Association Between RAS/BRAF Mutations and Complete Response Following Total Neoadjuvant Therapy in Patients with Rectal Cancer: A Prospective Multicentered Study.

BACKGROUND: The impact of RAS/BRAF mutation on primary response rates after total neoadjuvant therapy (TNT) in patients with advanced rectal cancer is unclear. The aim of this study was to assess complete response rates after TNT according to RAS/BRAF mutation status. METHODS: A prospective observational study was performed in patients with rectal cancer who underwent TNT with curative intent at three South Australian hospitals between 2019 and 2023. Patients were classified according to their mutation status: mutant RAS/BRAF (mutRAS) or wild-type RAS/BRAF (wtRAS). The primary endpoint was overall complete response (oCR) rate, defined as the proportion of patients who achieved clinical complete response (cCR) and/or pathological complete response (pCR). RESULTS: Of the 150 patients eligible for inclusion, 80 patients with RAS/BRAF status available were identified. Of these, 43 (53.8%) patients were classified as mutRAS and 37 (46.3%) patients as wtRAS. Patients with mutRAS had significantly lower cCR and oCR rates after TNT than patients with wtRAS (14% vs. 37.8%, p = 0.014; 11.6% vs. 43.2%, p = 0.001, respectively). There was no significant difference in pCR rate between the groups. Of the 80 rectal cancer patients tested, 35 (43.8%) had metastatic disease (M1). There was no significant difference in complete M1 response rates between the groups (17.6% vs. 38.9%, p = 0.254). CONCLUSION: RAS/BRAF mutations negatively impact primary tumor response rates after TNT in patients with advanced rectal cancer. Large-scale national studies are needed to determine whether RAS/BRAF status could be used to select optimal oncologic therapy in rectal cancer patients.

Identification of microRNA Biomarkers of Response to Neoadjuvant Chemoradiotherapy in Esophageal Adenocarcinoma Using Next Generation Sequencing.

BACKGROUND: Clinical trials report improved overall survival following neoadjuvant chemoradiotherapy in patients undergoing surgery for esophageal adenocarcinoma, with a 10-15% survival improvement. MicroRNAs (miRNAs) are small noncoding RNAs that are known to direct the behavior of cancers, including response to treatment. We investigated the ability of miRNAs to predict outcomes after neoadjuvant chemoradiotherapy. METHODS: Endoscopic biopsies from esophageal adenocarcinomas were obtained before neoadjuvant chemoradiotherapy and esophagectomy. miRNA levels were measured in the biopsies using next generation sequencing and compared with pathological response in the surgical resection, and subsequent survival. miRNA ratios that predicted pathological response were identified by Lasso regression and leave-one-out cross-validation. Association between miRNA ratio candidates and relapse-free survival was assessed using Kaplan-Meier analysis. Cox regression and Harrell's C analyses were performed to assess the predictive performance of the miRNAs. RESULTS: Two miRNA ratios (miR-4521/miR-340-5p and miR-101-3p/miR-451a) that predicted the pathological response to neoadjuvant chemoradiotherapy were found to be associated with relapse-free survival. Pretreatment expression of these two miRNA ratios, pretreatment tumor differentiation, posttreatment AJCC histopathological tumor regression grading, and posttreatment tumor clearance/margins were significant factors associated with survival in Cox regression analysis. Multivariate analysis of the two ratios together with pretherapy factors resulted in a risk prediction accuracy of 85% (Harrell's C), which was comparable with the prediction accuracy of the AJCC treatment response grading (77%). CONCLUSIONS: miRNA-ratio biomarkers identified using next generation sequencing can be used to predict disease free survival following neoadjuvant chemoradiotherapy and esophagectomy in patients with esophageal adenocarcinoma.

Androgen Receptor and Androgen-Responsive Gene FKBP5 Are Independent Prognostic Indicators for Esophageal Adenocarcinoma.

BACKGROUND: Esophageal adenocarcinoma is a male-dominant disease, but the role of androgens is unclear. AIMS: To examine the expression and clinical correlates of the androgen receptor (AR) and the androgen-responsive gene FK506-binding protein 5 (FKBP5) in esophageal adenocarcinoma. METHODS: Expression of AR and FKBP5 was determined by immunohistochemistry. The effect of the AR ligand 5α-dihydrotestosterone (DHT) on the expression of a panel of androgen-responsive genes was measured in AR-positive and AR-negative esophageal adenocarcinoma cell lines. Correlations in expression between androgen-responsive genes were analyzed in an independent cohort of esophageal adenocarcinoma tissues. RESULTS: There was AR staining in 75 of 77 cases (97 %), and FKBP5 staining in 49 (64 %), all of which had nuclear AR. Nuclear AR with FKBP5 expression was associated with decreased median survival (451 vs. 2800 days) and was an independent prognostic indicator (HR 2.894, 95 % CI 1.396­6.002, p = 0.0043) in multivariable Cox proportional hazards models. DHT induced a significant increase in expression of the androgen-responsive genes FKBP5, HMOX1, FBXO32, VEGFA, WNT5A, and KLK3 only in AR-positive cells in vitro. Significant correlations in expression were observed between these androgen-responsive genes in an independent cohort of esophageal adenocarcinoma tissues. CONCLUSION: Nuclear AR and expression of FKBP5 is associated with decreased survival in esophageal adenocarcinoma.

Wild-type APC predicts poor prognosis in microsatellite-stable proximal colon cancer.

BACKGROUND: APC mutations (APC-mt) occur in ∼70% of colorectal cancers (CRCs), but their relationship to prognosis is unclear. METHODS: APC prognostic value was evaluated in 746 stage I-IV CRC patients, stratifying for tumour location and microsatellite instability (MSI). Microarrays were used to identify a gene signature that could classify APC mutation status, and classifier ability to predict prognosis was examined in an independent cohort. RESULTS: Wild-type APC microsatellite stable (APC-wt/MSS) tumours from the proximal colon showed poorer overall and recurrence-free survival (OS, RFS) than APC-mt/MSS proximal, APC-wt/MSS distal and APC-mt/MSS distal tumours (OS HR⩾1.79, P⩽0.015; RFS HR⩾1.88, P⩽0.026). APC was a stronger prognostic indicator than BRAF, KRAS, PIK3CA, TP53, CpG island methylator phenotype or chromosomal instability status (P⩽0.036). Microarray analysis similarly revealed poorer survival in MSS proximal cancers with an APC-wt-like signature (P=0.019). APC status did not affect outcomes in MSI tumours. In a validation on 206 patients with proximal colon cancer, APC-wt-like signature MSS cases showed poorer survival than APC-mt-like signature MSS or MSI cases (OS HR⩾2.50, P⩽0.010; RFS HR⩾2.14, P⩽0.025). Poor prognosis APC-wt/MSS proximal tumours exhibited features of the sessile serrated neoplasia pathway (P⩽0.016). CONCLUSIONS: APC-wt status is a marker of poor prognosis in MSS proximal colon cancer.

Her-2/neu gene amplification in esophageal adenocarcinoma and its influence on survival.

BACKGROUND: HER-2/neu (c-erbB-2, HER2) gene amplification and protein overexpression have been associated with poor prognosis in several solid tumors, including breast and gastric cancer. Its incidence and significance in esophageal adenocarcinoma is unknown. MATERIALS AND METHODS: Tissue microarrays were successfully constructed from 89 paraffin-embedded archival specimens of esophageal adenocarcinomas for HER2 gene amplification by silver-enhanced in situ hybridization (SISH). No patients had undergone neoadjuvant therapy. Protein overexpression was tested with immunohistochemistry (IHC) using automated immunostaining (Ventana Benchmark). Incidence of HER2 positivity, correlation to clinicopathological variables in esophageal cancer patients, and concordance between SISH and IHC were determined. RESULTS: True HER2 gene amplification was detected in 14 esophageal cancer specimens (16%), and 92% of those with high-level HER2 amplification showed positive HER2 protein overexpression. No significant associations were found among gene amplification and clinicopathological factors. The 5-year survival rates were 57% for esophageal cancer patients with HER2 amplification compared with 32% without, but the difference in overall survival was not significant (P = .37). The correlation between SISH and IHC was statistically significant (P < .0001). CONCLUSION: While molecular targeting may be possible for approximately 16% of esophageal adenocarcinoma patients, HER2 oncogene amplification did not influence survival in this study.

Feasibility study of sentinel lymph node biopsy in esophageal cancer with conservative lymphadenectomy.

INTRODUCTION: Lymphoscintigraphy and sentinel node mapping is established in breast cancer and melanoma but not in esophageal cancer, even though many centers have shown that occult tumor deposits in lymph nodes influence prognosis. We report our initial experience with lymphoscintigraphy and sentinel lymph node biopsy in patients undergoing resection for esophageal cancer. METHODS: Sixteen of 17 consecutive patients underwent resection for invasive esophageal cancer along with sentinel lymph node retrieval (resection rate, 94%). Peritumoral injection of (99m)Tc antimony colloid was performed by upper endoscopy prior to the operation. A two-surgeon synchronous approach via right thoracotomy and laparotomy was performed with conservative lymphadenectomy. Sentinel lymph nodes were identified using a gamma probe both in vivo and ex vivo. Sentinel lymph nodes were sent off separately for serial sections and immunohistochemistry. RESULTS: Median patient age was 60.4 years (range, 45-75 years). Fifteen were male, and thirteen had adenocarcinoma. At least one sentinel lymph node (median, 2) was identified in 14 of 16 patients (success rate, 88%). Sentinel nodes were present in more than one nodal station in five patients (31%). In all 14 patients, the sentinel lymph node accurately predicted findings in non-sentinel nodes (accuracy, 100%). Three patients with positive sentinel lymph nodes had metastases identified in non-sentinel nodes (sensitivity, 100%). CONCLUSIONS: Sentinel lymph node biopsy is feasible in esophageal resection with conservative lymphadenectomy, and initial results suggest it is accurate in predicting overall nodal status. Further study is needed to assess impact on patient management and prognosis.

Young-onset colorectal cancer is associated with a personal history of type 2 diabetes.

BACKGROUND: Colorectal cancer (CRC) is rising in incidence in young adults, and this observation is currently unexplained. We investigated whether having a personal history of type 2 diabetes mellitus (T2D) was a potential risk factor for young-onset colorectal cancer (YOCRC). METHODS: The South Australian Young Onset (SAYO) CRC study is a series of young adults with CRC below age 55. Ninety unrelated YOCRC cases were recruited to the study. Personal history and detailed family history of T2D were obtained at face-to-face interview and confirmed from medical records. Whole exome sequencing was conducted on germline DNA from each CRC case. Controls for personal history studies of T2D were 240 patients with proven clear colonoscopies and no known CRC predispositions. RESULTS: The median age of YOCRC cases was 44 years (18-54) and of controls was 45 years (18-54), and 53% of both cases and controls were females (P = 0.99). Left-sided (distal) CRC was seen in 67/89 (75%) of cases. A personal history of T2D was confirmed in 17/90 (19%) YOCRC patients compared with controls (12/240, 5%; P < 0.001; odds ratio = 4.4; 95% confidence interval, 2.0-9.7). YOCRC patients frequently reported at least one first-degree relative with T2D (32/85, 38%). Ten of 87 (12%) of YOCRC cases had CRC-related pathogenic germline variants, however, no pathogenic variants in familial diabetes-associated genes were seen. CONCLUSIONS: Though the mechanism remains unclear, our observations suggest that there is enrichment for personal history of T2D in YOCRC patients. IMPACT: A diagnosis of T2D could therefore potentially identify a subset of young adults at increased risk for CRC and in whom early screening might be appropriate.

Isolated tumor cells in esophageal cancer: implications for the surgeon and the pathologist.

INTRODUCTION: Studies suggest that up to 56% of node-negative patients have tumor deposits in their lymph nodes that are missed by routine pathologic examination. However, few studies differentiate between isolated tumor cells and micrometastases using reproducible criteria, and their prognostic significance has not been established. METHODS: We identified 119 patients who had undergone surgical resection for esophageal cancer between 1997 and 2007, and who were classified as node-negative. Relevant paraffin blocks were identified, and 3 additional levels, each 250 mum apart, were cut of all lymph nodes. Isolated tumor cells and micrometastases were defined according to size criteria but additional data and characteristics were recorded. Two slides were made at each level (1 for hematoxylin and eosin, 1 for immunohistochemistry). Results were correlated with survival. RESULTS: One patient was found to have a metastasis (>2 mm), 8 patients (7%) had micrometastases, and 22 patients (18%) had isolated tumor cells. The 5-year survival rates were 60% for patients who remained node-negative, 33% for patients with isolated tumor cells, 40% for patients with micrometastases, and 0 for the patient with a metastasis (P = 0.02). A significant difference was found between node-negative patients versus patients whose lymph nodes contained isolated tumor cells (P = 0.014). Most tumor deposits (71%) were identified on the first additional section. CONCLUSIONS: Our results suggest that isolated tumor cells are as important as micrometastases in determining survival in patients with esophageal cancer. This has important implications in the retrieval and pathologic analysis of lymph nodes.

Similarity of aberrant DNA methylation in Barrett's esophagus and esophageal adenocarcinoma.

BACKGROUND: Barrett's esophagus (BE) is the metaplastic replacement of squamous with columnar epithelium in the esophagus, as a result of reflux. It is the major risk factor for the development of esophageal adenocarcinoma (EAC). Methylation of CpG dinucleotides of normally unmethylated genes is associated with silencing of their expression, and is common in EAC. This study was designed to determine at what stage, in the progression from BE to EAC, methylation of key genes occurs. RESULTS: We examined nine genes (APC, CDKN2A, ID4, MGMT, RBP1, RUNX3, SFRP1, TIMP3, and TMEFF2), frequently methylated in multiple cancer types, in a panel of squamous (19 biopsies from patients without BE or EAC, 16 from patients with BE, 21 from patients with EAC), BE (40 metaplastic, seven high grade dysplastic) and 37 EAC tissues. The methylation frequency, the percentage of samples that had any extent of methylation, for each of the nine genes in the EAC (95%, 59%, 76%, 57%, 70%, 73%, 95%, 74% and 83% respectively) was significantly higher than in any of the squamous groups. The methylation frequency for each of the nine genes in the metaplastic BE (95%, 28%, 78%, 48%, 58%, 48%, 93%, 88% and 75% respectively) was significantly higher than in the squamous samples except for CDKN2A and RBP1. The methylation frequency did not differ between BE and EAC samples, except for CDKN2A and RUNX3 which were significantly higher in EAC. The methylation extent was an estimate of both the number of methylated alleles and the density of methylation on these alleles. This was significantly greater in EAC than in metaplastic BE for all genes except APC, MGMT and TIMP3. There was no significant difference in methylation extent for any gene between high grade dysplastic BE and EAC. CONCLUSION: We found significant methylation in metaplastic BE, which for seven of the nine genes studied did not differ in frequency from that found in EAC. This is also the first report of gene silencing by methylation of ID4 in BE or EAC. This study suggests that metaplastic BE is a highly abnormal tissue, more similar to cancer tissue than to normal epithelium.

Improving the accuracy of TNM staging in esophageal cancer: a pathological review of resected specimens.

BACKGROUND: Controversy exists over the Sixth Edition of the International Union Against Cancer (UICC) TNM staging system for esophageal cancer. Inclusion of additional information such as the number of metastatic lymph nodes and extracapsular lymph node invasion may improve the current staging system and lead to optimization of patient treatment. METHODS: All patients in Adelaide who underwent resection for esophageal cancer between 1997 and 2007 were identified from a prospective database. Two independent observers then reexamined all pathology slides from the original resection. Univariate and multivariate analysis was performed to identify significant prognostic factors. The goodness of fit and accuracy of additional prognostic factors were assessed, and the staging system was modified according to this information. RESULTS: There were 240 patients (mean age, 62 years) who met the inclusion criteria. The 5-year overall survival rate was 36% (median, 24 months). Only histological grade and a refined pN stage were found to be independent prognostic factors that could then be used to improve current TNM staging. Subdivision of pN stage into three groups (0, 1-2, and >2 positive nodes) showed significant differences in 5-year survival between all three groups: 53% vs 27% vs 6%, respectively (P < .01). The optimal staging model was the same for patients who received neoadjuvant therapy and surgery (n = 116), and those who underwent surgery alone (n = 124). CONCLUSION: A staging model that incorporates a refined pN stage and histological grade appears to be more accurate than the current UICC-TNM staging system. This staging model is still applicable in patients who receive neoadjuvant therapy.

Methylation of TIMP3 in esophageal squamous cell carcinoma.

AIM: To measure the frequency of DNA methylation of the tissue inhibitor of metalloproteinase 3 (TIMP3) promoter and relate this to any change of gene expression in esophageal squamous cell carcinoma in patients from a region of high incidence in China. METHODS: Cancer cell lines were treated with or without the demethylating reagent 5-aza-2'-deoxycytidine. Methylation of the TIMP3 promoter was assessed in three regions by melt curve analysis and its expression was assessed by real-time RT-PCR. Tumors and proximal resection margins were obtained from 64 patients with esophageal squamous cell carcinoma from a region of high incidence in China. Methylation was assessed by melt curve analysis and expression by immunohistochemistry. RESULTS: Methylation in one of the three promoter regions assessed correlated with gene silencing in esophageal cell lines. A degree of methylation of TIMP3 was found in only four esophageal squamous cell carcinomas, and partial loss of TIMP3 protein expression in just one. CONCLUSION: Methylation and loss of expression of TIMP3 occurs infrequently in esophageal squamous cell carcinoma in a region of high incidence in China.

Isolated loss of PMS2 expression in colorectal cancers: frequency, patient age, and familial aggregation.

PURPOSE: Most colorectal cancers that have high levels of microsatellite instability (MSI-H) show loss of immunohistochemical expression of proteins that participate in the DNA mismatch repair process, most often involving MLH1 and MSH2. Less commonly, a third DNA mismatch repair protein, MSH6, may also be lost as the primary event. Rarely, tumors with MSI-H show normal expression of these three proteins. The genetic deficiency leading to the MSI-H phenotype in such cases is unknown. PMS2 is another member of the DNA mismatch repair complex. Its expression is generally lost in tumors with MLH1 loss of expression. Rarely, there is selective loss of PMS2 expression. We sought to describe the frequency and clinical correlates of selective loss of expression of PMS2 with the MSI-H tumor phenotype. EXPERIMENTAL DESIGN: Two thousand seven hundred nineteen colorectal cancers from both clinic- and research-based ascertainment were studied. Tumor MSI testing and immunohistochemistry for MLH1, MSH2, MSH6, and PMS2 were conducted. Medical records were abstracted for age at diagnosis, gender, colorectal cancer site, and family history. RESULTS: Five hundred thirty-five of the 2,719 tumors were MSI-H. Of these, 93% showed loss of expression of MLH1, MSH2, and/or MSH6. Thirty-eight showed normal expression for these proteins. PMS2 immunohistochemical staining was successful in 32 of 38 of these tumors. Of the 32, 23 showed selective loss of expression of PMS2. This was associated with young age of diagnosis and right-sided location but not with a striking family history of cancer. CONCLUSIONS: Overall, 97% of the MSI-H tumors showed loss of expression for one or more of these four mismatch repair proteins. Selective loss of expression of PMS2 was present in 72% of cases in which colorectal cancers had an MSI-H phenotype but no alteration of expression of MLH1, MSH2, and MSH6. The underlying mechanism involved cannot be determined from this study but could involve point mutations in other DNA mismatch repair genes with retention of immunohistochemical expression, somatic inactivation of PMS2, or germ line mutation of PMS2.

Metallothionien 3 expression is frequently down-regulated in oesophageal squamous cell carcinoma by DNA methylation.

BACKGROUND: Metallothionein 3 (MT3) inhibits growth in a variety of cell types. We measured MT3 gene expression by RT-PCR, and DNA methylation in the MT3 promoter by combined bisulphite restriction analysis, in four oesophageal cancer cell lines and the resected oesophagus from 64 patients with oesophageal squamous cell carcinoma (SCC). RESULTS: MT3 expression was not detected in one of the four oesophageal cell lines. The MT3 promoter was methylated in all of the oesophageal cell lines, but the degree of methylation was greater in the non-expressing cell line. After treatment with 5-aza-2'-deoxycytidine there was a reduction in the degree of methylation, and an increase in MT3 expression, in each of the cell lines (p < 0.01). Methylation was detected in 52% (33 of 64) of primary SCC and 3% (2 of 62) of histologically normal resection margins. MT3 expression was measured in 29 tumours, 17 of which had methylation of MT3. The expression of MT3 was significantly less in the methylated tumours compared to either the unmethylated tumours (p = 0.03), or the matched margin (p = 0.0005). There was not a significant difference in MT3 expression between the tumour and the margin from patients with unmethylated tumour. No correlations were observed between methylation of MT3 and survival time, patient age, gender, smoking or drinking history, tumour stage, volume, or lymph node involvement. CONCLUSION: We conclude that MT3 expression is frequently down-regulated in oesophageal SCC, by DNA methylation, but that this is not a prognostic indicator.

Clinicopathological predictors of benefit from adjuvant chemotherapy for stage C colorectal cancer: Microsatellite unstable cases benefit.

AIM: In colorectal cancer (CRC), adjuvant therapy is offered on the basis of stage and attempts to identify factors to better target treatment have not been successful. Recent work suggested that mismatch repair deficient CRCs may not benefit from 5FU adjuvant chemotherapy but studies remain conflicting. We aimed to determine if gender, tumor site, tumor pathological characteristics and microsatellite instability (MSI) predict survival benefit from adjuvant chemotherapy in stage C CRC. METHODS: Data were collated on ACPS (Australian Clinico-pathological Staging System) stage C CRC cases that underwent curative resection over a 23-year period. Pathology was reevaluated, DNA was extracted from the formalin-fixed paraffin specimen, and MSI status was established by BAT26 instability. Multivariate analysis was performed using Cox proportional hazard model and effects modification interaction testing. RESULTS: In total 814 unselected cases were included, of whom 37% received chemotherapy. Seventy-seven cases exhibited MSI. Overall, adjuvant chemotherapy produced a cancer-specific survival benefit (HR 0.52, 95% CI 0.39-0.70; P < 0.0001). On interaction testing, none of the examined parameters significantly influenced the magnitude of that survival benefit. Chemotherapy was beneficial in both the MSI (HR 0.08, 95% CI 0.02-0.27; P = < 0.0001) and the microsatellite stable cohort (HR 0.62, 95% CI 0.47-0.81; P = 0.001). CONCLUSION: These results suggest that survival benefit from 5FU adjuvant chemotherapy for stage C CRC does not vary according to gender, site of tumor, pathological characteristics or MSI status. This study suggests that it would be unwise to exclude patients from being offered adjuvant chemotherapy on the basis of MSI.

PIK3CA and PTEN gene and exon mutation-specific clinicopathologic and molecular associations in colorectal cancer.

PURPOSE: PIK3CA and PTEN mutations are prevalent in colorectal cancer and potential markers of response to mitogen-activated protein/extracellular signal-regulated kinase inhibitors and anti-EGF receptor antibody therapy. Relationships between phosphoinositide 3-kinase (PI3K) pathway mutation, clinicopathologic characteristics, molecular features, and prognosis remain controversial. EXPERIMENTAL DESIGN: A total of 1,093 stage I-IV colorectal cancers were screened for PIK3CA (exons 9 and 20), KRAS (codons 12-13), BRAF (codon 600) mutations, and microsatellite instability (MSI). PTEN (exons 3-8) and CpG island methylator phenotype (CIMP) status were determined in 744 and 489 cases. PIK3CA data were integrated with 17 previous reports (n = 5,594). RESULTS: PIK3CA and PTEN mutations were identified in 11.9% and 5.8% of colorectal cancers. PTEN mutation was associated with proximal tumors, mucinous histology, MSI-high (MSI-H), CIMP-high (CIMP-H), and BRAF mutation (P < 0.02). PIK3CA mutation was related to older age, proximal tumors, mucinous histology, and KRAS mutation (P < 0.04). In integrated cohort analysis, PIK3CA exon 9 and 20 mutations were overrepresented in proximal, CIMP-low (CIMP-L), and KRAS-mutated cancers (P ≤ 0.011). Comparing PIK3CA exonic mutants, exon 20 mutation was associated with MSI-H, CIMP-H, and BRAF mutation, and exon 9 mutation was associated with KRAS mutation (P ≤ 0.027). Disease-free survival for stage II/III colorectal cancers did not differ by PI3K pathway status. CONCLUSION: PI3K pathway mutation is prominent in proximal colon cancers, with PIK3CA exon 20 and PTEN mutations associated with features of the sessile-serrated pathway (MSI-H/CIMP-H/BRAF(mut)), and PIK3CA exon 9 (and to a lesser extent exon 20) mutation associated with features of the traditional serrated pathway (CIMP-L/KRAS(mut)) of tumorigenesis. Our data highlight the PI3K pathway as a therapeutic target in distinct colorectal cancer subtypes.

SMAD2, SMAD3 and SMAD4 mutations in colorectal cancer.

Activation of the canonical TGF-ß signaling pathway provides growth inhibitory signals in the normal intestinal epithelium. Colorectal cancers (CRCs) frequently harbor somatic mutations in the pathway members TGFBR2 and SMAD4, but to what extent mutations in SMAD2 or SMAD3 contribute to tumorigenesis is unclear. A cohort of 744 primary CRCs and 36 CRC cell lines were sequenced for SMAD4, SMAD2, and SMAD3 and analyzed for allelic loss by single-nucleotide polymorphism (SNP) microarray analysis. Mutation spectra were compared between the genes, the pathogenicity of mutations was assessed, and relationships with clinicopathologic features were examined. The prevalence of SMAD4, SMAD2, and SMAD3 mutations in sporadic CRCs was 8.6% (64 of 744), 3.4% (25 of 744), and 4.3% (32 of 744), respectively. A significant overrepresentation of two genetic hits was detected for SMAD4 and SMAD3, consistent with these genes acting as tumor suppressors. SMAD4 mutations were associated with mucinous histology. The mutation spectra of SMAD2 and SMAD3 were highly similar to that of SMAD4, both in mutation type and location within the encoded proteins. In silico analyses suggested the majority of the mutations were pathogenic, with most missense changes predicted to reduce protein stability or hinder SMAD complex formation. The latter altered interface residues or disrupted the phosphorylation-regulated Ser-Ser-X-Ser motifs within SMAD2 and SMAD3. Functional analyses of selected mutations showed reductions in SMAD3 transcriptional activity and SMAD2-SMAD4 complex formation. Joint biallelic hits in SMAD2 and SMAD3 were overrepresented and mutually exclusive to SMAD4 mutation, underlining the critical roles of these three proteins within the TGF-ß signaling pathway.

Analysis of families with Lynch syndrome complicated by advanced serrated neoplasia: the importance of pathology review and pedigree analysis.

The identification of Lynch syndrome has been greatly assisted by the advent of tumour immunohistochemistry (IHC) for mismatch repair (MMR) proteins, and by the recognition of the role of acquired somatic BRAF mutation in sporadic MMR-deficient colorectal cancer (CRC). However, somatic BRAF mutation may also be present in the tumours in families with a predisposition to develop serrated polyps in the colorectum. In a subgroup of affected members in these families, CRCs emerge which demonstrate clear evidence of MMR deficiency with absent MLH1 staining and high-level microsatellite instability (MSI). This may result in these families being erroneously classified as Lynch syndrome, or conversely, an individual is considered "sporadic" due to the presence of a somatic BRAF mutation in a tumour. In this report, we describe two Lynch syndrome families who demonstrated several such inconsistencies. In one family, IHC deficiency of both MSH2 and MLH1 was demonstrated in tumours from different affected family members, presenting a confusing diagnostic picture. In the second family, MLH1 loss was observed in the lesions of both MLH1 mutation carriers and those who showed normal MLH1 germline sequence. Both families had Lynch syndrome complicated by an independently segregating serrated neoplasia phenotype, suggesting that in families such as these, tumour and germline studies of several key members, rather than of a single proband, are indicated to clarify the spectrum of risk.

Pathology features in Bethesda guidelines predict colorectal cancer microsatellite instability: a population-based study.

BACKGROUND & AIMS: The revised Bethesda guidelines for Lynch syndrome recommend microsatellite instability (MSI) testing all colorectal cancers in patients diagnosed before age 50 years and colorectal cancers diagnosed in patients between ages 50 and 59 years with particular pathology features. Our aim was to identify pathology and other features that independently predict high MSI (MSI-H). METHODS: Archival tissue from 1098 population-based colorectal cancers diagnosed before age 60 years was tested for MSI. Pathology features, site, and age at diagnosis were obtained. Multiple logistic regression was performed to determine the predictive value of each feature, as measured by an odds ratio (OR), from which a scoring system (MsPath) was developed to estimate the probability a colorectal cancer is MSI-H. RESULTS: Fifteen percent of tumors (162) were MSI-H. Independent predictors were tumor-infiltrating lymphocytes (OR, 9.1; 95% confidence interval [CI], 5.9-14.1), proximal subsite (OR, 4.7; 95% CI, 3.1-7.3), mucinous histology (OR, 2.8; 95% CI, 1.7-4.8), poor differentiation (OR, 1.9; 95% CI, 1.2-3.1), Crohn's-like reaction (OR, 1.9; 95% CI, 1.2-2.9), and diagnosis before age 50 years (OR, 1.9; 95% CI, 1.3-2.9). MsPath score >or=1.0 had a sensitivity of 93% and a specificity of 55% for MSI-H. CONCLUSIONS: The probability an individual colorectal cancer is MSI-H is predicted well by the MsPath score. There is little value in testing for DNA mismatch repair loss in tumors, or for germline mismatch repair mutations, for colorectal cancers diagnosed in patients before age 60 years with an MSPath score <1 (approximately 50%). Pathology can identify almost all MSI-H colorectal cancers diagnosed before age 60 years.