Molecular Genetic Characteristics of FANCI, a Proposed New Ovarian Cancer Predisposing Gene

FANCI was recently identified as a new candidate ovarian cancer (OC)-predisposing gene from the genetic analysis of carriers of FANCI c.1813C>T; p.L605F in OC families. Here, we aimed to investigate the molecular genetic characteristics of FANCI, as they have not been described in the context of cancer. We first investigated the germline genetic landscape of two sisters with OC from the discovery FANCI c.1813C>T; p.L605F family (F1528) to re-affirm the plausibility of this candidate. As we did not find other conclusive candidates, we then performed a candidate gene approach to identify other candidate variants in genes involved in the FANCI protein interactome in OC families negative for pathogenic variants in BRCA1, BRCA2, BRIP1, RAD51C, RAD51D, and FANCI, which identified four candidate variants. We then investigated FANCI in high-grade serous ovarian carcinoma (HGSC) from FANCI c.1813C>T carriers and found evidence of loss of the wild-type allele in tumour DNA from some of these cases. The somatic genetic landscape of OC tumours from FANCI c.1813C>T carriers was investigated for mutations in selected genes, copy number alterations, and mutational signatures, which determined that the profiles of tumours from carriers were characteristic of features exhibited by HGSC cases. As other OC-predisposing genes such as BRCA1 and BRCA2 are known to increase the risk of other cancers including breast cancer, we investigated the carrier frequency of germline FANCI c.1813C>T in various cancer types and found overall more carriers among cancer cases compared to cancer-free controls (p = 0.007). In these different tumour types, we also identified a spectrum of somatic variants in FANCI that were not restricted to any specific region within the gene. Collectively, these findings expand on the characteristics described for OC cases carrying FANCI c.1813C>T; p.L605F and suggest the possible involvement of FANCI in other cancer types at the germline and/or somatic level.

Practice guidelines for BRCA1/2 tumour testing in ovarian cancer

The purpose of this document is to provide pre-analytical, analytical and post-analytical considerations and recommendations to Canadian clinical laboratories developing, validating and offering next-generation sequencing (NGS)-based BRCA1 and BRCA2 (BRCA1/2) tumour testing in ovarian cancers. This document was drafted by the members of the Canadian College of Medical Geneticists (CCMG) somatic BRCA Ad Hoc Working Group, and representatives from the Canadian Association of Pathologists. The document was circulated to the CCMG members for comment. Following incorporation of feedback, this document has been approved by the CCMG board of directors. The CCMG is a Canadian organisation responsible for certifying medical geneticists and clinical laboratory geneticists, and for establishing professional and ethical standards for clinical genetics services in Canada. The current CCMG Practice Guidelines were developed as a resource for clinical laboratories in Canada; however, they are not inclusive of all information laboratories should consider in the validation and use of NGS for BRCA1/2 tumour testing in ovarian cancers.

A functionally impaired missense variant identified in French Canadian families implicates FANCI as a candidate ovarian cancer-predisposing gene

Background

Familial ovarian cancer (OC) cases not harbouring pathogenic variants in either of the BRCA1 and BRCA2 OC-predisposing genes, which function in homologous recombination (HR) of DNA, could involve pathogenic variants in other DNA repair pathway genes.

Methods

Whole exome sequencing was used to identify rare variants in HR genes in a BRCA1 and BRCA2 pathogenic variant negative OC family of French Canadian (FC) ancestry, a population exhibiting genetic drift. OC cases and cancer-free individuals from FC and non-FC populations were investigated for carrier frequency of FANCI c.1813C>T; p.L605F, the top-ranking candidate. Gene and protein expression were investigated in cancer cell lines and tissue microarrays, respectively.

Results

In FC subjects, c.1813C>T was more common in familial (7.1%, 3/42) than sporadic (1.6%, 7/439) OC cases (P = 0.048). Carriers were detected in 2.5% (74/2950) of cancer-free females though female/male carriers were more likely to have a first-degree relative with OC (121/5249, 2.3%; Spearman correlation = 0.037; P = 0.011), suggesting a role in risk. Many of the cancer-free females had host factors known to reduce risk to OC which could influence cancer risk in this population. There was an increased carrier frequency of FANCI c.1813C>T in BRCA1 and BRCA2 pathogenic variant negative OC families, when including the discovery family, compared to cancer-free females (3/23, 13%; OR = 5.8; 95%CI = 1.7–19; P = 0.005). In non-FC subjects, 10 candidate FANCI variants were identified in 4.1% (21/516) of Australian OC cases negative for pathogenic variants in BRCA1 and BRCA2, including 10 carriers of FANCI c.1813C>T. Candidate variants were significantly more common in familial OC than in sporadic OC (P = 0.04). Localization of FANCD2, part of the FANCI-FANCD2 (ID2) binding complex in the Fanconi anaemia (FA) pathway, to sites of induced DNA damage was severely impeded in cells expressing the p.L605F isoform. This isoform was expressed at a reduced level, destabilized by DNA damaging agent treatment in both HeLa and OC cell lines, and exhibited sensitivity to cisplatin but not to a poly (ADP-ribose) polymerase inhibitor. By tissue microarray analyses, FANCI protein was consistently expressed in fallopian tube epithelial cells and only expressed at low-to-moderate levels in 88% (83/94) of OC samples.

Conclusions

This is the first study to describe candidate OC variants in FANCI, a member of the ID2 complex of the FA DNA repair pathway. Our data suggest that pathogenic FANCI variants may modify OC risk in cancer families.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13073-021-00998-5.

Runx2 association with progression of prostate cancer in patients: mechanisms mediating bone osteolysis and osteoblastic metastatic lesions

Runx2, a bone-specific transcriptional regulator, is abnormally expressed in highly metastatic prostate cancer cells. Here we identified the functional activities of Runx2 in facilitating tumor growth and osteolysis. Our studies demonstrate that negligible Runx2 is found in normal prostate epithelial and non-metastatic LNCaP prostate cancer cells. In the intra-tibial metastasis model, high Runx2 levels are associated with development of large tumors, increased expression of metastasis-related genes (MMP9, MMP13, VEGF, Osteopontin), and secreted bone resorbing factors (PTHrP, IL-8) promoting osteolytic disease. Runx2 siRNA treatment of PC3 cells decreased cell migration and invasion through Matrigel in vitro, and in vivo shRunx2 expression in PC3 cells blocked their ability to survive in the bone microenvironment. Mechanisms of Runx2 function were identified in co-culture studies demonstrating that PC3 cells promote osteoclastogenesis and inhibit osteoblast activity. The clinical significance of these findings is supported by human tissue microarray studies of prostate tumors at stages of cancer progression, where Runx2 is expressed in both adenocarcinomas and metastatic tumors. Together these findings indicate that Runx2 is a key regulator of events associated with prostate cancer metastatic bone disease.

Regulatory role of UvrY in adaptation of Photorhabdus luminescens growth inside the insect

We report global expression profiling of a uvrY-deficient mutant of Photorhabdus luminescens. We found that the regulator moiety of the two-component regulatory system BarA/UvrY regulated more than 500 target genes coding for functions involved in the synthesis of major compartments and metabolic pathways of the cell. This regulation appeared to be in part indirect as UvrY affected the expression of several regulators. Indeed, the flagellum biosynthesis transcription activator FlhC and the flagella regulon were induced in the absence of UvrY, leading to a hyperflagellated phenotype and an increase in motility and biofilm formation. Two major regulatory systems were also altered: the type 2 quorum-sensing inducer AI-2 was activated by UvrY, and the CsrA regulator function appeared to be repressed by the increase of the small-untranslated RNA csrB, the CsrA activity inhibitor TldD and the chaperonin GroESL. Both through and independently of these systems, UvrY regulated oxidative stress resistance; bioluminescence; iron, sugar and peptide transport; proteases; polyketide synthesis enzymes and nucleobases recycling, related to insect degradation and assimilation by bacteria. As a consequence, the uvrY-deficient strain exhibited a decreased killing of insect cells and a reduced growth on insect cells culture, suggesting a UvrY role in the adaptation of P. luminescens inside the insect.

The Long Evans Cinnamon (LEC) rat develops hepatocellular damage in the absence of antimicrosomal antibodies

Long Evans Cinnamon (LEC) rats are an inbred strain with a mutation affecting a copper transporter. As a result, hepatic copper levels rise and the rats spontaneously develop hepatitis that is fatal in about 40% of the rats. The rats that die have been reported to develop anti-microsomal antibodies, most frequently against protein disulfide isomerase (PDI), prior to the onset of liver damage. The association between the presence of antibodies and death of the LEC rats, along with the detection of antibodies prior to the detection of liver damage suggested that the antibodies may have a role in the pathogenesis of liver damage. The objective of this study was to more clearly delineate the temporal relationship between antibody production and the onset of liver damage and copper accumulation. Serum was screened for the presence of anti-microsomal antibodies by immunoblotting. Liver damage was assessed by serum biochemistry and histological examination on rats between 6 and 12 weeks of age (four per group). Copper accumulation in the liver was determined by biochemistry and histological examination. Evidence of liver damage was detectable by serum biochemistry and histopathology by 11.5 weeks. Copper was rarely detected in hepatocytes, although it was detected in macrophages. Sera from only one of seven rats with evidence of liver damage had detectable anti-microsomal protein antibodies. The protein recognized was not PDI. The development of anti-microsomal autoantibodies did not precede the development of significant liver damage, suggesting that they play only a secondary role, if any, in the pathogenesis of hepatitis in this rat strain.

Sequential assessment of an antidrug antibody response in a patient with a systemic delayed-onset sulphonamide hypersensitivity syndrome reaction

A 19-year-old man was treated with trimethoprim-sulphamethoxazole intermittently over 4 weeks. He developed a rash and fever. Despite treatment with low-dose methylprednisolone, his condition worsened. He developed a confluent erythematous macular eruption, elevated liver enzymes, lymphadenopathy, polyserositis and eosinophilia. A tentative diagnosis of sulphonamide hypersensitivity syndrome reaction (SHSR) was made and a serum sample (acute) was obtained to screen for antibodies associated with SHSR. Intravenous methylprednisolone sodium succinate (250 mg every 6 h for 48 h) was administered. The patient's condition improved, and he was discharged with oral prednisone. A convalescent serum sample was obtained 14 weeks later. By Western blotting and enzyme-linked immunosorbent assay (ELISA), antisulphamethoxazole IgG antibodies were detected in the acute serum sample, supporting the clinical diagnosis of SHSR. Contrary to expectations, antibodies were not detected in the convalescent serum sample by immunoblotting. Antisulphamethoxazole antibodies were detected by ELISA in the convalescent serum, but the titre was decreased approximately 45-fold. One possible explanation for the decrease in antibody concentration in the convalescent sample was the administration of high-dose glucocorticoids to the patient following collection of the acute serum sample.