Mutations In Mismatch Repair Genes Research Articles

Endometrial Carcinomas With Subclonal Loss of Mismatch Repair Proteins: A Clinicopathologic and Genomic Study.

Subclonal loss of mismatch repair (MMR) proteins has been described in a small subset of endometrial carcinomas (ECs), but the genomic basis for this phenomenon has received limited attention. Herein, we retrospectively evaluated all ECs with MMR immunohistochemistry (n=285) for subclonal loss, and in those (n=6), performed a detailed clinicopathologic and genomic comparison of the MMR-deficient and MMR-proficient components. Three tumors were FIGO stage IA, and one each stage IB, II, and IIIC2. Patterns of subclonal loss were as follows: (1) 3 FIGO grade 1 endometrioid carcinomas with subclonal MLH1/PMS2, MLH1 promoter hypermethylation, and no MMR gene mutations; (2) POLE -mutated FIGO grade 3 endometrioid carcinoma with subclonal PMS2, and PMS2 and MSH6 mutations limited to the MMR-deficient component; (3) dedifferentiated carcinoma with subclonal MSH2/MSH6, as well as complete loss of MLH1/PMS2, MLH1 promoter hypermethylation, and PMS2 and MSH6 mutations in both components; (4) dedifferentiated carcinoma with subclonal MSH6, and somatic and germline MSH6 mutations in both components, but with a higher allele frequency in MMR-deficient foci. Recurrences occurred in 2 patients, one consisted of the MMR-proficient component from a FIGO 1 endometrioid carcinoma, while the other was from the MSH6 -mutated dedifferentiated endometrioid carcinoma. At the last follow-up (median: 44mo), 4 patients were alive and disease-free and 2 were alive with disease. In summary, subclonal MMR loss reflects subclonal and often complex genomic and epigenetic alterations, which may have therapeutic implications and therefore must be reported when present. In addition, subclonal loss can occur in both POLE -mutated and Lynch syndrome-associated ECs.

Well-concealed advanced duodenal carcinoma with Muir–Torre syndrome: a case report and review of literature

BackgroundMuir–Torre syndrome is an autosomal-dominant mutation in mismatch repair genes that gives rise to sebaceous tumors and visceral malignancies over time. Because colorectal and genitourinary cancers are common in Muir–Torre syndrome, duodenal carcinoma diagnoses are often delayed.Case presentationA 58-year-old woman presented with severe emaciation, anorexia, and upper abdominal pain. She had a history of rectal carcinoma, ascending colon carcinoma, and a right shoulder sebaceous carcinoma. Upper gastrointestinal endoscopy and computed tomography examinations suggested duodenal obstruction due to superior mesenteric artery syndrome, leading to long-term observation. Seven months later, she was finally diagnosed with duodenal carcinoma of the third portion. As the papilla of Vater was preservable due to tumor location, she received a partial duodenectomy in lieu of a pancreatoduodenectomy. Pathologically, the tumor was a well-differentiated adenocarcinoma with a classification of T3N0M0 Stage IIA (UICC, 8th edition). The postoperative course was uneventful and her appetite returned. A mutation in mismatch repair gene MSH2 confirmed the diagnosis of Muir–Torre syndrome genetically. Three years later, her nutritional status has fully recovered and she is free from both recurrence and metastasis.ConclusionIn patients with comorbid skin sebaceous tumors and gastrointestinal malignancies, genetic screening is strongly recommended. Patients with Muir–Torre syndrome require long-term follow-up, and function-preserving treatment is desirable.

Microsatellite instability (MSI), mismatch repair (MMR), and tumor mutational burden (TMB) as predictive biomarkers for immune checkpoint inhibitor (ICI) effectiveness in real-world patients with metastatic colorectal cancer (mCRC).

46 Background: The KEYNOTE-177 randomized controlled trial demonstrated that mCRC patients with MSI high (MSI-H) and/or deficient MMR (dMMR) have better outcomes on first-line ICI than chemotherapy. This study aimed to evaluate MSI by next-generation sequencing (NGS) as a predictive biomarker of ICI effectiveness in real-world settings, and compare MSI (NGS), dMMR (immunohistochemistry, IHC), and TMB (10 mut/Mb cutoff) in predicting ICI outcomes. Methods: A prospectively declared statistical analysis plan compared the effectiveness of first-line treatment ICI versus chemotherapy in patients with MSI-H mCRC, and compared the predictive power of ICI outcomes associated with biomarkers in any line of therapy (LOT). Patient data was obtained by the US-based de-identified Flatiron Health-Foundation Medicine real-world mCRC clinico-genomic database (FH-FMI CGDB), originating from ~280 US cancer clinics between Jan/2011 and Dec/2021. Differences in progression-free survival (PFS) and overall survival (OS) were evaluated by Cox proportional hazard models, adjusted for a risk score generated from prognostic clinical features. The likelihood ratio test evaluated the superiority of a biomarker in anticipating outcomes. Results: Patients with MSI-H mCRC had more favorable outcomes receiving first-line ICI (n=49) than chemotherapy (n=89) for PFS (median 24.87 vs. 5.65 months, hazard ratio (HR): 0.31, 95% confidence interval (CI) 0.18-0.52, p <0.0001) and OS (median not reached (NR) vs. 24.1 months, HR: 0.45, 95% CI 0.23-0.88, p = 0.02). mCRC patients receiving ICI in any LOT (n=182) had favorable outcomes when MSI-H, dMMR, or TMB ≥10 (all p <0.001). MSI (NGS) and MMR (IHC) were 90% concordant. MSI reclassified six cases that were proficient (p)MMR (all with TMB >10, three with mutations in MMR genes, and 5 with BRAF mutation, consistent with MSI biology). When MSI (NGS) is added to dMMR (IHC) evaluation, there is an improvement in the prediction of TTNT (p = 0.0013), PFS (p = 0.0202), and OS (p = 0.0717), but adding MMR status to MSI did not improve explanatory power. Conclusions: MSI (NGS) robustly identifies mCRC patients with favorable outcomes on first-line ICI vs. chemotherapy, and is a nominally better predictor of ICI outcomes when compared with dMMR (IHC) alone. dMMR (IHC), MSI (NGS), and TMB have similar predictive power for ICI benefit. [Table: see text]

Upper tract urothelial carcinoma in patients with DNA mismatch repair genes mutations. Clinicopathologic characteristics, management, and recurrence patterns

Upper tract urothelial carcinoma in patients with DNA mismatch repair genes mutations. Clinicopathologic characteristics, management, and recurrence patterns

Case report of angiomyofibroblastoma in a patient with lynch syndrome

Lynch syndrome (hereditary non-polyposis colorectal cancer) is a cancer predisposition syndrome caused by mutations in mismatch repair genes. Carcinoma of the colon, endometrium, ovary and urothelium are most common. Soft tissue tumours are not typically associated with Lynch syndrome, however, sarcoma has rarely been reported. We present a case of vulval angiomyofibroblastoma in a patient with known Lynch syndrome. The patient is a 75-year-old female who presented with a vulval lump clinically presumed to be a lipoma.

Gastric neuroendocrine hyperplasia and dysplasia in a patient with Lynch syndrome

Lynch syndrome (LS) is a common hereditary syndrome caused by mutations in deoxyribonucleic acid mismatch repair genes, with a high probability of gastrointestinal, gynaecological and other cancers. The most common LS-associated gastric cancer is adenocarcinoma of the intestinal type. Neuroendocrine neoplasia has not been well understood in LS-associated gastric cancer. Herein, we report a case of a 68-year-old female, with a history of Lynch syndrome and ascending colon adenocarcinoma seven years ago, now presenting as synchronous gastric mixed type adenocarcinoma as well as mucinous adenocarcinoma in transverse colon tumour. On histological examination of the resection specimen, we observe additional diffuse neuroendocrine hyperplasia and dysplasia in the background gastric mucosa. As high grade gastric neuroendocrine carcinoma has been reported in Lynch syndrome, our case may indicate the early stage tumourigenesis of the neuroendocrine tumour in Lynch syndrome.

Muir-Torre Syndrome: A Cutaneous Finding Amidst Broader Malignancies.

Muir-Torre syndrome (MTS) is a rare autosomal dominant genetic condition resulting from microsatellite instability which is caused by mutations in DNA mismatch repair genes. This disorder predisposes individuals to skin tumors and visceral malignancies and may be precipitated in immunocompromised or transplant patients. MTS requires close cancer surveillance for the patient and family because of the tendency to develop aggressive internal malignancies and sebaceous carcinoma. Immunohistochemistry and or genetic testing can confirm the diagnosis of MTS. This review offers an update to the guidelines, diagnosis, and management of MTS while offering a unique perspective on an important but lesser-known syndrome.

Ataxia Telangiectasia Mutated and MSH2 Control Blunt DNA End Joining in Ig Class Switch Recombination.

Class-switch recombination (CSR) produces secondary Ig isotypes and requires activation-induced cytidine deaminase (AID)-dependent DNA deamination of intronic switch regions within the IgH (Igh) gene locus. Noncanonical repair of deaminated DNA by mismatch repair (MMR) or base excision repair (BER) creates DNA breaks that permit recombination between distal switch regions. Ataxia telangiectasia mutated (ATM)-dependent phosphorylation of AID at serine 38 (pS38-AID) promotes its interaction with apurinic/apyrimidinic endonuclease 1 (APE1), a BER protein, suggesting that ATM regulates CSR through BER. However, pS38-AID may also function in MMR during CSR, although the mechanism remains unknown. To examine whether ATM modulates BER- and/or MMR-dependent CSR, Atm-/- mice were bred to mice deficient for the MMR gene mutS homolog 2 (Msh2). Surprisingly, the predicted Mendelian frequencies of Atm-/-Msh2-/- adult mice were not obtained. To generate ATM and MSH2-deficient B cells, Atm was conditionally deleted on an Msh2-/- background using a floxed ATM allele (Atmf) and B cell-specific Cre recombinase expression (CD23-cre) to produce a deleted ATM allele (AtmD). As compared with AtmD/D and Msh2-/- mice and B cells, AtmD/DMsh2-/- mice and B cells display a reduced CSR phenotype. Interestingly, Sμ-Sγ1 junctions from AtmD/DMsh2-/- B cells that were induced to switch to IgG1 in vitro showed a significant loss of blunt end joins and an increase in insertions as compared with wild-type, AtmD/D, or Msh2-/- B cells. These data indicate that the absence of both ATM and MSH2 blocks nonhomologous end joining, leading to inefficient CSR. We propose a model whereby ATM and MSH2 function cooperatively to regulate end joining during CSR through pS38-AID.

Abstract P015: Mechanisms of mitochondrial dysfunction in development of mismatch repair-deficient endometrial cancer

Abstract Background: Lynch syndrome (LS) is a hereditary cancer syndrome carrying roughly 60% lifetime risk of endometrial cancer (EC) development. LS-EC is caused by mutations in mismatch repair genes (most commonly MSH2), which lead to DNA repair deficiency and hypermutability. Identifying mechanisms that impact cancer development could provide novel opportunities for EC prevention. Our recent studies in Msh2-deficient mice identified mitochondrial dysfunction in EC pathogenesis. The objective of this study is to define the impact of MSH2 loss on mitochondrial function and oxidative DNA damage to identify targets for EC prevention. We hypothesized that MSH2 loss disrupts mitochondrial function and increases oxidative DNA damage in EC cells. Methods: The effects of MSH2 loss on EC pathogenesis were evaluated using our novel mouse model for EC development (PR-Cre+Msh2flox/flox, abbreviated Msh2KO) and primary cell lines derived from this model. Mitochondrial stress tests (MSTs) compared mitochondrial function in murine and human MSH2-deficient and -intact EC cell lines. Western blots compared mitochondrial protein expression between cell lines. Transcriptomic data of human ECs from The Cancer Genome Atlas (TCGA) were probed using cBioPortal. To examine direct effects of MSH2 loss on oxidative stress and mitochondrial function, we performed lentiviral shRNA knockdown (KD) of MSH2 in two human EC cell lines (KLE, Hec1a) and MSH2 overexpression (MSH2++) in MFE280 cells. MSTs and Western blots were utilized as above. Immunofluorescent staining compared oxidative DNA damage in MSH2-KD, MSH2++, and control cell lines after pharmacologically induced oxidative stress via H2O2. RESULTS Transcriptomic signatures of histologically normal endometrium and EC from Msh2KO mice versus control mice reveal mitochondrial dysfunction as a key aberrant pathway. MSTs show reduced baseline and induced mitochondrial function in murine and human MSH2-deficient EC cells compared to MSH2-intact (p<0.0001). Western blots show that MSH2-deficient EC cells exhibit loss of mitochondrial complex II compared to MSH2-intact cells (p<0.05). TCGA data confirm MSH2-deficient human ECs have reduced complex II subunits (p<0.05). Isogenic in vitro studies show MSH2-KD reduces complex II expression yet has variable effects on mitochondrial function. MSH2 overexpression increases complex II expression and mitochondrial function. Oxidative DNA damage did not differ at baseline, but H2O2-induced DNA damage increased after MSH2-KD in one of two cell lines. Conclusions: MSH2 and complex II loss are strongly associated in EC. Further studies on the downstream effects of complex II loss are necessary to determine the contribution to LS-EC development. Complex II loss could result in disruptions to oxidative phosphorylation, the citric acid cycle, metabolic reprogramming, and oncometabolite production. Defining direct effects of MSH2 loss on these potential cancer susceptibility mechanisms will open new avenues for LS-associated EC prevention. Citation Format: Diana L. Moreno, Mikayla S. Borthwick, Leah Peralta, Wai Kin Chan, Brenda Melendez, Qian Zhang, Nisha Gokul, Melinda S. Yates. Mechanisms of mitochondrial dysfunction in development of mismatch repair-deficient endometrial cancer. [abstract]. In: Proceedings of the AACR Special Conference: Precision Prevention, Early Detection, and Interception of Cancer; 2022 Nov 17-19; Austin, TX. Philadelphia (PA): AACR; Can Prev Res 2023;16(1 Suppl): Abstract nr P015.

The Largest Chinese Cohort Study Indicates Homologous Recombination Pathway Gene Mutations as Another Major Genetic Risk Factor for Colorectal Cancer with Heterogeneous Clinical Phenotypes.

While genetic factors were associated with over 30% of colorectal cancer (CRC) patients, mutations in CRC-susceptibility genes were identified in only 5% to 10% of these patients. Besides, previous studies on hereditary CRC were largely designed to analyze germline mutations in patients with single genetic high-risk factor, which limited understanding of the association between genotype and phenotypes. From January 2015 to December 2018, we retrospectively enrolled 2,181 patients from 8,270 consecutive CRC cases, covering 5 categories of genetic high-risk factors. Leukocyte genomic DNA was analyzed for germline mutations in cancer predisposition genes. The germline mutations under each category were detected and analyzed in association with CRC susceptibility, clinical phenotypes, and prognoses. A total of 462 pathogenic variants were detected in 19.3% of enrolled CRC patients. Mismatch repair gene mutation was identified in 9.1% of patients, most prevalent across all high-risk groups. Homologous recombination (HR) gene mutations were detected in 6.5% of cases, penetrated in early-onset and extra-colonic cancer risk groups. Mutations in HR genes, including BARD1, RAD50, and ATM, were found to increase CRC risk with odds ratios of 2.8-, 3.1-, and 3.1-fold, respectively. CRC patients with distinct germline mutations manifested heterogeneous phenotypes in clinicopathology and long-term prognoses. Thus, germline mutation screenings should be performed for CRC patients with any of those genetic risk factors. This study also reveals that HR gene mutations may be another major driver for increased CRC risk.

Mismatch repair protein mutations in isocitrate dehydrogenase (IDH)-mutant astrocytoma and IDH-wild-type glioblastoma.

Mutations in mismatch repair (MMR) genes (MSH2, MSH6, MLH1, and PMS2) are associated with microsatellite instability and a hypermutator phenotype in numerous systemic cancers, and germline MMR mutations have been implicated in multi-organ tumor syndromes. In gliomas, MMR mutations can function as an adaptive response to alkylating chemotherapy, although there are well-documented cases of germline and sporadic mutations, with detrimental effects on patient survival. The clinical, pathologic, and molecular features of 18 IDH-mutant astrocytomas and 20 IDH-wild-type glioblastomas with MMR mutations in the primary tumor were analyzed in comparison to 361 IDH-mutant and 906 IDH-wild-type tumors without MMR mutations. In addition, 12 IDH-mutant astrocytomas and 18 IDH-wild-type glioblastomas that developed MMR mutations between initial presentation and tumor recurrence were analyzed in comparison to 50 IDH-mutant and 104 IDH-wild-type cases that remained MMR-wild-type at recurrence. In both IDH-mutant astrocytoma and IDH-wild-type glioblastoma cohorts, the presence of MMR mutation in primary tumors was associated with significantly higher tumor mutation burden (TMB) (P < .0001); however, MMR mutations only resulted in worse overall survival in the IDH-mutant astrocytomas (P = .0069). In addition, gain of MMR mutation between the primary and recurrent surgical specimen occurred more frequently with temozolomide therapy (P = .0073), and resulted in a substantial increase in TMB (P < .0001), higher grade (P = .0119), and worse post-recurrence survival (P = .0022) in the IDH-mutant astrocytoma cohort. These results suggest that whether present initially or in response to therapy, MMR mutations significantly affect TMB but appear to only influence the clinical outcome in IDH-mutant astrocytoma subsets.

Prevalence of mismatch repair genes mutations and clinical activity of PD-1 therapy in Chinese prostate cancer patients.

Prostate cancer (PCa) patients with mismatch repair (MMR) genes mutations are potentially responsive to immune checkpoint blockade (ICB). However, aberrations in MMR genes were rare in PCa and there is evidence that MMR genes mutations are highly ethnic specific. Thus, the prevalence and clinical characteristics of this subgroup in Chinese PCa patients are largely unknown. Furthermore, why some of these patients do not respond to ICB also remains unclear. Here, we analyzed the sequencing data from 3338 Chinese PCa patients to profile the mutation spectrum of the MMR genes. We found that in metastatic disease, the pathogenic mutation frequency of MMR genes in Chinese PCa patients was higher than that in the Caucasus population (4.8 vs 2.2%, P = 0.006) and the mutation carriers responded poorer to androgen deprive therapy (ADT) and abiraterone than non-carriers. Besides, we reported a multi-institutional cases series of 11 PCa patients with mismatch repair deficiency (dMMR) or microsatellite instability high (MSI-H) who received programmed cell death receptor-1 (PD-1) inhibitors, and performed multiplex immunohistochemistry (mIF) to explore the relationship between tumor immune microenvironment (TIME) and response to ICB. The results showed that the responders had higher density of intratumoral CD8+ T cells than non-responders. Our data suggested MMR genes mutations may be more common in Chinese PCa patients, and it is associated with poorer response to hormonal therapies. We propose that the density of intratumoral CD8+ T cells could be a promising predictor to help further subdivide the population of PCa patients who can benefit from immunotherapy.

Exposure of Pseudomonas aeruginosa to Cinnamaldehyde Selects Multidrug Resistant Mutants.

Cinnamaldehyde (CNA), the main component of cinnamon essential oil, is one of the most active plant compounds against nosocomial pathogen Pseudomonas aeruginosa. Exposure of wild-type strain PA14 (MIC 700 µg/mL) for 5 to 10 days to fixed (900 µg/mL) or increasing (from 900 to 1400 µg/mL) concentrations of this natural antibacterial resulted in emergence of resistant mutants CNA-A1 to A3, and CNA-B1 to B7, respectively. Genome sequencing experiments showed that each of CNA-A1 to A3 mutants differed from PA14 by one SNP, and a slight increase in CNA resistance level (from 700 to 900 µg/mL). By comparison, mutants B1 to B7 were more resistant (up to 1100 µg/mL); each of them harbored multiple SNPs (from 24 to 39) likely as a consequence of alteration of DNA mismatch repair gene mutS. Of the ten mutants selected, eight contained mutations in gene nalC, which indirectly downregulates expression of the operon that codes for multidrug efflux system MexAB-OprM, and showed increased resistance (up to 16-fold versus PA14) to antibiotic molecules exported by the pump, including ß-lactams and fluoroquinolones. Of the six mutants with the highest CNA resistance, five were no longer motile because of alteration of genes flgJ, fliE and/or pilJ genes. Altogether, our data show that P. aeruginosa is able to adapt to strong electrophilic molecules such as CNA by upregulating its intrinsic efflux pump MexAB-OprM, and through less well-characterized pleiotropic changes. Whether multidrug-resistant mutants can emerge in patients using cinnamon essential oil as self-medication needs to be assessed further.

The distinct clinical trajectory, metastatic sites, and immunobiology of microsatellite-instability-high cancers.

Microsatellite-instability-high (MSI-H) cancers form a spectrum of solid organ tumors collectively known as Lynch Syndrome cancers, occurring not only in a subset of colorectal, endometrial, small bowel, gastric, pancreatic, and biliary tract cancers but also in prostate, breast, bladder, and thyroid cancers. Patients with Lynch Syndrome harbor germline mutations in mismatch repair genes, with a high degree of genomic instability, leading to somatic hypermutations and, therefore, oncogenesis and cancer progression. MSI-H cancers have unique clinicopathological characteristics compared to their microsatellite-stable (MSS) counterparts, marked by a higher neoantigen load, immune cell infiltration, and a marked clinical response to immune checkpoint blockade. Patients with known Lynch Syndrome may be detected early through surveillance, but some patients present with disseminated metastatic disease. The treatment landscape of MSI-H cancers, especially colorectal cancers, has undergone a paradigm shift and remains to be defined, with immune checkpoint blockade coming to the forefront of treatment strategies in the stage IV setting. We summarize in this review the clinical features of MSI-H cancers with a specific interest in the pattern of spread or recurrence, disease trajectory, and treatment strategies. We also summarize the tumor-immune landscape and genomic profile of MSI-H cancers and potential novel therapeutic strategies.

Loss of mismatch repair promotes a direct selective advantage in human stem cells.

Lynch syndrome (LS) is the most common hereditary form of colon cancer, resulting from a germline mutation in a DNA mismatch repair (MMR) gene. Loss of MMR in cells establishes a mutator phenotype, which may underlie its link to cancer. Acquired downstream mutations that provide the cell a selective advantage would contribute to tumorigenesis. It is unclear, however, whether loss of MMR has other consequences that would directly result in a selective advantage. We found that knockout of the MMR gene MSH2 results in an immediate survival advantage in human stem cells grown under standard cell culture conditions. This advantage results, in part, from an MMR-dependent response to oxidative stress. We also found that loss of MMR gives rise to enhanced formation and growth of human colonic organoids. These results suggest that loss of MMR may affect cells in ways beyond just increasing mutation frequency that could influence tumorigenesis.

Functional characterization of MLH1 missense variants unveils mechanisms of pathogenicity and clarifies role in cancer.

Lynch syndrome is a heritable condition caused by a heterozygous germline inactivating mutation of the DNA mismatch repair (MMR) genes, most commonly the MLH1 gene. However, one third of the identified alterations are missense variants, for which the clinical significance is unclear in many cases. We have identified three MLH1 missense alterations (p.(Glu736Lys), p.(Pro640Thr) and p.(Leu73Pro)) in six individuals from large Tunisian families. For none of these alterations, a classification of pathogenicity was available, consequently diagnosis, predictive testing and targeted surveillance in affected families was impossible. We therefore performed functional laboratory testing using a system testing stability as well as catalytic activity that includes clinically validated reference variants. Both p.(Leu73Pro) and p.(Pro640Thr) were found to be non-functional due to severe defects in protein stability and catalytic activity. In contrast, p.(Glu736Lys) was comparable to the wildtype protein and therefore considered a neutral substitution. Analysis of residue conservation and of the structural roles of the substituted residues corroborated these findings. In conjunction with the available clinical data, two variants fulfil classification criteria for class 4 "likely pathogenic". The findings of this work clarify the mechanism of pathogenicity of two unclear MLH1 variants and enables predictive testing and targeted surveillance in members of carrier families worldwide.

Modeling Therapy-Driven Evolution of Glioblastoma with Patient-Derived Xenografts.

Adult-type diffusely infiltrating gliomas, of which glioblastoma is the most common and aggressive, almost always recur after treatment and are fatal. Improved understanding of therapy-driven tumor evolution and acquired therapy resistance in gliomas is essential for improving patient outcomes, yet the majority of the models currently used in preclinical research are of therapy-naïve tumors. Here, we describe the development of therapy-resistant IDH-wildtype glioblastoma patient-derived xenografts (PDX) through orthotopic engraftment of therapy naïve PDX in athymic nude mice, and repeated in vivo exposure to the therapeutic modalities most often used in treating glioblastoma patients: radiotherapy and temozolomide chemotherapy. Post-temozolomide PDX became enriched for C>T transition mutations, acquired inactivating mutations in DNA mismatch repair genes (especially MSH6), and developed hypermutation. Such post-temozolomide PDX were resistant to additional temozolomide (median survival decrease from 80 days in parental PDX to 42 days in a temozolomide-resistant derivative). However, temozolomide-resistant PDX were sensitive to lomustine (also known as CCNU), a nitrosourea which induces tumor cell apoptosis by a different mechanism than temozolomide. These PDX models mimic changes observed in recurrent GBM in patients, including critical features of therapy-driven tumor evolution. These models can therefore serve as valuable tools for improving our understanding and treatment of recurrent glioma.

"Lynch Syndrome: Current Status of Crc in Biotechnological and Biomedical Fields"

Lynch syndrome (LS) is an autosomal dominant genetic condition caused by mutations in the DNA mismatch repair (MMR) genes in the germline. Colorectal cancer and/or LS-associated cancer are more likely in people who carry pathogenic mutations in these genes. Cancers of the endometrium, small intestine, stomach, pancreas, and biliary tract, ovarian, brain, upper urinary tract, and skin are among the cancer types linked to LS. The criteria for a clinical diagnosis of LS, as well as the processes for genetic testing to identify carriers of pathogenetic mutations in MMR genes, have been known for a long time.

Lobulated red nodule on right lower back.

A 60-year-old man with a history of basal cell carcinoma (BCC) on his forehead excised 10 years ago presented to the dermatology clinic with an enlarging red bump on his back for the past few months. He had no other personal or family history of malignancy and no known radiation exposure (Fig. 1). Physical examination revealed a 2 cm lobulated red nodule with multiple serpiginous vessels coursing through it located on the right lower back. There was no regional lymphadenopathy clinically. Histopathology showed lobules of basaloid tumor cells displaying vesicular, overlapping nuclei, and prominent nucleoli. Admixed aggregates of mature sebocytes, scattered foci of necrosis, and easily identifiable mitotic figures were seen (Fig. 2). Sebaceous carcinoma. This is sebaceous carcinoma, with an estimated incidence of 1–2 cases per 1,000,000 person-years.1, 2 Most cases of sebaceous carcinoma are ocular, and extraocular sites are usually in the head and neck area as a yellowish or red nodule with ulceration.1, 3 Histopathology shows sheets of basaloid and sebaceous cells sheets or asymmetric sebaceous lobules and other signs of malignancy like necrosis, pleomorphism, hyperchromatism, and numerous mitotic figures.1 Mohs surgery is considered first-line for removal of nodules suspicious for sebaceous carcinoma, as is wide-local excision with frozen sections.1 Further studies should include margin assessment of both peripheral and deep tissue edges, with regional lymph node biopsy if there is clinical suspicion of lymphatic involvement.1 As this patient had no clinical lymphadenopathy, no lymph node biopsy was indicated. However, the further pathological analysis showed negative nuclear staining for MSH2 and MSH6, concerning for Muir–Torre syndrome. Muir–Torre syndrome is an autosomal dominant phenotypic variant of Lynch syndrome, and typical findings include a constellation of sebaceous cutaneous neoplasms and visceral malignancies, most commonly colon cancer.4 Immunohistochemistry can be conducted on sebaceous neoplasms to identify mismatch repair gene mutations, and a thorough review of family and personal history of neoplasms as well as personal history of radiation exposure and immunosuppression is indicated. With this patient's multiple sebaceous nodules and DNA mismatch mutation on histology, extensive malignancy workup was started. To date, computed tomography (CT) revealed a multicystic pancreatic tail lesion and multiple metastatic lesions to the liver, with plans to conduct further colonoscopy and upper gastrointestinal (GI) imaging. This case is an excellent example of how dermatologic evaluation can help identify unsuspected internal disease. Sebaceous hyperplasia is incorrect. This is common in older adults and can often be confused with nodular BCC.3 Clinically, these appear as smooth yellow soft umbilicated papules and may elicit sebum with lateral compression, and histopathology would show enlarged sebaceous glands with normal morphology. Typical MCC includes a cutaneous or subcutaneous pink to violet dome-shaped rapidly growing papule or nodule with intact overlying skin in an immunosuppressed patient.3 Histopathology reveals aggregated, deeply blue staining small basaloid or lymphoma-like cells in sheets with CK20 positivity. SCC is incorrect, as these lesions are often plaques or nodules and can be differentiated (hard, keratinized) or undifferentiated (soft, no keratinization).3 These are tumors of pleomorphic keratinocytes that extend into the dermis, and histopathology yields keratinocyte anaplasia, multiple mitoses, and varying degrees of keratinization. FeP is considered a rare variant of BCC characterized by a skin-colored, firm, sessile, fleshy papule, or plaque which often develops in patients with a history of BCC.5 Histopathology is definitive with thin anastomosing basaloid or squamous strands of keratinocytes in a fibrous stroma projecting down from the epidermis, resembling a honeycomb.

Descriptive Statistics for Patients with Glioblastoma Associated with Germline Mismatch Repair Gene Mutation

<h3>Purpose/Objective(s)</h3> Hereditary Nonpolyposis Colorectal Cancer (HNPCC), also known as Lynch Syndrome, is a genetic mismatch repair mutation associated with increased risk for development of glioblastoma (GBM). There is a paucity of data describing the clinical outcomes of GBM patients with HNPCC. We aim to describe tumor characteristics, treatment patterns, and outcomes. <h3>Materials/Methods</h3> IRB approved retrospective review of consecutive patients with a diagnosis of both HNPCC and GBM at a single institution. <h3>Results</h3> Nine patients with a diagnosis of HNPCC and GBM were treated at a single institution from 2001-2022. Six patients were male. Median age at GBM diagnosis was 61 (range 21-84). Median follow up from the time of GBM diagnosis was 7.83 months. Eight patients had prior malignancies: n=7 with colon adenocarcinoma, n=1 with Burkitt lymphoma. Two patients had active synchronous cancers with GBM. The most common presenting symptoms were facial droop (n=3) and cognitive changes (n=2). Others include headache, gait change, visual field defect, and seizures with n=1 each. All patients underwent surgery: n=2 gross total resection, n=4 subtotal resection, and n=3 biopsy alone. There were 3 temporal lobe, 3 parietal lobe, 2 frontal lobe, and 1 frontoparietal lobe tumors. Two patients had multifocal disease at diagnosis. One patient had a giant cell variant GBM. Seven patients had MSH6 mutations and 2 had MSH2 mutations. Two patients progressed rapidly after surgery and were unable to receive RT. Seven patients received adjuvant radiation therapy (RT): n=5 received concurrent TMZ- 1 with concurrent bevacizumab, 5-fluorouracil, and leucovorin due to synchronous metastatic colon cancer, 1 received no chemotherapy. The most common dose and fractionation schedules were 60 Gy in 30 fractions (fx) (n=3), 40.05 Gy in 15 fx (n=3), and n=1 received 30 Gy in 10 fx due to poor performance status and large tumor volume. One patient received proton therapy for active MS, n=8 received IMRT. Two patients initiated tumor treating fields following RT completion. The median time to progression after RT was 3.35 months, and all progressed within the radiation field. Median survival from diagnosis was 6.5 months (range 1.2-15.5). No patients received immune checkpoint inhibitors. One patient was alive at the time of data collection. Seven died due to GBM progression, and n=1 died from progression of a synchronous malignancy. <h3>Conclusion</h3> In this small series, patients with mismatch repair mutation associated glioblastoma had especially poor outcomes and a rapidly progressive disease course.