GNAS mutation inhibits growth and induces phosphodiesterase 4D expression in colorectal cancer cell lines.

Approximately 5% of colorectal cancers (CRCs) have a gain-of-function mutation in the GNAS gene, which leads to the activation of cAMP-dependent signaling pathways and associates with poor prognosis. We investigated the effect of an activating GNAS mutation in CRC cell lines on gene expression and cell proliferation in vitro, and tumor growth in vivo. GNAS-mutated (GNASmt) HCT116 cells showed stimulated synthesis of cAMP as compared to parental (Par) cells. The most upregulated gene in the GNASmt cells was cAMP-hydrolyzing phosphodiesterase 4D (PDE4D) as detected by RNA sequencing. To further validate our finding, we analyzed PDE4D expression in a set of human CRC tumors (n = 35) and demonstrated overexpression in GNAS mutant CRC tumors as compared to GNAS wild-type tumors. The GNASmt HCT116 cells proliferated more slowly than the Par cells. PDE4 inhibitor Ro 20-1724 and PDE4D subtype selective inhibitor GEBR-7b further suppressed the proliferation of GNASmt cells without an effect on Par cells. The growth inhibitory effect of these inhibitors was also seen in the intrinsically GNAS-mutated SK-CO-1 CRC cell line having high levels of cAMP synthesis and PDE4D expression. In vivo, GNASmt HCT116 cells formed smaller tumors than the Par cells in nude mice. In conclusion, our findings demonstrate that GNAS mutation results in the growth suppression of CRC cells. Moreover, the GNAS mutation-induced overexpression of PDE4D provides a potential avenue to impede the proliferation of CRC cells through the use of PDE4 inhibitors.

Atypical (non-V600E) BRAF mutations in metastatic colorectal cancer in population and real-world cohorts.

BRAF-V600E mutation (mt) is a strong negative prognostic and predictive biomarker in metastatic colorectal cancer (mCRC). Non-V600Emt, designated atypical BRAFmt (aBRAFmt) are rare, and little is known about their frequency, co-mutations and prognostic and predictive role. These were compared between mutational groups of mCRC patients collected from three Nordic population-based or real-world cohorts. Pathology of aBRAFmt was studied. The study included 1449 mCRC patients with 51 (3%) aBRAFmt, 182 (13%) BRAF-V600Emt, 456 (31%) RAS&BRAF wild-type (wt) and 760 (52%) RASmt tumours. aBRAFmt were seen in 2% of real-world and 4% of population-based cohorts. Twenty-six different aBRAFmt were detected, 11 (22%) class 2 (serrated adenocarcinoma in 2/9 tested), 32 (64%) class 3 (serrated in 15/25) and 4 (8%) unclassified. aBRAFmt patients were predominantly male, had more rectal primaries, less peritoneal metastases, deficient mismatch repair in one (2%), and better survival after metastasectomy (89% 5-year overall survival [OS]-rate) compared with BRAF-V600Emt. aBRAFmt and BRAF-V600Emt had poorer performance status and received fewer treatment lines than RAS&BRAFwt and RASmt. OS among aBRAFmt (median 14.4 months) was longer than for BRAF-V600Emt (11.2 months), but shorter than for RAS&BRAFwt (30.5 months) and RASmt (23.4 months). Addition of bevacizumab trended for better OS for the aBRAFmt. Nine patients with aBRAFmt received cetuximab/panitumumab without response. aBRAFmt represents a distinct subgroup differing from other RAS/BRAF groups, with serrated adenocarcinoma in only half. OS for patients with aBRAFmt tumours was slightly better than for BRAF-V600Emt, but worse than for RASmt and RAS&BRAFwt. aBRAFmt should not be a contraindication for metastasectomy.

Postoperative Complications After Neoadjuvant Chemotherapy Versus Upfront Surgery in Gastric Adenocarcinoma: A Population-Based Nationwide Study in Finland.

BACKGROUND: To date, no large population-based studies have compared complications and short-term outcomes between neoadjuvant chemotherapy and upfront surgery in gastric cancer. More nationwide studies with standardized reporting on complications are needed to enable international comparison between studies. This study aimed to compare postoperative complications between neoadjuvant therapy and upfront surgery after gastrectomy for gastric adenocarcinoma in a population-based setting. METHODS: This population-based study based on the Finnish National Esophago-Gastric Cancer Cohort included all patients 18 years of age or older undergoing gastrectomy for gastric adenocarcinoma in Finland during 2005-2016. Logistic regression provided odds ratios (ORs) with 95% confidence intervals (CIs), both crude and adjusted for key confounders. Different types of complications were graded based on the Esophagectomy Complications Consensus Group definitions, and major complications were assessed by the Clavien-Dindo scale. RESULTS: This study analyzed 769 patients. Neoadjuvant chemotherapy did not increase major postoperative complications after gastrectomy for gastric cancer compared with upfront surgery (OR, 1.12; 95% CI 0.81-1.56). Furthermore, it did not increase pneumonia, anastomotic complications, wound complications, or other complications. CONCLUSIONS: Neoadjuvant therapy is not associated with increased postoperative complications, reoperations, or short-term mortality compared with upfront surgery in gastric adenocarcinoma.

Comparison of Postoperative Complications After Gastrectomy for Gastric Cancer with Antecolic Versus Retrocolic Reconstruction: A Population-Based Study.

BACKGROUND: The purpose of this study was to examine the rates of 90-day anastomotic complications and other postoperative complications after total or partial gastrectomy with antecolic versus retrocolic reconstruction in a population-based setting. METHODS: This population-based nationwide retrospective cohort study included all patients undergoing total or partial gastrectomy for gastric adenocarcinoma in Finland in 2005-2016, with follow-up until 31 December 2019. Logistic regression provided odds ratios (ORs) with 95% confidence intervals (CIs) of 90-day mortality. Results were adjusted for age, sex, year of the surgery, comorbidities, tumor locations, pathological stage, and neoadjuvant therapy. RESULTS: A total of 2063 patients having gastrectomy with antecolic (n = 814) or retrocolic (n = 1249) reconstruction were identified from the registries. The anastomotic complication rate was 3.8% with antecolic reconstruction and 5.0% with retrocolic reconstruction. Antecolic reconstruction was not associated with a higher risk of anastomotic complications compared with retrocolic reconstruction in the adjusted analysis (OR 0.69, 95% CI 0.44-1.09) of the whole cohort or in the predefined subgroups. The reoperation rate was 8.2% with antecolic reconstruction and 7.7% with retrocolic reconstruction, without statistical significance. In subgroup analysis of total gastrectomy patients, the risk of major complications was lower with antecolic reconstruction compared with retrocolic reconstruction (OR 0.62, 95% CI 0.45-0.86). CONCLUSIONS: The rate of anastomotic complications did not differ after antecolic versus retrocolic reconstruction after total or partial gastrectomy. In total gastrectomies, the risk of major complications was lower after antecolic compared with retrocolic reconstruction.

Novel insights into tumorigenesis revealed by molecular analysis of Lynch syndrome cases with multiple colorectal tumors.

Background: Lynch syndrome (LS) is an autosomal dominant multi-organ cancer syndrome with a high lifetime risk of cancer. The number of cumulative colorectal adenomas in LS does not generally exceed ten, and removal of adenomas via routine screening minimizes the cancer burden. However, abnormal phenotypes may mislead initial diagnosis and subsequently cause suboptimal treatment. Aim: Currently, there is no standard guide for the care of multiple colorectal adenomas in LS individuals. We aimed to shed insight into the molecular features and reasons for multiplicity of adenomas in LS patients. Methods: We applied whole exome sequencing on nine adenomas (ten samples) and three assumed primary carcinomas (five samples) of an LS patient developing the tumors during a 21-year follow-up period. We compared the findings to the tumor profiles of two additional LS cases ascertained through colorectal tumor multiplicity, as well as to ten adenomas and 15 carcinomas from 23 unrelated LS patients with no elevated adenoma burden from the same population. As LS associated cancers can arise via several molecular pathways, we also profiled the tumors for CpG Island Methylator Phenotype (CIMP), and LINE-1 methylation. Results: All tumors were microsatellite unstable (MSI), and MSI was present in several samples derived from normal mucosa as well. Interestingly, frequent frameshift variants in RNF43 were shared among substantial number of the tumors of our primary case and the tumors of LS cases with multiple tumors but almost absent in our control LS cases. The RNF43 variants were completely absent in the normal tissue, indicating tumor-associated mutational hotspots. The RNF43 status correlated with the mutational signature SBS96. Contrary to LS tumors from the reference set with no elevated colorectal tumor burden, the somatic variants occurred significantly more frequently at C>T in the CpG context, irrespective of CIMP or LINE-1 status, potentially indicating other, yet unknown methylation-related mechanisms. There were no signs of somatic mosaicism affecting the MMR genes. Somatic variants in APC and CTNNB1 were unique to each tumor. Conclusion: Frequent somatic RNF43 hot spot variants combined with SBS96 signature and increased tendency to DNA methylation may contribute to tumor multiplicity in LS.

Stapled vs handsewn anastomosis and anastomotic leaks in gastric cancer surgery-a population-based nationwide study in Finland.

BACKGROUND: There is a lack of evidence regarding anastomotic technique and postoperative complications in gastric cancer surgery. This study aimed to evaluate whether there are differences between stapled and handsewn anastomosis and anastomotic leaks. METHODS: This was a population-based, retrospective, nationwide cohort study in Finland using the Finnish National Esophago-Gastric Cancer Cohort. Patients undergoing gastrectomy with available postoperative complication data were included. Logistic regression analysis was used to calculate the odds ratios with 95% CIs, adjusted for calendar period of surgery, age at surgery, sex, comorbidity, tumor stage, neoadjuvant therapy, minimally invasive surgery, type of gastrectomy, radical resection, and type of anastomosis. RESULTS: Of the 2164 patients, 472 of all patients (21.8%) had handsewn anastomosis and 1692 of all patients (78.2%) had stapled anastomosis. In the unadjusted analysis, anastomotic leaks were significantly lower in the handsewn group (hazard ratio [HR], 0.42; 95% CI, 0.22-0.79) than the stapled group, but after adjustment for known prognostic factors, this association was no longer significant (HR, 0.57; 95% CI, 0.27-1.21). In the analysis stratified by gastrectomy type (distal or total), no differences in anastomotic leaks were observed between anastomotic techniques. CONCLUSION: In this population-based nationwide study, anastomotic technique (stapled or handsewn) was not associated with anastomotic leaks in any, distal or total, gastrectomy.

Postoperative delayed emptying after total, subtotal, or distal gastrectomy for gastric cancer: a population-based study.

BACKGROUND: This study aimed to examine the rate of delayed emptying and other 90-day postoperative complications after total, subtotal, and distal gastrectomies for gastric adenocarcinoma in a population-based setting. METHODS: This study included all patients who underwent total, subtotal, or distal gastrectomy for gastric cancer in Finland in 2005-2016, with follow-up until December 31, 2019. Logistic regression provided the odds ratios with 95% CIs of 90-day mortality. The results were adjusted for age, sex, year of surgery, comorbidities, pathologic stage, and neoadjuvant therapy. RESULTS: A total of 2058 patients underwent total (n = 1227), subtotal (n = 450), or distal (n = 381) gastrectomy. In the total, subtotal, and distal gastrectomy groups, the rates of 90-day delayed emptying were 1.7%, 1.3%, and 2.1% in the whole cohort and 1.6%, 1.8%, and 3.5% in the subgroup analysis of R0 resections, respectively. The resection type was not associated with the risk of delayed emptying. Subtotal gastrectomy was associated with a lower risk of major complications and reoperations, whereas distal gastrectomy was associated with a lower risk of anastomotic complications. CONCLUSION: The extent of resection did not affect delayed emptying, whereas fewer postoperative complications were observed after subtotal or distal gastrectomy than after total gastrectomy.

Impact of Primary Tumor Location on Demographics, Resectability, Outcomes, and Quality of Life in Finnish Metastatic Colorectal Cancer Patients (Subgroup Analysis of the RAXO Study).

The primary tumor location (PTL) is associated with the phenotype, metastatic sites, mutations, and outcomes of metastatic colorectal cancer (mCRC) patients, but this has mostly been studied according to sidedness (right vs. left sided). We studied right colon vs. left colon vs. rectal PTL in a real-life study population (n = 1080). Health-related quality of life (HRQoL) was assessed multi-cross-sectionally with QLQ-C30, QLQ-CR29, EQ-5D, and 15D. A chi-square, Kaplan-Meier, and Cox regression were used to compare the groups. The PTL was in the right colon in 310 patients (29%), the left colon in 396 patients (37%), and the rectum in 375 patients (35%). The PTL was associated with distinct differences in metastatic sites during the disease trajectory. The resectability, conversion, and resection rates were lowest in the right colon, followed by the rectum, and were highest in the left colon. Overall survival was shortest for right colon compared with left colon or rectal PTL (median 21 vs. 35 vs. 36 months), with the same trends after metastasectomy or systemic therapy only. PTL also remained statistically significant in a multivariable model. The distribution of symptoms varied according to PTL, especially between the right colon (with general symptoms of metastases) and rectal PTL (with sexual- and bowel-related symptoms). mCRC, according to PTL, behaves differently regarding metastatic sites, resectability of the metastases, outcomes of treatment, and HRQoL.