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Πέμπτη 30 Μαΐου 2019

Anaplastic lymphoma kinase (ALK) also known as ALK tyrosine kinase receptor or CD246 (cluster of differentiation 246) is an enzyme that in humans is encoded by the ALK gene.ALK plays an important role in the development of the brain and exerts its effects on specific neurons in the nervous system.[6] The deduced amino acid sequences reveal that ALK is a novel receptor tyrosine kinase having a putative transmembrane domain and an extracellular domain. These sequences are absent in the product of the transforming NPM-ALK gene.[7] ALK shows the greatest sequence similarity to LTK (leukocyte tyrosine kinase). Pathology The ALK gene can be oncogenic in three ways – by forming a fusion gene with any of several other genes, by gaining additional gene copies or with mutations of the actual DNA code for the gene itself. Anaplastic large-cell lymphoma The 2;5 chromosomal translocation is associated with approximately 60% anaplastic large-cell lymphomas (ALCLs). The translocation creates a fusion gene consisting of the ALK (anaplastic lymphoma kinase) gene and the nucleophosmin (NPM) gene: the 3' half of ALK, derived from chromosome 2 and coding for the catalytic domain, is fused to the 5' portion of NPM from chromosome 5. The product of the NPM-ALK fusion gene is oncogenic. In a smaller fraction of ALCL patients, the 3' half of ALK is fused to the 5' sequence of TPM3 gene, encoding for tropomyosin 3. In rare cases, ALK is fused to other 5' fusion partners, such as TFG, ATIC, CLTC1, TPM4, MSN, ALO17, MYH9.[8] Adenocarcinoma of the lung The EML4-ALK fusion gene is responsible for approximately 3-5% of non-small-cell lung cancer (NSCLC). The vast majority of cases are adenocarcinomas. The standard test used to detect this gene in tumor samples is fluorescence in situ hybridization (FISH) by a US FDA approved kit. Recently Roche Ventana obtained approval in China and European Union countries to test this mutation by immunohistochemistry.[citation needed] Other techniques like reverse-transcriptase PCR (RT-PCR) can also be used to detect lung cancers with an ALK gene fusion but not recommended.[citation needed] ALK lung cancers are found in patients of all ages, although on average these patients tend to be younger. ALK lung cancers are more common in light cigarette smokers or nonsmokers, but a significant number of patients with this disease are current or former cigarette smokers. EML4-ALK-rearrangement in NSCLC is exclusive and not found in EGFR- or KRAS-mutated tumors.[9] Gene rearrangements and overexpression in other tumours Familial cases of neuroblastoma[10] Inflammatory myofibroblastic tumor[11][12] Adult[13][14] and pediatric[15][16] renal cell carcinomas Esophageal squamous cell carcinoma[17][18] Breast cancer,[19] notably the inflammatory subtype[20] Colonic adenocarcinoma[19] Glioblastoma multiforme[21][22] Anaplastic thyroid cancer[23] ALK inhibitors Main article: ALK inhibitor Xalkori (crizotinib), produced by Pfizer, was approved by the FDA for treatment of late stage lung cancer on August 26, 2011.[24] Early results of an initial Phase I trial with 82 patients with ALK induced lung cancer showed an overall response rate of 57%, a disease control rate at 8 weeks of 87% and progression free survival at 6 months of 72%. Ceritinib was approved by the FDA in April 2014 for the treatment of patients with anaplastic lymphoma kinase (ALK)-positive metastatic non-small cell lung cancer (NSCLC) who have progressed on or are intolerant to crizotinib.[25] Entrectinib (RXDX-101) is a selective tyrosine kinase inhibitor developed by Ignyta, Inc., with specificity, at low nanomolar concentrations, for all of three Trk proteins (encoded by the three NTRK genes, respectively) as well as the ROS1, and ALK receptor tyrosine kinases. An open label, multicenter, global phase 2 clinical trial called STARTRK-2 is currently underway to test the drug in patients with ROS1/NTRK/ALK gene rearrangements.

Biomarkers

Molecular markers used to guide treatment, assess prognosis, or detect relapse.

ALK

In the Phase I/IB study, only patients with NTRK or ROS1 fusions, or an ALK fusion or mutation responded to entrectinib, while patients without these tumor markers didn’t respond.
In the JAMA study, researchers confirmed the previously known clinical and genomic features of NSCLC patients in their large clinico-genomics database.
The draft guidelines have intrigued industry players interested in pursuing labeling that would allow their CDx to direct treatment for a class of drugs instead of one drug.
The assay can identify KRAS, NRAS, PIK3CA, BRAF, and EGFR gene mutations, as well as 19 gene rearrangements of the ALK, ROS1, RET, NTRK1, and MET genes from FFPE.
The agency is excluding certain advanced diagnostic lab tests and molecular pathology tests from a billing regulation that created administrative headaches for many labs.
Patients are organizing themselves in groups based on the molecular features driving their tumors to better advocate for themselves, raise money, and influence research.
The changes include recommendations for first line immunotherapy in patients with high PD-L1 expression, and clarification on use of targeted therapies.
In head-to-head studies, a next-generation EGFR inhibitor and an ALK inhibitor beat their older counterparts in staving of cancer progression.  
The IHC test was used in clinical studies that led to Zykadia's approval last week as a first-line option for metastatic NSCLC patients with ALK rearrangements.
The expanded indication makes it a first-line option for metastatic non-small cell lung cancer patients with ALK rearrangements.

ALK

Using mass spec and small hairpin RNA, they built a map of ALK signaling and identified proteins that could sensitize tumor cells to inhibitor treatment.
Data from the meeting suggest that lung cancer patients with ALK-positive tumors may soon have two first-line options and more choices when their disease progresses.
Repeat molecular analysis of a patient's cancer helped clinicians guide targeted therapies as drug resistance emerged and ebbed.
Genentech's Alecensa and AstraZeneca's Tegrisso are the latest precision lung cancer drugs, and Xalkori might soon be an option for a new molecular subpopulation.
Pfizer's Xalkori yielded significantly longer progression-free survival than standard chemotherapy in the Phase III trial of first-line treatment of ALK-positive NSCLC.

ALK gene

ALK receptor tyrosine kinase

The ALK gene provides instructions for making a protein called ALK receptor tyrosine kinase, which is part of a family of proteins called receptor tyrosine kinases (RTKs). Receptor tyrosine kinases transmit signals from the cell surface into the cell through a process called signal transduction. The process begins when the kinase is stimulated at the cell surface and then attaches to a similar kinase (dimerizes). After dimerization, the kinase is tagged with a marker called a phosphate group (a cluster of oxygen and phosphorus atoms) in a process called phosphorylation. Phosphorylation turns on (activates) the kinase. The activated kinase is able to transfer a phosphate group to another protein inside the cell, which is activated as a result. The activation continues through a series of proteins in a signaling pathway. These signaling pathways are important in many cellular processes such as cell growth and division (proliferation) or maturation (differentiation).
Although the specific function of ALK receptor tyrosine kinase is unknown, it is thought to act early in development to help regulate the proliferation of nerve cells.
At least 16 mutations in the ALK gene have been identified in some people with neuroblastoma, a type of cancerous tumor composed of immature nerve cells (neuroblasts). Neuroblastoma and other cancers occur when a buildup of genetic mutations in critical genes—those that control cell proliferation or differentiation—allows cells to grow and divide uncontrollably to form a tumor. In most cases, these genetic changes are acquired during a person's lifetime and are called somatic mutations. Somatic mutations are present only in certain cells and are not inherited. Less commonly, gene mutations that increase the risk of developing cancer can be inherited from a parent. Both types of mutation occur in neuroblastoma. Somatic mutations in the ALK gene occur during the development of some cases of sporadic neuroblastoma, and inherited mutations in the ALK gene increase the risk of developing familial neuroblastoma.
Mutations in the ALK gene change single protein building blocks (amino acids) in ALK receptor tyrosine kinase. The most common mutation in neuroblastoma replaces the amino acid arginine with the amino acid glutamine at position 1275 (written as Arg1275Gln or R1275Q). Arg1275Gln has been found in both familial and sporadic neuroblastoma and is the only common ALK gene mutation that has been found in both types of the condition.
Occasionally, extra copies of the ALK gene are found in people with neuroblastoma. This phenomenon, known as gene amplification, results in overexpression of ALK receptor tyrosine kinase.
Mutated or overexpressed ALK receptor tyrosine kinase no longer requires stimulation from outside the cell to be phosphorylated. As a result, the kinase and the downstream signaling pathway are constantly turned on (constitutively activated). Constitutive activation of ALK receptor tyrosine kinase may increase the proliferation of immature nerve cells, leading to neuroblastoma.
Genetics Home Reference provides information about lung cancer.
Rearrangements of genetic material involving the ALK gene on chromosome 2 increase the risk of developing several other types of cancer. These rearrangements are somatic mutations, which means they occur during a person's lifetime and are present only in the cells that become cancerous.
One type of rearrangement, called a translocation, exchanges genetic material between chromosome 2 and another chromosome. At least 15 translocations involving the ALK gene have been identified in people with anaplastic large cell lymphoma (ALCL), a rare form of cancer involving immune cells called T cells. The most common translocation in ALCL occurs between chromosome 2 and chromosome 5, called t(2;5). This translocation fuses the ALKgene to the NPM gene and results in a fusion protein called NPM-ALK. In addition, at least seven translocations involving the ALK gene have been identified in inflammatory myofibroblastic tumor (IMT). IMT is a rare cancer characterized by a solid tumor composed of inflammatory cells and cells called myofibroblasts that are important in wound healing. About half of people with IMT have a translocation involving the ALK gene.
Another type of rearrangement, called an inversion, occurs when chromosome 2 is broken in two places and the resulting piece of DNA is reversed and re-inserted into the chromosome. A small group of people with non-small cell lung cancer, the most common type of lung cancer, have an inversion of chromosome 2. This inversion fuses the ALK gene with another gene called EML4 and results in the EML4-ALK fusion protein.
The fusion proteins created by these rearranged genes have functions of both ALK receptor tyrosine kinase and the partner protein. The presence of the partner protein allows phosphorylation of ALK receptor tyrosine kinase without dimerization. The fusion protein and signaling pathways activated by ALK receptor tyrosine kinase are constitutively activated, which may abnormally increase the proliferation of immature nerve cells, leading to cancer formation.
Cytogenetic Location: 2p23.2-p23.1, which is the short (p) arm of chromosome 2 between positions 23.2 and 23.1
Molecular Location: base pairs 29,190,992 to 29,921,611 on chromosome 2 (Homo sapiens Annotation Release 109, GRCh38.p12) (NCBI)
Cytogenetic Location: 2p23.2-p23.1, which is the short (p) arm of chromosome 2 between positions 23.2 and 23.1
  • ALK tyrosine kinase receptor
  • anaplastic lymphoma kinase
  • anaplastic lymphoma receptor tyrosine kinase
  • CD246
  • CD246 antigen
  • NBLST3

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