Approximately 35% of colorectal cancer (CRC) risk is attributed to heritable factors, with 5 to 10% linked to dominant or recessive inherited syndromes. Known high-risk genes like POLE, POLD1,... Show moreApproximately 35% of colorectal cancer (CRC) risk is attributed to heritable factors, with 5 to 10% linked to dominant or recessive inherited syndromes. Known high-risk genes like POLE, POLD1, NTHL1 and APC contribute to a portion of this risk. However, the genetic basis for 20%-30% of inherited CRC remains unclear. This thesis explores the roles of POLE, POLD1, APC and NTHL1 in CRC and polyposis. While screening for pathogenic variants in POLE and POLD1, remarkably POLE L424V variants were found to induce Lynch syndrome-like features due to somatic mismatch repair gene mutations. Biallelic NTHL1 variants predisposing to CRC and polyposis were studied in a collaborative effort, describing a broad tumor spectrum and a high risk of extracolonic cancers associated with NTHL1 deficiency. For monoallelic NTHL1 variant carriers, no significant evidence link was found with increased polyposis or CRC risk, as supported by mutational signature analysis on colorectal tumors. Show less
Elsayed, F.A.; Tops, C.M.J.; Nielsen, M.; Morreau, H.; Hes, F.J.; Wezel, T. van 2021
In addition to classic germline APC gene variants, APC mosaicism and deep intronic germline APC variants have also been reported to be causes of adenomatous polyposis. In this study, we... Show moreIn addition to classic germline APC gene variants, APC mosaicism and deep intronic germline APC variants have also been reported to be causes of adenomatous polyposis. In this study, we investigated 80 unexplained colorectal polyposis patients without germline pathogenic variants in known polyposis predisposing genes to detect mosaic and deep intronic APC variants. All patients developed more than 50 colorectal polyps, with adenomas being predominantly observed. To detect APC mosaicism, we performed next-generation sequencing (NGS) in leukocyte DNA. Furthermore, using Sanger sequencing, the cohort was screened for the following previously reported deep intronic pathogenic germline APC variants: c.1408 + 731C > T, p.(Gly471Serfs*55), c.1408 + 735A > T, p.(Gly471Serfs*55), c.1408 + 729A > G, p.(Gly471Serfs*55) and c.532-941G > A, p.(Phe178Argfs*22). We did not detect mosaic or intronic APC variants in the screened unexplained colorectal polyposis patients. The results of this study indicate that the deep intronic APC variants investigated in this study are not a cause of colorectal polyposis in this Dutch population. In addition, NGS did not detect any further mosaic variants in our cohort. Show less
Cameselle-Teijeiro, J.M.; Mete, O.; Asa, S.L.; LiVolsi, V. 2021
Cancer derived from thyroid follicular epithelial cells is common; it represents the most common endocrine malignancy. The molecular features of sporadic tumors have been clarified in the past... Show moreCancer derived from thyroid follicular epithelial cells is common; it represents the most common endocrine malignancy. The molecular features of sporadic tumors have been clarified in the past decade. However the incidence of familial disease has not been emphasized and is often overlooked in routine practice. A careful clinical documentation of family history or familial syndromes that can be associated with thyroid disease can help identify germline susceptibility-driven thyroid neoplasia. In this review, we summarize a large body of information about both syndromic and non-syndromic familial thyroid carcinomas. A significant number of patients with inherited non-medullary thyroid carcinomas manifest disease that appears to be sporadic disease even in some syndromic cases. The cytomorphology of the tumor(s), molecular immunohistochemistry, the findings in the non-tumorous thyroid parenchyma and other associated lesions may provide insight into the underlying syndromic disorder. However, the increasing evidence of familial predisposition to non-syndromic thyroid cancers is raising questions about the importance of genetics and epigenetics. What appears to be "sporadic" is becoming less often truly so and more often an opportunity to identify and understand novel genetic variants that underlie tumorigenesis. Pathologists must be aware of the unusual morphologic features that should prompt germline screening. Therefore, recognition of harbingers of specific germline susceptibility syndromes can assist in providing information to facilitate early detection to prevent aggressive disease. Show less
Aydemirli, M.D.; Tuin, K. van der; Hes, F.J.; Ouweland, A.M.W. van den; Wezel, T. van; Kapiteijn, E.; Morreau, H. 2020
We report a case of a 22-year-old female patient who was diagnosed with a cribriform-morular variant of papillary thyroid carcinoma (CMV-PTC). While at early ages this thyroid cancer variant is... Show moreWe report a case of a 22-year-old female patient who was diagnosed with a cribriform-morular variant of papillary thyroid carcinoma (CMV-PTC). While at early ages this thyroid cancer variant is highly suggestive for familial adenomatous polyposis (FAP), there was no family history of FAP. In the tumor biallelic, inactivating APC variants were identified. The patient tested negative for germline variants based on analysis of genomic DNA from peripheral blood leukocytes. Somatic mosaicism was excluded by subsequent deep sequencing of leukocyte and normal thyroid DNA using next generation sequencing (NGS). This report presents a rare sporadic case of CMV-PTC, and to the best of our knowledge the first featuring two somatic APC mutations underlying the disease, with an overview of CMV-PTC cases with detected APC and CTNNB1 pathogenic variants from the literature. Show less
In view of the complex roles of the canonical Wnt signaling during skeletal devel-opment and disease, it is important to accurately distinguish the specific roles of this signaling cascade at... Show moreIn view of the complex roles of the canonical Wnt signaling during skeletal devel-opment and disease, it is important to accurately distinguish the specific roles of this signaling cascade at specific time windows during embryogenesis as well as postnatally in the maintenance of the skeleton. Moreover, a proper understanding of these multi-faceted roles will ultimately aid us in identifying new therapeutic targets for the treat-ment of growth disorders, osteoporosis and osteoarthritis. Most of the animal models that furnish our knowledge of the effects of canonical Wnt signaling during skeletal development and maintenance use the forced expression of a stabilized and thereby oncogenic _-catenin. The roles of intracellular _-catenin regulators and thereby of wild type _-catenin levels during skeletogenesis, bone mass accrual or AC maintenance are largely unknown. The research described in this thesis aimed at describing the role of two major intracellular regulators of _-catenin, namely Apc and Gsk3_ in regulation of SPC differentiation, bone mass accrual and cartilage maintenance. Show less
In conclusion, this thesis describes several new insights into polyposis, particularly MUTYH-associated polyposis. This recessive inheritable disease represents approximately 10-20% of all... Show moreIn conclusion, this thesis describes several new insights into polyposis, particularly MUTYH-associated polyposis. This recessive inheritable disease represents approximately 10-20% of all polyposis patients with a wide variety in the phenotype and significant genotype-phenotype correlations. Organ systems outside the gastrointestinal tract seem to be relatively spared in MAP patients. Colorectal carcinoma in MAP patients have some specific molecular and histological features, which are similar to MSI-high and Lynch-associated CRCs, such as a preferential proximal location, mucinous histotype, and increased presence of TILs. These TILs could be associated with higher activated immune response, which leads to reduced tumour growth and reduced metastasis. Indeed, better survival in MAP carcinomas was found in a European MAP cohort. Furthermore, it was shown that APC deletion and APC mosaicism represent a substantial number of the discovered APC mutations. The remaining APC and MUTYH negative polyposis patients might have the following: mutations in high penetrance CRC associated genes that are yet to be discovered, mutations in non-scanned parts of the MUTYH or APC genes, or a combination of low penetrance alleles. Show less
Colorectal cancer (CRC) is a complicated disease in which both genetic pre-desposition and environmental factors are important. Patients with inflammatory bowel disease (IBD) have an increased risk... Show moreColorectal cancer (CRC) is a complicated disease in which both genetic pre-desposition and environmental factors are important. Patients with inflammatory bowel disease (IBD) have an increased risk of developing CRC, and it is believed that treatment of IBD patients with 5-Aminosalicylic acid (5-ASA) reduces the CRC risk. The general purpose of the studies described in this thesis was to evaluate the effect of 5-ASA on the development of CRC, as well as determining the feasibility of introducing 5-ASA as an adjuvant therapy for CRC patients. Animal research showed that chronic 5-ASA medication has the ability to prevent colitis-associated CRC, confirming results from 5-ASA medication in IBD patients. Although 5-ASA was not able to prevent the development of sporadic CRC, 5-ASA treatment was found to hold a great promise for the treatment of CRC, by exerting CRC growth inhibiting, anti-progression and cell death inducing effects, and should be considered to be implemented in a future treatment strategy to CRC. Besides this, the determination of cell death products in the circulation of CRC patients and within the tumour, holds a great promise for selection of CRC patient treatment and patient folluw-up. Show less
_-Catenin is an important protein for cancer research as it influences numerous events in the cell that lead to the development of cancer when gone awry. At the adherens junctions, _-catenin... Show more_-Catenin is an important protein for cancer research as it influences numerous events in the cell that lead to the development of cancer when gone awry. At the adherens junctions, _-catenin functions in cell-cell adhesion to maintain epithelial organisation. As an effector of Wnt signaling, _-catenin controls numerous developmental processes as well as homeostatic self-renewal. The effector function of _-catenin is to form a transcriptional complex in the nucleus with TCF/Lef transcription factors to regulate target gene expression. Due to the dual function of _-catenin in cell adhesion and signaling, there are different pools of the protein. The research described in this thesis focuses on the role of _-catenin in the Wnt signaling pathway. What is the pool of _-catenin that is active in signaling? Where is active _-catenin localized? Where and how is _-catenin activated and how is its nuclear export regulated to terminate Wnt signaling. Chapter 1 provides a general introduction about the different aspects of nuclear transport and the Wnt signaling cascade, putting it into the context of cancer development. Chapter 2 describes the identification of Ran-binding protein 3 (RanBP3) as a novel regulator of the active signaling form of _-catenin. We initiated this study to investigate the nuclear translocation of _-catenin and found that RanBP3 directly inhibits _-catenin signaling by stimulating nuclear export of the transcriptionally active form of _-catenin. The active form of _-catenin is unphosphorylated on its N-terminus, and covers only a small fraction of the total amount of _-catenin in the cell. We therefore continued to study the localization of this pool of _-catenin in Chapter 3. We describe that a relative large pool of unphosphorylated _-catenin resides at the adherens junctions, where it most likely functions in cell-cell adhesion. As Wnt treatment induces recruitment of unphosphorylated _-catenin to the plasma membrane, it is impossible to distinguish the resident junctional pool of unphosphorylated _-catenin from the signaling pool. We emphasize the importance of an E-cadherin null background in studying signaling competent unphosphorylated _-catenin. In Chapter 4, we study the unphosphorylated _-catenin pool at the plasma membrane upon Wnt signal induction in E-cadherin knock out cells. Plasma membrane recruitment of _-catenin in the early steps of the Wnt signaling cascade fits with recent new insights, which suggest recruitment of Axin and Dvl to the activated Wnt receptor LRP5/6. We expand these insights by showing that active _-catenin, Axin, APC and activated LRP6 receptor all localize to the plasma membrane upon Wnt stimulation. Moreover, we find that Wnt induced _-catenin is transcriptionally more active than overexpressed _-catenin. We suggest a model in which plasma membrane recruitment of _-catenin represents an important step in _-catenin processing and Wnt signal transduction. In Chapter 5, we determine the nuclear export kinetics of _-catenin in human cells and show that _-catenin exits the nucleus very fast, independently of the CRM1 export pathway and that _-catenin can enhance export of the small molecule GFP (green fluorescent protein). These observations fit into a model in which _-catenin can translocate quickly into and out of the nucleus independently of nuclear transport receptors. Therefore, the activity and localization of _-catenin are likely to be regulated by retention of the protein in the nucleus, cytoplasm and plasma membrane. Finally, in Chapter 6 we reconcile our findings with current knowledge of the Wnt signaling cascade. Show less
