Germline multigene panel testing of patients with endometrial cancer

Endometrial cancer (EC) is the most common gynecological malignancy in developed countries. The present study aimed to determine the frequency of germline pathogenic variants (PV) in patients with EC. In this multicenter retrospective cohort study, germline genetic testing (GGT) was performed in 527 patients with EC using a next generation sequencing panel targeting 226 genes, including 5 Lynch syndrome (LS) and 14 hereditary breast and ovarian cancer (HBOC) predisposition genes, and 207 candidate predisposition genes. Gene-level risks were calculated using 1,662 population-matched controls (PMCs). Patients were sub-categorized to fulfill GGT criteria for LS, HBOC, both or none. A total of 60 patients (11.4%) carried PV in LS (5.1%) and HBOC (6.6%) predisposition genes, including two carriers of double PV. PV in LS genes conferred a significantly higher EC risk [odds ratio (OR), 22.4; 95% CI, 7.8-64.3; P=1.8×10^-17] than the most frequently altered HBOC genes BRCA1 (OR, 3.9; 95% CI, 1.6-9.5; P=0.001), BRCA2 (OR, 7.4; 95% CI, 1.9-28.9; P=0.002) and CHEK2 (OR, 3.2; 95% CI, 1.0-9.9; P=0.04). Furthermore, >6% of patients with EC not fulfilling LS or HBOC GGT indication criteria carried a PV in a clinically relevant gene. Carriers of PV in LS genes had a significantly lower age of EC onset than non-carriers (P=0.01). Another 11.0% of patients carried PV in a candidate gene (the most frequent were FANCA and MUTYH); however, their individual frequencies did not differ from PMCs (except for aggregated frequency of loss-of-function variants in POLE/POLD1; OR, 10.44; 95% CI, 1.1-100.5; P=0.012). The present study demonstrated the importance of GGT in patients with EC. The increased risk of EC of PV carriers in HBOC genes suggests that the diagnosis of EC should be included in the HBOC GGT criteria.

The Spectrum of FANCM Protein Truncating Variants in European Breast Cancer Cases

Germline protein truncating variants (PTVs) in the FANCM gene have been associated with a 2–4-fold increased breast cancer risk in case-control studies conducted in different European populations. However, the distribution and the frequency of FANCM PTVs in Europe have never been investigated. In the present study, we collected the data of 114 European female breast cancer cases with FANCM PTVs ascertained in 20 centers from 13 European countries. We identified 27 different FANCM PTVs. The p.Gln1701* PTV is the most common PTV in Northern Europe with a maximum frequency in Finland and a lower relative frequency in Southern Europe. On the contrary, p.Arg1931* seems to be the most common PTV in Southern Europe. We also showed that p.Arg658*, the third most common PTV, is more frequent in Central Europe, and p.Gln498Thrfs*7 is probably a founder variant from Lithuania. Of the 23 rare or unique FANCM PTVs, 15 have not been previously reported. We provide here the initial spectrum of FANCM PTVs in European breast cancer cases.

The human transient receptor potential vanilloid 3 channel is sensitized via the ERK pathway

The transient receptor potential vanilloid 3 (TRPV3) channel is a Ca²⁺-permeable thermosensitive ion channel widely expressed in keratinocytes, where together with epidermal growth factor receptor (EGFR) forms a signaling complex regulating epidermal homeostasis. Proper signaling through this complex is achieved and maintained via several pathways in which TRPV3 activation is absolutely required. Results of recent studies have suggested that low-level constitutive activity of TRPV3 induces EGFR-dependent signaling that, in turn, amplifies TRPV3 via activation of the mitogen-activated protein kinase ERK in a positive feedback loop. Here, we explored the molecular mechanism that increases TRPV3 activity through EGFR activation. We used mutagenesis and whole-cell patch clamp experiments on TRPV3 channels endogenously expressed in an immortalized human keratinocyte cell line (HaCaT) and in transiently transfected HEK293T cells and found that the sensitizing effect of EGFR on TRPV3 is mediated by ERK. We observed that ERK-mediated phosphorylation of TRPV3 alters its responsiveness to repeated chemical stimuli. Among several putative ERK phosphorylation sites, we identified threonine 264 in the N-terminal ankyrin repeat domain as the most critical site for the ERK-dependent modulation of TRPV3 channel activity. Of note, Thr²⁶⁴ is in close vicinity to a structurally and functionally important TRPV3 region comprising an atypical finger 3 and oxygen-dependent hydroxylation site. In summary, our findings indicate that Thr²⁶⁴ in TRPV3 is a key ERK phosphorylation site mediating EGFR-induced sensitization of the channel to stimulate signaling pathways involved in regulating skin homeostasis.

Gain-of-function mutations in the transient receptor potential channels TRPV1 and TRPA1: how painful?

Gain-of-function (GOF) mutations in ion channels are rare events, which lead to increased agonist sensitivity or altered gating properties, and may render the channel constitutively active. Uncovering and following characterization of such mutants contribute substantially to the understanding of the molecular basis of ion channel functioning. Here we give an overview of some GOF mutants in polymodal ion channels specifically involved in transduction of painful stimuli--TRPV1 and TRPA1, which are scrutinized by scientists due to their important role in development of some pathological pain states. Remarkably, a substitution of single amino acid in the S4-S5 region of TRPA1 (N855S) has been recently associated with familial episodic pain syndrome. This mutation increases chemical sensitivity of TRPA1, but leaves the voltage sensitivity unchanged. On the other hand, mutations in the analogous region of TRPV1 (R557K and G563S) severely affect all aspects of channel activation and lead to spontaneous activity. Comparison of the effects induced by mutations in homologous positions in different TRP receptors (or more generally in other distantly related ion channels) may elucidate the gating mechanisms conserved during evolution.