A tumor association to be aware: endometrial cancer and colon cancer in relation to lynch syndrome

lynch syndrome (LS) is an autosomal dominant genetic disorder with incomplete penetration caused by a germline mutation in one of the genes of the deoxyribonucleic acid (DNA) mismatch repair system (MMR) namely: mutL homolog 1 (MLH1), mutS homolog 2 (MSH2), mutS homolog 6 (MHS6), post-meiotic segregation increased 1 homolog 2 (PMS2) or the EpCAM (Epithelial CellAdhesionMolecule) gene, which causes the inactivation of MSH2. Patients with this syndrome have a high relative risk of developing cancers at a young age, led by colorectal cancer (CRC) and endometrial cancer in females. The diagnosis is suspected when the patient’s personal and family history meets the Amsterdam or Bethesda criteria. It is guided by immunohistochemistry (IHC) and/or molecular biology that show loss of expression of one or more proteins of the MMR system and microsatellite instability on tumor DNA. In case of positive IHC and/or molecular biology, the patient should be referred to an oncogenetic consultation for a definitive diagnosis. We present the case of a 49-year-old patient who presented an anaemic syndrome in metrorrhagia. After a clinical, imaging, biological and anatomopathological examination, the diagnosis of LS was made.

Tumor infiltrating lymphocytes (TILs) in endometrioid and clear cell ovarian carcinoma: Characterization, association with mismatch repair system deficiency and endometriosis, and prognostic implications.

e17549 Background: In contrast to high-grade serous ovarian cancer, relationship between tumor infiltrating lymphocytes (TILs) with endometrioid (EC) and clear cell ovarian carcinomas (CC) are less known. However, these tumors are thought to arise from a transformed endometriosis, a disease with a marked inflammatory response, and are also more related to Lynch syndrome. The characterization of TILs in these tumors could lead to stratify patients according to their prognosis and to identify candidates for immumotherapy in case of relapse. Methods: We conducted a retrospective observational study of 121 patients with EC and CC, diagnosed and treated in La Paz University Hospital, from November 1992 until December 2013. An expert pathologist reviewed the histopathological diagnosis, using the immunohistochemical algorithm with WT1, p53, Napsin A and progesterone receptor, and the presence of endometriosis. Clinicopathological data, genetic testing and personal and familial background were collected. Tissue-microarrays (TMAs) were used to analyze CD8+, CD4+ and CD3+ intra-epithelial TILs, according to the score designed by the Ovarian Tumor Tissue Analysis Consortium, peritumoral and endometriosis lymphocytes, ARID1A, MLH1, PMS2, MSH2 and MSH6. Software SPSS18 version was used for descriptive and statistical analysis. Results: Mean age was 54.3 years, and the median follow-up 10.02 years. 48.8% were CC and 51.2% EC, of which, 55.9% were well-differentiated, 32.2% moderately and 11.9% poorly. 58.8% of patients were diagnosed in early stages and 41.2% in advanced ones. 9.1% had family history of ovarian, colorectal or endometrial cancer and 16.5% of breast cancer. 37.2% of patients had a relapse (median progression-free survival of 31 months) and 41.6% died (32.6% related to the tumor). 55.4% of the patients had endometriosis (53.2% were EC and 57.6% CC). 8.2% had lost of MLH1, PMS2, MSH2 or MSH6 and 42% lost ARID1A expression. Moderate or high levels of CD3+, CD8+ and CD4+ TILs were seen in the 57.9%, 53.7% and 1.1%, respectively. There was no relationship between TILs and the lost of MLH1, PMS2, MSH2 and MSH6. Moderate or higher levels of CD3+ TILs were related with better overall survival (OS) only in early stages (p = 0.045). Increased CD8+ TILs in EC patients were associated with a trend towards an improved OS in comparison with those patients with lower or negative CD8+ TILs. Moderate o higher levels of CD8+ TILs were also associated, without statistical significance, with the presence of endometriosis and ARID1A. Conclusions: In our study CD3+ TILs correlated to a better OS, but only in early stages of CC and EC. CD8+ TILs were also associated with a tendency to better OS in EC. We did not find statistically significant association between TILs and Mismatch Repair System deficiency, ARID1A or endometriosis.

Management of Non-Colorectal Digestive Cancers with Microsatellite Instability

Microsatellite instability (MSI) is a hallmark of genetic predisposition to DNA damage. It arises from either germline or somatic events leading to impaired function of the mismatch repair system. It can be detected via genetic sequencing or immunohistochemistry with relatively high concordance rates. The presence of MSI in a tumor reflects a high neoantigen load and predicts favorable treatment response to immune checkpoint inhibitors (ICIs). In gastrointestinal cancers, MSI is a predictive biomarker for ICIs with potential prognostic impact but its clinical utility varies widely depending on tumor type. This may be explained by the complexity of tumor microenvironment as highlighted by recent translational studies. In this review, we will discuss the predictive and prognostic value of MSI status in non-colorectal cancers of the digestive system, important clinical trials involving ICIs and potential strategies to overcome resistance to immunotherapy.

Spatiotemporal manipulation of the mismatch repair system of Pseudomonas putida accelerates phenotype emergence

ABSTRACTDeveloping complex phenotypes in industrially-relevant bacteria is a major goal of metabolic engineering, which encompasses the implementation of both rational and random approaches. In the latter case, several tools have been developed towards increasing mutation frequencies—yet the precise spatiotemporal control of mutagenesis processes continues to represent a significant technical challenge. Pseudomonas species are endowed with one of the most efficient DNA mismatch repair (MMR) systems found in bacteria. Here, we investigated if the endogenous MMR system could be manipulated as a general strategy to artificially alter mutation rates in Pseudomonas species. To bestow a conditional mutator phenotype in the platform bacterium Pseudomonas putida, we constructed inducible mutator devices to modulate the expression of the dominant-negative mutLE36K allele. Regulatable overexpression of mutLE36K in a broad-host-range, easy-to-cure plasmid format resulted in a transitory inhibition of the MMR machinery, leading to a significant increase (up to 438-fold) in mutation frequencies and a heritable fixation of genome mutations. Following such accelerated mutagenesis-followed-by selection approach, three phenotypes were successfully evolved: resistance to antibiotics streptomycin and rifampicin and reversion of a synthetic uracil auxotrophy. Thus, these mutator devices could be applied to accelerate evolution of metabolic pathways in long-term evolutionary experiments, alternating cycles of (inducible) mutagenesis coupled to selection schemes.

Complex Evolution of the Mismatch Repair System in Eukaryotes is Illuminated by Novel Archaeal Genomes

Repairing DNA damage is one of the most important functions of the ‘housekeeping’ proteins, as DNA molecules are constantly subject to different kinds of damage. An important mechanism of DNA repair is the mismatch repair system (MMR). In eukaryotes, it is more complex than it is in bacteria or Archaea due to an inflated number of paralogues produced as a result of an extensive process of gene duplication and further specialization upon the evolution of the first eukaryotes, including an important part of the meiotic machinery. Recently, the discovery and sequencing of Asgard Archaea allowed us to revisit the MMR system evolution with the addition of new data from a group that is closely related to the eukaryotic ancestor. This new analysis provided evidence for a complex evolutionary history of eukaryotic MMR: an archaeal origin for the nuclear MMR system in eukaryotes, with subsequent acquisitions of other MMR systems from organelles.