerted strong anti-tumoral activity through its action on NCLX with mtCa2+ and reactive oxygen species overload associated with a mitochondrial membrane depolarization, leading to reduced ATP production and apoptosis. NCLX inhibition with pharmacological and molecular approaches reproduced the effects of curcumin. NCLX inhibitors decreased CRC tumor growth in vivo. Both transcriptomic analysis of TCGA dataset and immunohistochemical analysis of tissue microarrays demonstrated that higher NCLX expression was associated with MSI status, and for the first time, NCLX expression was significantly associated with recurrence-free survival.

CONCLUSIONS

Our findings highlight a novel anti-tumoral mechanism of curcumin through its action on NCLX and mitochondria calcium overload that could benefit for therapeutic schedule of patients with MSI CRC.

Mapping the genomic diaspora of gastric cancer

Gastric cancer (GC) is a leading contributor to global cancer incidence and mortality. Pioneering genomic studies, focusing largely on primary GCs, revealed driver alterations in genes such as ERBB2, FGFR2, TP53 and ARID1A as well as multiple molecular subtypes. However, clinical efforts targeting these alterations have produced variable results, hampered by complex co-alteration patterns in molecular profiles and intra-patient genomic heterogeneity. In this Review, we highlight foundational and translational advances in dissecting the genomic cartography of GC, including non-coding variants, epigenomic aberrations and transcriptomic alterations, and describe how these alterations interplay with environmental influences, germline factors and the tumour microenvironment. Mapping of these alterations over the GC life cycle in normal gastric tissues, metaplasia, primary carcinoma and distant metastasis will improve our understanding of biological mechanisms driving GC development and promoting cancer hallmarks. On the translational front, integrative genomic approaches are identifying diverse mechanisms of GC therapy resistance and emerging preclinical targets, enabled by technologies such as single-cell sequencing and liquid biopsies. Validating these insights will require specifically designed GC cohorts, converging multi-modal genomic data with longitudinal data on therapeutic challenges and patient outcomes. Genomic findings from these studies will facilitate 'next-generation' clinical initiatives in GC precision oncology and prevention.

Global colorectal cancer burden in 2020 and projections to 2040

As the third most common malignancy and the second most deadly cancer, colorectal cancer (CRC) induces estimated 1.9 million incidence cases and 0.9 million deaths worldwide in 2020. The incidence of CRC is higher in highly developed countries, and it is increasing in middle- and low-income countries due to westernization. Moreover, a rising incidence of early-onset CRC is also emerging. The large number of CRC cases poses a growing global public health challenge. Raising awareness of CRC is important to promote healthy lifestyle choices, novel strategies for CRC management, and implementation of global screening programs, which are critical to reducing CRC morbidity and mortality in the future. CRC is a heterogeneous disease, and its subtype affiliation influences prognosis and therapeutic response. An accurate CRC subtype classification system is of great significance for basic research and clinical outcome. Here, we present the global epidemiology of CRC in 2020 and projections for 2040, review the major CRC subtypes to better understand CRC molecular basis, and summarize current risk factors, prevention, and screening strategies for CRC.

Can hypoxia-inducible factor-1α overexpression discriminate human colorectal cancers with different microsatellite instability?

Clinicopathological features of high-frequency microsatellite instability (MSI-H) colorectal cancers (CRCs) are different from low-frequency MSI (MSI-L) and microsatellite stable (MSS) CRCs. The clinical features of MSI-L cases are unknown, and although the tumors usually show instability for dinucleotide markers, evaluation based on dinucleotides alone could lead to the misclassification of MSI-L or MSS as MSI-H. In this research, we investigated the usefulness of hypoxia-inducible factor-1α (HIF-1α) expression to discriminate MSI-L from MSS and MSI-H in human CRC. Tumor tissue from 94 CRC patients was used to determine the expression level of HIF-1α mRNA and HIF-1α protein using quantitative real-time PCR and immunohistochemistry analyses, respectively. The results indicated that HIF-1α mRNA and HIF-1α protein levels were upregulated in CRC patients compared with controls (P < 0.0001). Average HIF-1α expression in tissues with advanced stages and grades was also higher than that in earlier stages and grades. Expression of HIF-1α mRNA varied between CRC patients with different types of microsatellite instability (MSS, MSI-L and MSI-H). Taken together, our findings provide preliminary evidence that HIF-1α expression level in CRC tumors correlates with different MSI categories. HIF-1α expression may therefore represent a novel marker to separate the MSI-L group from the MSS and MSI-H groups.

Predictive biomarkers for 5-fluorouracil and oxaliplatin-based chemotherapy in gastric cancers via profiling of patient-derived xenografts

Gastric cancer (GC) is commonly treated by chemotherapy using 5-fluorouracil (5-FU) derivatives and platinum combination, but predictive biomarker remains lacking. We develop patient-derived xenografts (PDXs) from 31 GC patients and treat with a combination of 5-FU and oxaliplatin, to determine biomarkers associated with responsiveness. When the PDXs are defined as either responders or non-responders according to tumor volume change after treatment, the responsiveness of PDXs is significantly consistent with the respective clinical outcomes of the patients. An integrative genomic and transcriptomic analysis of PDXs reveals that pathways associated with cell-to-cell and cell-to-extracellular matrix interactions enriched among the non-responders in both cancer cells and the tumor microenvironment (TME). We develop a 30-gene prediction model to determine the responsiveness to 5-FU and oxaliplatin-based chemotherapy and confirm the significant poor survival outcomes among cases classified as non-responder-like in three independent GC cohorts. Our study may inform clinical decision-making when designing treatment strategies.

Relationship between microsatellite status and immune microenvironment of colorectal cancer and its application to diagnosis and treatment

Due to advances in understanding the immune microenvironment of colorectal cancer (CRC), microsatellite classification (dMMR/MSI-H and pMMR/MSS) has become a key biomarker for the diagnosis and treatment of CRC patients and therefore has important clinical value. Microsatellite status is associated with a variety of clinicopathological features and affects drug resistance and the prognosis of patients. CRC patients with different microsatellite statuses have different compositions and distributions of immune cells and cytokines within their tumor microenvironments (TMEs). Therefore, there is great interest in reversing or reshaping CRC TMEs to transform immune tolerant "cold" tumors into immune sensitive "hot" tumors. This requires a thorough understanding of differences in the immune microenvironments of MSI-H and MSS type tumors. This review focuses on the relationship between CRC microsatellite status and the immune microenvironment. It focuses on how this relationship has value for clinical application in diagnosis and treatment, as well as exploring the limitations of its current application.

Challenges of Neoantigen Targeting in Lynch Syndrome and Constitutional Mismatch Repair Deficiency Syndrome

Lynch syndrome (LS) and constitutional mismatch repair deficiency (CMMRD) are hereditary disorders characterised by a highly increased risk of cancer development. This is due to germline aberrations in the mismatch repair (MMR) genes, which results in a high mutational load in tumours of these patients, including insertions and deletions in genes bearing microsatellites. This generates microsatellite instability and cause reading frameshifts in coding regions that could lead to the generation of neoantigens and opens up avenues for neoantigen targeting immune therapies prophylactically and therapeutically. However, major obstacles need to be overcome, such as the heterogeneity in tumour formation within and between LS and CMMRD patients, which results in considerable variability in the genes targeted by mutations, hence challenging the choice of suitable neoantigens. The machine-learning methods such as NetMHC and MHCflurry that predict neoantigen- human leukocyte antigen (HLA) binding affinity provide little information on other aspects of neoantigen presentation. Immune escape mechanisms that allow MMR-deficient cells to evade surveillance combined with the resistance to immune checkpoint therapy make the neoantigen targeting regimen challenging. Studies to delineate shared neoantigen profiles across patient cohorts, precise HLA binding algorithms, additional therapies to counter immune evasion and evaluation of biomarkers that predict the response of these patients to immune checkpoint therapy are warranted.

Predictive and prognostic biomarkers with therapeutic targets in colorectal cancer: A 2021 update on current development, evidence, and recommendation

Although therapeutically actionable molecular alterations are widely distributed across many cancer types, only a handful of them show evidence of clinical utility and are recommended for routine clinical practice in the management of cancers of colon and rectum (CRC). This 2021 update aims to provide a succinct summary on the use of prognostic and/or predictive biomarkers (expanded RAS, BRAF, microsatellite-high [MSI-H] or deficient mismatch repair [dMMR], neurotrophic tyrosine receptor kinase [NTRK] fusion genes, and human epidermal growth factor receptor type II [HER2] gene amplification) associated with CRC. Therapeutic implications of each relevant predictive or prognostic biomarker for patients with CRC are described, along with discussion on new developments on (1) biomarker-driven therapies such as testing of BRAF, MLH1 promoter methylation and MMR germline genes in differentiating sporadic CRC or hereditary conditions such as Lynch syndrome; (2) first-line use of immune checkpoint inhibitors in metastatic CRC; (3) risk stratification and therapy selection based on primary tumor location (left-sided vs. right-sided colon cancer); (3) atypical BRAF mutations; (4) use of EGFR directed therapy in the perioperative oligometastatic disease setting; (5) re-challenge of EGFR directed therapy and (6) personalizing therapy of fluoropyrimidine and irinotecan based on new evidence in pharmacogenomic testing. Data are collected and analyzed from available systematic reviews and meta-analyses of treatments with known therapeutic targets in CRC, which may be associated with predictive and/or prognostic biomarkers. Discussions are presented in an application-based format, with goal to empower pharmacists or other clinicians to gain awareness and understanding in biomarker-driven cancer therapy issues.

Genomic and epigenomic biomarkers in colorectal cancer: From diagnosis to therapy

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths in the United States. Despite ongoing efforts aimed at increasing screening for CRC and early detection, and development of more effective therapeutic regimens, the overall morbidity and mortality from this malignancy remains a clinical challenge. Therefore, identifying and developing genomic and epigenomic biomarkers that can improve CRC diagnosis and help predict response to current therapies are of paramount importance for improving survival outcomes in CRC patients, sparing patients from toxicity associated with current regimens, and reducing the economic burden associated with these treatments. Although efforts to develop biomarkers over the past decades have achieved some success, the recent availability of high-throughput analytical tools, together with the use of machine learning algorithms, will likely hasten the development of more robust diagnostic biomarkers and improved guidance for clinical decision-making in the coming years. In this chapter, we provide a systematic and comprehensive overview on the current status of genomic and epigenomic biomarkers in CRC, and comment on their potential clinical significance in the management of patients with this fatal malignancy, including in the context of precision medicine.

Radiogenomics in Colorectal Cancer

Simple Summary

Colorectal carcinoma is characterized by intratumoral heterogeneity that can be assessed by radiogenomics. Radiomics, high-throughput quantitative data extracted from medical imaging, combined with molecular analysis, through genomic and transcriptomic data, is expected to lead to significant advances in personalized medicine. However, a radiogenomics approach in colorectal cancer is still in its early stages and many problems remain to be solved. Here we review the progress and challenges in this field at its current stage, as well as future developments.

Abstract

The steady improvement of high-throughput technologies greatly facilitates the implementation of personalized precision medicine. Characterization of tumor heterogeneity through image-derived features—radiomics and genetic profile modifications—genomics, is a rapidly evolving field known as radiogenomics. Various radiogenomics studies have been dedicated to colorectal cancer so far, highlighting the potential of these approaches to enhance clinical decision-making. In this review, a general outline of colorectal radiogenomics literature is provided, discussing the current limitations and suggested further developments.

Treating Colorectal Cancer with Immunotherapy: Implications for Single versus Combination Therapy

PURPOSE OF REVIEW

Colorectal cancer (CRC) is the second leading cause of cancer-associated deaths in the United States, with most metastatic cases subsequently turning refractory to standard chemotherapy. One of the promising current interventions is immunotherapy that relies on harnessing the body's immune mechanisms to kill the cancer cells. The aim of this review is to highlight the implications of single versus combination immunotherapy and identify the molecular features and mutations that enhance or deter responsiveness.

RECENT FINDINGS

Based on current findings, responsiveness is associated with deficiency of mismatch repair (dMMR) genes or presence of microsatellite instability (MSI-high), with high immunoscore and tumor-mutational burden contributing to better efficacy while BRAF mutation conferring no significant effect. Combination immunotherapy demonstrates better efficacy in treating MSI-high CRC compared to single agent immunotherapy or chemotherapy.

SUMMARY

Given improved responsiveness and overall survival, there is potential for immunotherapy to change the standard of care for metastatic CRC. Furthermore, stratifying the patients by their molecular features and mutation status is critical for establishing care.

Neoadjuvant Immunotherapy-Based Systemic Treatment in MMR-Deficient or MSI-High Rectal Cancer: Case Series

Treatment options for locally advanced rectal cancer have continued to consist largely of chemotherapy, chemoradiation, and/or surgical resection. For patients who are unable to undergo these therapeutic modalities or who do not to experience a response to them, treatment options are limited. We report 3 cases of mismatch repair-deficient (dMMR) locally advanced adenocarcinoma of the rectum that showed significant response with neoadjuvant immunotherapy-based systemic treatment. The first patient was not eligible for standard therapy because of a history of radiotherapy to the prostate with concurrent comorbidities and therefore received single-agent pembrolizumab. The second patient did not respond to total neoadjuvant chemoradiation and subsequently received combined nivolumab and ipilimumab. The third patient had a known family history of Lynch syndrome and presented with locally advanced rectal cancer and a baseline carcinoembryonic antigen level of 1,566 ng/mL. She was treated using neoadjuvant pembrolizumab and FOLFOX (folinic acid, fluorouracil, oxaliplatin). In this small series, we suggest that single-agent and combined-modality neoadjuvant immunotherapy/chemotherapy appear to be safe and effective treatment options for patients with (dMMR) locally advanced rectal cancer. Our findings encourage further studies to investigate the role of neoadjuvant immunotherapy as a viable treatment strategy in this population.

Implications of Hereditary Origin on the Immune Phenotype of Mismatch Repair-Deficient Cancers: Systematic Literature Review

Microsatellite instability (MSI) represents one of the major types of genomic instability in human cancers and is most common in colorectal cancer (CRC) and endometrial cancer (EC). MSI develops as a consequence of DNA mismatch repair (MMR) deficiency, which can occur sporadically or in the context of Lynch syndrome (LS), the most common inherited tumor syndrome. MMR deficiency triggers the accumulation of high numbers of somatic mutations in the affected cells, mostly indel mutations at microsatellite sequences. MSI tumors are among the most immunogenic human tumors and are often characterized by pronounced local immune responses. However, so far, little is known about immunological differences between sporadic and hereditary MSI tumors. Therefore, a systematic literature search was conducted to comprehensively collect data on the differences in local T cell infiltration and immune evasion mechanisms between sporadic and LS-associated MSI tumors. The vast majority of collected studies were focusing on CRC and EC. Generally, more pronounced T cell infiltration and a higher frequency of B2M mutations were reported for LS-associated compared to sporadic MSI tumors. In addition, phenotypic features associated with enhanced lymphocyte recruitment were reported to be specifically associated with hereditary MSI CRCs. The quantitative and qualitative differences clearly indicate a distinct biology of sporadic and hereditary MSI tumors. Clinically, these findings underline the need for differentiating sporadic and hereditary tumors in basic science studies and clinical trials, including trials evaluating immune checkpoint blockade therapy in MSI tumors.

Personalized Medicine-Current and Emerging Predictive and Prognostic Biomarkers in Colorectal Cancer

Colorectal cancer (CRC) is the third most common cancer diagnosed worldwide and is heterogeneous both morphologically and molecularly. In an era of personalized medicine, the greatest challenge is to predict individual response to therapy and distinguish patients likely to be cured with surgical resection of tumors and systemic therapy from those resistant or non-responsive to treatment. Patients would avoid futile treatments, including clinical trial regimes and ultimately this would prevent under- and over-treatment and reduce unnecessary adverse side effects. In this review, the potential of specific biomarkers will be explored to address two key questions—1) Can the prognosis of patients that will fare well or poorly be determined beyond currently recognized prognostic indicators? and 2) Can an individual patient’s response to therapy be predicted and those who will most likely benefit from treatment/s be identified? Identifying and validating key prognostic and predictive biomarkers and an understanding of the underlying mechanisms of drug resistance and toxicity in CRC are important steps in order to personalize treatment. This review addresses recent data on biological prognostic and predictive biomarkers in CRC. In addition, patient cohorts most likely to benefit from currently available systemic treatments and/or targeted therapies are discussed in this review.

Predicting the effect of 5-fluorouracil-based adjuvant chemotherapy on colorectal cancer recurrence: A model using gene expression profiles

It is critical to identify patients with stage II and III colorectal cancer (CRC) who will benefit from adjuvant chemotherapy (ACT) after curative surgery, while the only use of clinical factors is insufficient to predict this beneficial effect. In this study, we performed genetic algorithm (GA) to select ACT candidate genes, and built a predictive model of support vector machine (SVM) using gene expression profiles from the Gene Expression Omnibus database. The model contained four ACT candidate genes (EDEM1, MVD, SEMA5B, and WWP2) and TNM stage (stage II or III). After using Subpopulation Treatment Effect Pattern Plot to determine the optimal cutoff value of predictive scores, the validated patients from The Cancer Genome Atlas database can be divided into the predictive ACT-benefit/-futile groups. Patients in the predictive ACT-benefit group with 5-fluorouracil (5-Fu)-based ACT had significantly longer relapse-free survival (RFS) compared to those without ACT (P = .015); However, the difference in RFS in the predictive ACT-futile group was insignificant (P = .596). The multivariable analysis found that the predictive groups were significantly associated with the effect of ACT (P_interaction  = .011). Consequently, we developed a predictive model based on the SVM and GA algorithm which was further validated to define patients who benefit from ACT on recurrence.

Biomarker-guided therapy for colorectal cancer: strength in complexity

The number of molecularly stratified treatment options available to patients with colorectal cancer (CRC) is increasing, with a parallel rise in the use of biomarkers to guide prognostication and treatment decision-making. The increase in both the number of biomarkers and their use has resulted in a progressively complex situation, evident both from the extensive interactions between biomarkers and from their sometimes complex associations with patient prognosis and treatment benefit. Current and emerging biomarkers also reflect the genomic complexity of CRC, and include a wide range of aberrations such as point mutations, amplifications, fusions and hypermutator phenotypes, in addition to global gene expression subtypes. In this Review, we provide an overview of current and emerging clinically relevant biomarkers and their role in the management of patients with CRC, illustrating the intricacies of biomarker interactions and the growing treatment opportunities created by the availability of comprehensive molecular profiling.

5-fluorouracil and other fluoropyrimidines in colorectal cancer: Past, present and future

5-Fluorouracil (5-FU) is an essential component of systemic chemotherapy for colorectal cancer (CRC) in the palliative and adjuvant settings. Over the past four decades, several modulation strategies including the implementation of 5-FU-based combination regimens and 5-FU pro-drugs have been developed and tested to increase the anti-tumor activity of 5-FU and to overcome the clinical resistance. Despite the encouraging progress in CRC therapy to date, the patients' response rates to therapy continue to remain low and the patients' benefit from 5-FU-based therapy is frequently compromised by the development of chemoresistance. Inter-individual differences in the treatment response in CRC patients may originate in the unique genetic and epigenetic make-up of each individual. The critical element in the current trend of personalized medicine is the proper comprehension of causes and mechanisms contributing to the low or lack of sensitivity of tumor tissue to 5-FU-based therapy. The identification and validation of predictive biomarkers for existing 5-FU-based and new targeted therapies for CRC treatment will likely improve patients' outcomes in the future. Herein we present a comprehensive review summarizing options of CRC treatment and the mechanisms of 5-FU action at the molecular level, including both anabolic and catabolic ways. The main part of this review comprises the currently known molecular mechanisms underlying the chemoresistance in CRC patients. We also focus on various 5-FU pro-drugs developed to increase the amount of circulating 5-FU and to limit toxicity. Finally, we propose future directions of personalized CRC therapy according to the latest published evidence.

Passenger mutations accurately classify human tumors

Determining the cancer type and molecular subtype has important clinical implications. The primary site is however unknown for some malignancies discovered in the metastatic stage. Moreover liquid biopsies may be used to screen for tumoral DNA, which upon detection needs to be assigned to a site-of-origin. Classifiers based on genomic features are a promising approach to prioritize the tumor anatomical site, type and subtype. We examined the predictive ability of causal (driver) somatic mutations in this task, comparing it against global patterns of non-selected (passenger) mutations, including features based on regional mutation density (RMD). In the task of distinguishing 18 cancer types, the driver mutations-mutated oncogenes or tumor suppressors, pathways and hotspots-classified 36% of the patients to the correct cancer type. In contrast, the features based on passenger mutations did so at 92% accuracy, with similar contribution from the RMD and the trinucleotide mutation spectra. The RMD and the spectra covered distinct sets of patients with predictions. In particular, introducing the RMD features into a combined classification model increased the fraction of diagnosed patients by 50 percentage points (at 20% FDR). Furthermore, RMD was able to discriminate molecular subtypes and/or anatomical site of six major cancers. The advantage of passenger mutations was upheld under high rates of false negative mutation calls and with exome sequencing, even though overall accuracy decreased. We suggest whole genome sequencing is valuable for classifying tumors because it captures global patterns emanating from mutational processes, which are informative of the underlying tumor biology.

Impact of Time to Start Systemic Therapy on the Outcomes of Patients with Metastatic Colorectal Cancer Treated with First Line FOLFOX Chemotherapy; a Patient-Level Pooled Analysis of Two Clinical Trials

BACKGROUND

Impact of time to start first-line systemic chemotherapy following diagnosis of metastatic colorectal cancer (mCRC) needs to be studied.

METHODS

This is a pooled analysis of the raw data of the comparator arms of two randomized studies (NCT00272051; NCT00305188). Univariate and multivariate analyses of predictors of overall and progression-free survival were conducted through Cox regression analysis. Factors with statistically significant P value (P < 0.05) in the univariate part of the analysis were included in the multivariate analysis.

RESULTS

In univariate analysis, time to start systemic therapy did not affect overall or progression-free survival (P=0.694; P= 0.891 respectively). In multivariate analysis for overall survival, the following factors were predictive of worse overall survival: younger age (P = 0.019), higher ECOG performance score (P = 0.001), more than one site of metastatic disease (P = 0.002), colon site of the primary tumor (P = 0.004), and no oncologic surgery to the primary tumor (P < 0.001). Likewise, in multivariate analysis for progression-free survival, the following factors were predictive of worse progression-free survival: no oncologic surgery to the primary (P < 0.001), more than one organ of metastatic disease (P < 0.001), and no concurrent bevacizumab administration (P = 0.015).

CONCLUSION

Time to start systemic chemotherapy does not appear to impact overall or progression-free survival among mCRC patients.

Impact of primary tumor side on the outcomes of patients with non-metastatic colon cancer; a patient-level pooled analysis of two clinical trials

OBJECTIVE

To assess the impact of primary tumor side on the outcomes of non-metastatic colon cancer patients included in two clinical trials.

METHODS

Overall and disease-free survivals were assessed according to the side of the tumor, through Kaplan-Meier analysis. Univariate and Multivariate analysis of predictors of disease-free survival was performed through Cox regression analysis.

RESULTS

Kaplan-Meier analysis of disease-free survival according to the side of the primary tumor was conducted. In the overall cohort, the right-sided disease has longer disease-free survival compared to left-sided disease (p = 0.005). When the analysis was repeated among different treatment strata (observation, adjuvant 5FU/LCV, adjuvant edrecolomab), right-sided colon cancer has longer disease-free survival among observation-treated patients only (p = 0.020). Multivariate analysis was conducted among the three subsets of adjuvant treatment. The left side of the primary tumor was predictive of worse disease-free survival in patients treated with observation only (p = 0.005) but not in patients treated with adjuvant 5FU/LCV (p = 0.345) or patients treated with adjuvant edrecolomab (p = 0.661).

CONCLUSION

Stage II right-sided colon cancer patients have better disease-free survival compared to stage II left-sided colon cancer patients when treated with surgery only. This survival difference disappears if patients were treated with adjuvant fluoropyrimidines.

Low-fidelity alternative DNA repair carcinogenesis theory may interpret many cancer features and anticancer strategies

We have proposed that the low-fidelity compensatory backup alternative DNA repair pathways drive multistep carcinogenesis. Here, we apply it to interpret the clinical features of cancer, such as mutator phenotype, tissue specificity, age specificity, diverse types of cancers originated from the same type of tissue, cancer susceptibility of patients with DNA repair-defective syndromes, development of cancer only for a selected number of individuals among those that share the same genetic defect, invasion and metastasis. Clinically, the theory predicts that to improve the efficacy of molecular targeted or synthetic lethal therapy, it may be crucial to inhibit the low-fidelity compensatory alternative DNA repair either directly or by blocking the signal transducers of the sustained microenvironmental stress.

Stratification of Digestive Cancers with Different Pathological Features and Survival Outcomes by MicroRNA Expression

MicroRNAs (miRNAs) are aberrantly expressed in virtually all cancer types, including digestive cancers. Herein, we aggregated and systematically analyzed miRNA expression profiles of 1765 tumor samples, including esophageal, gastric, liver, pancreatic, colon and rectal cancers, obtained through small RNA sequencing by The Cancer Genome Atlas. We found that digestive cancers of different tissue origins could be differentiated according to their miRNA expression profiles. In particular, esophageal squamous cell carcinoma and esophageal adenocarcinoma exhibited distinct miRNA expression patterns. Thirteen (e.g. miR-135b, miR-182) and sixteen (e.g. miR-139, miR-133a-1, miR-490) miRNAs were commonly upregulated and downregulated in more than four cancer types, respectively. Pertinent to pathological features, low miR-181d expression was associated with microsatellite instability in colon and gastric cancers whereas low miR-106a expression was associated with hepatitis B virus infection in hepatocellular carcinoma. Progression in colon cancer could also be predicted by low let-7f-2 and high miR-106a expression. Molecular subtypes with distinct prognostic outcomes independent of tumor-node-metastasis staging were identified in hepatocellular carcinoma and colon cancer. In total, 4 novel and 6 reported associations between specific miRNAs and patients’ survival were identified. Collectively, novel miRNA markers were identified to stratify digestive cancers with different pathological features and survival outcomes.

Genetics and Genetic Biomarkers in Sporadic Colorectal Cancer

Sporadic colorectal cancer (CRC) is a somatic genetic disease in which pathogenesis is influenced by the local colonic environment and the patient's genetic background. Consolidating the knowledge of genetic and epigenetic events that occur with initiation, progression, and metastasis of sporadic CRC has identified some biomarkers that might be utilized to predict behavior and prognosis beyond staging, and inform treatment approaches. Modern next-generation sequencing of sporadic CRCs has confirmed prior identified genetic alterations and has classified new alterations. Each patient's CRC is genetically unique, propelled by 2-8 driver gene alterations that have accumulated within the CRC since initiation. Commonly observed alterations across sporadic CRCs have allowed classification into a (1) hypermutated group that includes defective DNA mismatch repair with microsatellite instability and POLE mutations in ∼15%, containing multiple frameshifted genes and BRAF(V600E); (2) nonhypermutated group with multiple somatic copy number alterations and aneuploidy in ∼85%, containing oncogenic activation of KRAS and PIK3CA and mutation and loss of heterozygosity of tumor suppressor genes, such as APC and TP53; (3) CpG island methylator phenotype CRCs in ∼20% that overlap greatly with microsatellite instability CRCs and some nonhypermutated CRCs; and (4) elevated microsatellite alterations at selected tetranucleotide repeats in ∼60% that associates with metastatic behavior in both hypermutated and nonhypermutated groups. Components from these classifications are now used as diagnostic, prognostic, and treatment biomarkers. Additional common biomarkers may come from genome-wide association studies and microRNAs among other sources, as well as from the unique alteration profile of an individual CRC to apply a precision medicine approach to care.

Biomarker-directed Targeted Therapy in Colorectal Cancer

With advances in the understanding of the biology and genetics of colorectal cancer (CRC), diagnostic biomarkers that may predict the existence or future presence of cancer or a hereditary condition, and prognostic and treatment biomarkers that may direct the approach to therapy have been developed. Biomarkers can be ascertained and assayed from any tissue that may demonstrate the diagnostic or prognostic value, including from blood cells, epithelial cells via buccal swab, fresh or archival cancer tissue, as well as from cells shed into fecal material. For CRC, current examples of biomarkers for screening and surveillance include germline testing for suspected hereditary CRC syndromes, and stool DNA tests for screening average at-risk patients. Molecular biomarkers for CRC that may alter patient care and treatment include the presence or absence of microsatellite instability, the presence or absence of mutant KRAS, BRAF or PIK3CA, and the level of expression of 15-PGDH in the colorectal mucosa. Molecularly targeted therapies and some general therapeutic approaches rely on biomarker information. Additional novel biomarkers are on the horizon that will undoubtedly further the approach to precision or individualized medicine.

Colorectal Cancer Biomarkers: Where Are We Now?

Colorectal cancer is one of the major causes of cancer-related death in the Western world. Patient survival is highly dependent on the tumor stage at the time of diagnosis. Reduced sensitivity to chemotherapy is still a major obstacle in effective treatment of advanced disease. Due to the fact that colorectal cancer is mostly asymptomatic until it progresses to advanced stages, the implementation of screening programs aimed at early detection is essential to reduce incidence and mortality rates. Current screening and diagnostic methods range from semi-invasive procedures such as colonoscopy to noninvasive stool-based tests. The combination of the absence of symptoms, the semi-invasive nature of currently used methods, and the suboptimal accuracy of fecal blood tests results in colorectal cancer diagnosis at advanced stages in a significant number of individuals. Alterations in gene expression leading to colorectal carcinogenesis are reflected in dysregulated levels of nucleic acids and proteins, which can be used for the development of novel, minimally invasive molecular biomarkers. The purpose of this review is to discuss the commercially available colorectal cancer molecular diagnostic methods as well as to highlight some of the new candidate predictive and prognostic molecular markers for tumor, stool, and blood samples.

Efficacy of Adjuvant 5-Fluorouracil Therapy for Patients with EMAST-Positive Stage II/III Colorectal Cancer

Elevated Microsatellite Alterations at Selected Tetranucleotide repeats (EMAST) is a genetic signature found in up to 60% of colorectal cancers (CRCs) that is caused by somatic dysfunction of the DNA mismatch repair (MMR) protein hMSH3. We have previously shown in vitro that recognition of 5-fluorouracil (5-FU) within DNA and subsequent cytotoxicity was most effective when both hMutSα (hMSH2-hMSH6 heterodimer) and hMutSβ (hMSH2-hMSH3 heterodimer) MMR complexes were present, compared to hMutSα > hMutSβ alone. We tested if patients with EMAST CRCs (hMutSβ defective) had diminished response to adjuvant 5-FU chemotherapy, paralleling in vitro findings. We analyzed 230 patients with stage II/III sporadic colorectal cancers for which we had 5-FU treatment and survival data. Archival DNA was analyzed for EMAST (>2 of 5 markers mutated among UT5037, D8S321, D9S242, D20S82, D20S85 tetranucleotide loci). Kaplan-Meier survival curves were generated and multivariate analysis was used to determine contribution to risk. We identified 102 (44%) EMAST cancers. Ninety-four patients (41%) received adjuvant 5-FU chemotherapy, and median follow-up for all patients was 51 months. Patients with EMAST CRCs demonstrated improved survival with adjuvant 5FU to the same extent as patients with non-EMAST CRCs (P<0.05). We observed no difference in survival between patients with stage II/III EMAST and non-EMAST cancers (P = 0.36). There is improved survival for stage II/III CRC patients after adjuvant 5-FU-based chemotherapy regardless of EMAST status. The loss of contribution of hMSH3 for 5-FU cytotoxicity may not adversely affect patient outcome, contrasting patients whose tumors completely lack DNA MMR function (MSI-H).

The molecular pathogenesis of colorectal cancer and its potential application to colorectal cancer screening

INTRODUCTION

Advances in our understanding of the molecular genetics and epigenetics of colorectal cancer have led to novel insights into the pathogenesis of this common cancer. These advances have revealed that there are molecular subtypes of colon polyps and colon cancer and that these molecular subclasses have unique and discrete clinical and pathological features. Although the molecular characterization of these subgroups of colorectal polyps and cancer is only partially understood at this time, it does appear likely that classifying colon polyps and cancers based on their genomic instability and/or epigenomic instability status will eventually be useful for informing approaches for the prevention and early detection of colon polyps and colorectal cancer.

CONCLUSIONS

In this review, we will discuss our current understanding of the molecular pathogenesis of the polyp to cancer sequence and the potential to use this information to direct screening and prevention programs.

DNA testing and molecular screening for colon cancer

Colon cancer develops and progresses as a consequence of abnormal cellular molecular changes, many of which result in mutant DNA. Modern molecular techniques allow examination of individual patient genetic data that ascribe risk, predict outcome, and/or modify an approach to therapy. DNA testing and molecular screening are in use today and are becoming a critical and necessary part of routine patient care. Assessing at-risk patients for hereditary colon cancer is predicted to move from individual gene testing that is commonly performed today to whole exome or whole genome sequencing, providing additional vast information of the patient's genome that might not be related to the colon cancer syndrome. Detecting mutant DNA from shed tumor cells in fecal material for colon cancer screening will increase in diagnostic accuracy over time, with improvements in the panel of mutant DNA being examined and through clinical testing. DNA mutations and other molecular changes detected directly from within the colon cancer help to inform and guide the physician for the best approach for optimal patient care and outcome. The use of epidermal growth factor receptor-targeted therapy in advanced colon cancer patients requires knowledge of the mutation status for KRAS and BRAF genes, and knowing the mutational status of PIK3CA may predict how patients respond to aspirin to prevent colon cancer recurrence. Biologically driven decision-making, or precision medicine, is becoming increasingly adopted for optimal care and outcome for colon cancer patients. Gastroenterologists will need to be increasingly aware.

Molecular alterations and biomarkers in colorectal cancer

The promise of precision medicine is now a clinical reality. Advances in our understanding of the molecular genetics of colorectal cancer (CRC) are leading to the development of a variety of biomarkers that are being used as early detection markers, prognostic markers, and markers for predicting treatment responses. This is no more evident than in the recent advances in testing CRCs for specific molecular alterations in order to guide treatment with the monoclonal antibody therapies cetuximab and panitumumab, which target the epidermal growth factor receptor. In this review, we update a prior review published in 2010 and describe our current understanding of the molecular pathogenesis of CRC and how these alterations relate to emerging biomarkers for early detection and risk stratification (diagnostic markers), prognosis (prognostic markers), and the prediction of treatment responses (predictive markers).

High tumour cannabinoid CB1 receptor immunoreactivity negatively impacts disease-specific survival in stage II microsatellite stable colorectal cancer

Background

There is good evidence in the literature that the cannabinoid system is disturbed in colorectal cancer. In the present study, we have investigated whether CB₁ receptor immunoreactive intensity (CB₁IR intensity) is associated with disease severity and outcome.

Methodology/Principal Findings

CB₁IR was assessed in formalin-fixed, paraffin-embedded specimens collected with a consecutive intent during primary tumour surgical resection from a series of cases diagnosed with colorectal cancer. Tumour centre (n = 483) and invasive front (n = 486) CB₁IR was scored from 0 (absent) to 3 (intense staining) and the data was analysed as a median split i.e. CB₁IR <2 and ≥2. In microsatellite stable, but not microsatellite instable tumours (as adjudged on the basis of immunohistochemical determination of four mismatch repair proteins), there was a significant positive association of the tumour grade with the CB₁IR intensity. The difference between the microsatellite stable and instable tumours for this association of CB₁IR was related to the CpG island methylation status of the cases. Cox proportional hazards regression analyses indicated a significant contribution of CB₁IR to disease-specific survival in the microsatellite stable tumours when adjusting for tumour stage. For the cases with stage II microsatellite stable tumours, there was a significant effect of both tumour centre and front CB₁IR upon disease specific survival. The 5 year probabilities of event-free survival were: 85±5 and 66±8%; tumour interior, 86±4% and 63±8% for the CB₁IR<2 and CB₁IR≥2 groups, respectively.

Conclusions/Significance

The level of CB₁ receptor expression in colorectal cancer is associated with the tumour grade in a manner dependent upon the degree of CpG hypermethylation. A high CB₁IR is indicative of a poorer prognosis in stage II microsatellite stable tumour patients.

PIK3CA kinase domain mutation identifies a subgroup of stage III colon cancer patients with poor prognosis

BACKGROUND

PIK3CA mutations in the helical domain (in exon 9) and in the kinase domain (exon 20) cause tumor formation by different means. We aimed to determine the effects of each of these mutations on survival of colon carcinoma patients.

METHODS

A large cohort of 685 colon carcinoma patients was tested for PIK3CA mutations in exons 9 and 20 by single nucleotide primer extension (N = 428) or by real time PCR (N = 257).

RESULTS

PIK3CA mutation rate was 13%. 66 of 83 (79.5%) were in exon 9 and 17 of 83 (20.5%) in exon 20. In survival analysis, PIK3CA mutations in exon 9 and 20 had different effects on patient outcome. The PIK3CA exon 20 mutation conferred a poorer disease free survival compared to patients with wild type alleles and exon 9 mutations (Log rank p = 0.04 and p = 0.03 respectively) and cancer specific survival (Log rank p = 0.03 and p = 0.056 respectively) in stage III patients. In stage I and II this negative effect on outcome was not seen.

CONCLUSIONS

PIK3CA mutation in exon 20 is a negative prognostic factor in stage III colon cancer patients. Moreover, this negative effect is not present in stage I and II patients.

Association between deficient mismatch repair system and efficacy to irinotecan-containing chemotherapy in metastatic colon cancer

The present study investigated the association between deficient mismatch repair (dMMR) and efficacy outcomes of irinotecan-based first-line chemotherapy in patients with metastatic colorectal cancer (mCRC). Among 297 patients with sporadic mCRC receiving an irinotecan-containing regimen as first-line chemotherapy, 197 with available paraffin-embedded tissues were included in the current analysis. Tumors displaying loss of MMR protein (MLH1 or MSH2) and/or a microsatellite instability-high (MSI-H) genotype by PCR were classified as dMMR. Deficient mismatch repair was found in 23 evaluable tumors, among which eight displayed negativity for MLH1 expression, 11 for MSH2 expression, and four for both. The overall response rate was 47.2% (46.0% in proficient MMR (pMMR) and 56.5% in dMMR), with no significant difference between the two groups (P = 0.569). Median progression-free survival was 8.85 months in patients with dMMR tumors and 6.82 months in patients with pMMR tumors, but this difference did not reach statistical significance (P = 0.089). Median overall survival was not different between the two groups (P = 0.413). Efficacy outcomes of first-line irinotecan-based chemotherapy did not differ significantly between mCRC patients with pMMR and those with dMMR. Our data collectively indicate that MMR status is not effective as a single predictive marker for response to irinotecan-based chemotherapy in mCRC patients.