Mutational Mechanisms That Activate Wnt Signaling and Predict Outcomes in Colorectal Cancer Patients

Serpin peptidase inhibitor, clade E, member 2 in physiology and pathology: recent advancements

Serine protease inhibitors (serpins) are the most numerous and widespread multifunctional protease inhibitor superfamily and are expressed by all eukaryotes. Serpin E2 (serpin peptidase inhibitor, clade E, member 2), a member of the serine protease inhibitor superfamily is a potent endogenous thrombin inhibitor, mainly found in the extracellular matrix and platelets, and expressed in numerous organs and secreted by many cell types. The multiple functions of serpin E2 are mainly mediated through regulating urokinase-type plasminogen activator (uPA, also known as PLAU), tissue-type plasminogen activator (tPA, also known as PLAT), and matrix metalloproteinase activity, and include hemostasis, cell adhesion, and promotion of tumor metastasis. The importance serpin E2 is clear from its involvement in numerous physiological and pathological processes. In this review, we summarize the structural characteristics of the Serpin E2 gene and protein, as well as its roles physiology and disease.

Case report: A colorectal cancer patient with microsatellite instability-high and MSH2 germline mutation failed to respond to anti-PD-1 immunotherapy

Lynch syndrome (LS) is characterized by germline mutations in the DNA mismatch repair (MMR) genes. In colorectal cancer (CRC), germline mutations of DNA MMR genes commonly lead to microsatellite instability-high (MSI-H) subtype formation. Recent studies have demonstrated that CRC patients with MSI-H or mismatch repair-deficient (dMMR) status can benefit from anti-PD1 immunotherapy. However, almost 50% of CRC patients with MSI-H status do not respond to it. It is reported that heterogeneity of tumor and abnormal activation of cancer-related signaling pathways contribute to resistance to anti-PD1 therapy. To improve the clinical efficacy of such patients, the underlying mechanisms of resistance to anti-PD1 treatment must be explored. In this case, we describe an LS-associated CRC patient with MSI-H who suffered resistance to anti-PD1 therapy. Here, we attempted to elucidate the potential reasons, and thus appropriate strategies may be derived to overcome this clinical problem.

Targeted deep sequencing reveals APC mutations as predictors of overall survival in Chinese colorectal patients receiving adjuvant chemotherapy

Objective: Targeted deep sequencing was used to characterize the mutational spectrum of APC in Chinese colorectal tumors in comparison to that in Caucasians from The Cancer Genome Atlas (TCGA) and to investigate whether APC mutations can predict overall survival in CRC patients receiving adjuvant chemotherapy.Methods: A total of 315 Chinese CRC patients including 241 stage II/III patients receiving fluorouracil-based adjuvant chemotherapy were included in this study. Next generation sequencing was carried out to detect somatic mutations on all APC exons. The associations between APC mutations and overall survival were determined by the Cox proportional hazards model.Results:APC was mutated in 221 of 315 colorectal tumors (70.2%). Chinese CRC had a much higher frequency of missense mutations (16.2% vs. 2.4%), but a lower frequency of nonsense (41.0% vs. 54.2%) and frameshift mutations (10.5% vs. 18.4%) than Caucasian CRC. Among stage II/III patients receiving fluorouracil-based adjuvant chemotherapy, APC mutations showed a significant association with worse survival (HR = 1.69; 95% CI, 1.10-2.62; p = .0179). Of the mutation types, frameshift mutations conferred the highest risk of death (HR = 2.88; 95% CI, 1.54-5.37; p =.0009). Among individual mutation sites, Arg232Ter, the most frequent mutation in Chinese CRC, exhibited the strongest negative impact on survival (HR = 2.65; 95% CI, 1.16-6.03; p =.0202).Conclusion:APC overall mutation was an independent predictor for overall survival of stage II/III CRC patients receiving fluorouracil-based chemotherapy.

Regulation of Wnt receptor activity: Implications for therapeutic development in colon cancer

Hyperactivation of Wnt/β-catenin (canonical) signaling in colorectal cancers (CRCs) was identified in the 1990s. Most CRC patients have mutations in genes that encode components of the Wnt pathway. Inactivating mutations in the adenomatous polyposis coli (APC) gene, which encodes a protein necessary for β-catenin degradation, are by far the most prevalent. Other Wnt signaling components are mutated in a smaller proportion of CRCs; these include a FZD-specific ubiquitin E3 ligase known as ring finger protein 43 that removes FZDs from the cell membrane. Our understanding of the genetic and epigenetic landscape of CRC has grown exponentially because of contributions from high-throughput sequencing projects such as The Cancer Genome Atlas. Despite this, no Wnt modulators have been successfully developed for CRC-targeted therapies. In this review, we will focus on the Wnt receptor complex, and speculate on recent discoveries about ring finger protein 43regulating Wnt receptors in CRCs. We then review the current debate on a new APC-Wnt receptor interaction model with therapeutic implications.

Therapeutic Potential of Apatinib Against Colorectal Cancer by Inhibiting VEGFR2-Mediated Angiogenesis and β-Catenin Signaling

Purpose

Apatinib is an inhibitor of VEGFR2 (vascular endothelial growth factor receptor 2) that has attracted a great deal of attention due to its promotion of anticancer activity. In the present study, we investigated the therapeutic effects of apatinib against colorectal cancer (CRC) and examined the underlying mechanism.

Materials and Methods

Both in vivo and in vitro assays were conducted to study the effect of apatinib on CRC. To elucidate the associated mechanism, RNA-seq (transcriptome) analysis was conducted on apatinib-treated HCT116 cells.

Results

Apatinib showed antiproliferative and proapoptotic effects, induced G0/G1 arrest and blocked cell migration and invasion in CRC. An analysis of the mechanism associated with apatinib activity demonstrated that by interacting with VEGFR2, apatinib decreased p-Src, p-Akt, and p-GSK3β levels, which further increased β-catenin ubiquitination and reduced the nuclear translocation of β-catenin. Furthermore, apatinib strongly suppressed CT26 cell growth in mouse xenograft models by inhibiting β-catenin signaling and angiogenesis.

Conclusion

Overall, the results of the present study here indicated that by inhibiting the VEGFR2-β-catenin-mediated malignant phenotype, apatinib significantly suppresses the growth of CRC, suggesting that the use of apatinib is a promising therapeutic strategy for CRC.

Integrative Analysis of Pathological Images and Multi-Dimensional Genomic Data for Early-Stage Cancer Prognosis

The integrative analysis of histopathological images and genomic data has received increasing attention for studying the complex mechanisms of driving cancers. However, most image-genomic studies have been restricted to combining histopathological images with the single modality of genomic data (e.g., mRNA transcription or genetic mutation), and thus neglect the fact that the molecular architecture of cancer is manifested at multiple levels, including genetic, epigenetic, transcriptional, and post-transcriptional events. To address this issue, we propose a novel ordinal multi-modal feature selection (OMMFS) framework that can simultaneously identify important features from both pathological images and multi-modal genomic data (i.e., mRNA transcription, copy number variation, and DNA methylation data) for the prognosis of cancer patients. Our model is based on a generalized sparse canonical correlation analysis framework, by which we also take advantage of the ordinal survival information among different patients for survival outcome prediction. We evaluate our method on three early-stage cancer datasets derived from The Cancer Genome Atlas (TCGA) project, and the experimental results demonstrated that both the selected image and multi-modal genomic markers are strongly correlated with survival enabling effective stratification of patients with distinct survival than the comparing methods, which is often difficult for early-stage cancer patients.

The Hippo and Wnt signalling pathways: crosstalk during neoplastic progression in gastrointestinal tissue

The Hippo and Wnt signalling pathways play crucial roles in maintaining tissue homeostasis and organ size by orchestrating cell proliferation, differentiation and apoptosis. These pathways have been frequently found to be dysregulated in human cancers. While the canonical signal transduction of Hippo and Wnt has been well studied, emerging evidence shows that these two signalling pathways contribute to and exhibit overlapping functions in gastrointestinal (GI) tumorigenesis. In fact, the core effectors YAP/TAZ in Hippo signalling pathway cooperate with β-catenin in Wnt signalling pathway to promote GI neoplasia. Here, we provide a brief review to summarize the molecular mechanisms underlying the crosstalk between these two pathways and elucidate their involvement in GI tumorigenesis, particularly focusing on the intestine, stomach and liver.

Telomere Maintenance-Associated PML Is a Potential Specific Therapeutic Target of Human Colorectal Cancer

Telomere length maintenance is essential for cell proliferation, which is particularly prominent in cancer. We validate that the primary colorectal tumors exhibit heterogeneous telomere lengths but mostly (90%) short telomeres relative to normal tissues. Intriguingly, relatively short telomeres are associated with tumor malignancy as indicated by poorly differentiated state, and these tumors contain more cancer stem-like cells (CSLCs) identified by several commonly used markers CD44, EPHB2 or LGR5. Moreover, promyelocytic leukemia (PML) and ALT-associated PML nuclear bodies (APBs) are frequently found in tumors with short telomeres and high proliferation. In contrast, distant normal tissues rarely or only minimally express PML. Inhibition of PML and APBs by an ATR inhibitor decreases proliferation of CSLCs and organoids, suggesting a potential therapeutic target to progressive colorectal tumors. Together, telomere maintenance underling tumor progression is connected with CSLCs.

Chromatin-associated APC regulates gene expression in collaboration with canonical WNT signaling and AP-1

Mutation of the APC gene occurs in a high percentage of colorectal tumors and is a central event driving tumor initiation in the large intestine. The APC protein performs multiple tumor suppressor functions including negative regulation of the canonical WNT signaling pathway by both cytoplasmic and nuclear mechanisms. Published reports that APC interacts with β-catenin in the chromatin fraction to repress WNT-activated targets have raised the possibility that chromatin-associated APC participates more broadly in mechanisms of transcriptional control. This screening study has used chromatin immunoprecipitation and next-generation sequencing to identify APC-associated genomic regions in colon cancer cell lines. Initial target selection was performed by comparison and statistical analysis of 3,985 genomic regions associated with the APC protein to whole transcriptome sequencing data from APC-deficient and APC-wild-type colon cancer cells, and two types of murine colon adenomas characterized by activated Wnt signaling.

289 transcripts altered in expression following APC loss in human cells were linked to APC-associated genomic regions. High-confidence targets additionally validated in mouse adenomas included 16 increased and 9 decreased in expression following APC loss, indicating that chromatin-associated APC may antagonize canonical WNT signaling at both WNT-activated and WNT-repressed targets. Motif analysis and comparison to ChIP-seq datasets for other transcription factors identified a prevalence of binding sites for the TCF7L2 and AP-1 transcription factors in APC-associated genomic regions. Our results indicate that canonical WNT signaling can collaborate with or antagonize the AP-1 transcription factor to fine-tune the expression of shared target genes in the colorectal epithelium. Future therapeutic strategies for APC-deficient colorectal cancers might be expanded to include agents targeting the AP-1 pathway.