A familial germline mutation in KIT associated with achalasia, mastocytosis and gastrointestinal stromal tumors shows response to kinase inhibitors

Therapeutic modulation of KIT ligand in melanocytic disorders with implications for mast cell diseases

KIT ligand and its associated receptor KIT serve as a master regulatory system for both melanocytes and mast cells controlling survival, migration, proliferation and activation. Blockade of this pathway results in cell depletion, while overactivation leads to mastocytosis or melanoma. Expression defects are associated with pigmentary and mast cell disorders. KIT ligand regulation is complex but efficient targeting of this system would be of significant benefit to those suffering from melanocytic or mast cell disorders. Herein, we review the known associations of this pathway with cutaneous diseases and the regulators of this system both in skin and in the more well-studied germ cell system. Exogenous agents modulating this pathway will also be presented. Ultimately, we will review potential therapeutic opportunities to help our patients with melanocytic and mast cell disease processes potentially including vitiligo, hair greying, melasma, urticaria, mastocytosis and melanoma.

Whole-exome sequencing reveals common and rare variants in immunologic and neurological genes implicated in achalasia

Idiopathic achalasia (IA) is a severe motility disorder characterized by neuronal degeneration in the myenteric plexus, but the etiology remains largely unknown. We performed whole-exome sequencing (WES) in 100 IA-affected individuals and 313 non-IA control subjects and validated the results in 230 IA-affected individuals and 1,760 non-IA control subjects. Common missense variants rs1705003 (CUTA, GenBank: NC_000006.11:g.33385953A>G) and rs1126511 (HLA-DPB1, GenBank: NC_000006.11:g.33048466G>T) at 6p21.32 were reproducibly associated with increased risk of IA (rs1126511: OR = 1.83, p = 2.34 × 10^-9; rs1705003: OR = 2.37, p = 3.21 × 10^-7), meeting exome-wide significance. Both variants can affect the expression of their target genes at the transcript level. An array-based association analysis in 280 affected individuals and 1,121 control subjects determined the same signal at 6p21.32. Further conditional analyses supported that the two missense variants identified in WES-based association study were potential causal variants of IA. For rare variants, the top genes identified by gene-based analysis were significantly enriched in nerve and muscle phenotypic genes in the mouse. Moreover, the functional rare variants in these genes tended to cooccur in IA-affected individuals. In an independent cohort, we successfully validated three rare variants (CREB5, GenBank: NC_000007.13:g.28848865G>T; ESYT3, GenBank: NC_000003.11:g.138183253C>T; and LPIN1, GenBank: NC_000002.11:g.11925128A>G) which heightens the risk of developing IA. Our study identified and validated two common variants and three rare variants associated with IA in immunologic and neurological genes, providing new insight into the etiology of IA.

The Mechanisms for the Association of Cancer and Esophageal Dysmotility Disorders

BACKGROUND

Achalasia and other esophageal dysmotility disorders mimicking achalasia can be associated with cancer. This study aimed to review the main mechanisms for which cancer may develop in esophageal dysmotility disorder patients.

METHODS

A narrative review was performed.

RESULTS

The mechanism for developing squamous cell carcinoma and adenocarcinoma are discussed. Besides, achalasia-like syndromes related to familial KIT-gene mutation and pseudoachalasia are discussed.

CONCLUSIONS

Knowing the main mechanism for which achalasia can be related to cancer is essential for clinicians to conduct the proper investigation, surveillance, and treatment.

[The significance of C-KIT gene mutations in the diagnosis and prognosis of malignant tumors]

Mutations in the C-KIT gene encoding type III receptor tyrosine kinase that regulates cellular processes, such as differentiation, survival, proliferation, migration, and apoptosis, are found in some neoplasms: gastrointestinal stromal tumor, mastocytosis, melanoma, breast carcinomas, myeloid leukemias, and a number of others. Tumors that exhibit these mutations are sensitive to therapy with tyrosine kinase inhibitors, which makes it necessary to correctly identify the mutation status by C-KIT in order to apply a personalized approach to therapy. This literature review shows that the type and localization of the C-KIT gene mutation are of crucial prognostic value and significance in choosing drugs for antitumor therapy, but traditional diagnostic methods fail to determine accurate mutation characteristics. Routine sequencing techniques focus on identifying the gene mutations associated with specific cellular processes, such as DNA damage and repair. The emergence of next-generation sequencing techniques has solved this problem, making it possible to fully analyze the genome of a malignant neoplasm, with constant screening for new mutations that appear as the tumor develops, affect the prognosis of the disease, and change its sensitivity to the antitumor therapy.

A Novel Kindred with Familial Gastrointestinal Stromal Tumors Caused by a Rare KIT Germline Mutation (N655K): Clinico-Pathological Presentation and TKI Sensitivity

Gastrointestinal stromal tumors (GISTs), the most common mesenchymal tumors of the gastrointestinal tract, are characterized by activating mutations in KIT or PDGFRA genes. The vast majority of GISTs are sporadic, but rare hereditary forms have been reported, often featuring multifocality and younger age of onset. We here report the identification of a novel kindred affected by familial GIST caused by a KIT germline mutation in exon 13 (N655K). No family affected by hereditary GIST due to this KIT variant has been reported in literature so far. We were able to track the mutation in three members of the family (proband, mother, and second-degree cousin), all affected by multiple GISTs. Due to its rarity, the N655K variant is poorly characterized. We conducted in vitro drug sensitivity assays that indicated that most tyrosine kinase inhibitors (TKIs) currently included in the therapeutic armamentarium for GISTs have a limited inhibitory activity toward this mutation. However, when compared to a classical imatinib-resistant KIT mutation (T670I), N655K was slightly more sensitive to imatinib, and encouraging responses were observed with last-generation TKIs.