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The phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (the HUGO-approved official symbol = PIK3CA; HGNC ID, HGNC:8975), also called p110α protein, is a class I PI 3-kinase catalytic subunit. The human p110α protein is encoded by the PIK3CA gene. [5]
Its role was uncovered by molecular pathological epidemiology (MPE). [6]
Phosphatidylinositol-4,5-bisphosphate 3-kinase (also called phosphatidylinositol 3-kinase (PI3K)) is composed of an 85 kDa regulatory subunit and a 110 kDa catalytic subunit. The protein encoded by this gene represents the catalytic subunit, which uses ATP to phosphorylate phosphatidylinositols (PtdIns), PtdIns4P and PtdIns(4,5)P2. [7]
The involvement of p110α in human cancer has been hypothesized since 1995. Support for this hypothesis came from genetic and functional studies, including the discovery of common activating PIK3CA missense mutations in common human tumors. [8] It has been found to be oncogenic and is implicated in cervical cancers. [9] PIK3CA mutations are present in over one-third of breast cancers, with enrichment in the luminal and in human epidermal growth factor receptor 2-positive subtypes (HER2 +). The three hotspot mutation positions (GLU542, GLU545, and HIS1047) have been widely reported till date. [10] While substantial preclinical data show an association with robust activation of the pathway and resistance to common therapies, clinical data do not indicate that such mutations are associated with high levels of pathway activation or with a poor prognosis. It is unknown whether the mutation predicts increased sensitivity to agents targeting the P3K pathway. [11]
PIK3CA participates in a complex interaction within the tumor microenvironment in this phenomenon. [12]
Due to the association between p110α and cancer, [13] it may be an appropriate drug target. Pharmaceutical companies are designing and characterizing potential p110α isoform specific inhibitors. [14] [15]
The presence of [a] PIK3CA mutation may predict response to aspirin therapy for colorectal cancer. [16] [17]
Somatic activating mutations in PIK3CA are found in Klippel–Trénaunay syndrome and venous malformation. [18] [19]
PIK3CA-associated segmental overgrowth includes brain disorders such as macrocephaly-capillary malformation (MCAP) and hemimegalencephaly. It is also associated with congenital, lipomatous overgrowth of vascular malformations, epidermal nevi and skeletal/spinal anomalies (CLOVES syndrome) and fibroadipose hyperplasia (FH). The conditions are caused by heterozygous (usually somatic mosaic) mutations. [20]
All PI 3-kinases are inhibited by the drugs wortmannin and LY294002 but wortmannin shows better efficiency than LY294002 on the hotspot mutation positions. [21] [22]
In September 2017 Copanlisib, inhibiting predominantly p110α and p110δ, got FDA approval for the treatment of adult patients with relapsed follicular lymphoma (FL) who have received at least two prior systemic therapies. [23]
P110α has been shown to interact with:
In biochemistry, a kinase is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the high-energy ATP molecule donates a phosphate group to the substrate molecule. This transesterification produces a phosphorylated substrate and ADP. Conversely, it is referred to as dephosphorylation when the phosphorylated substrate donates a phosphate group and ADP gains a phosphate group. These two processes, phosphorylation and dephosphorylation, occur four times during glycolysis.
Wortmannin, a steroid metabolite of the fungi Penicillium funiculosum, Talaromyces wortmannii, is a non-specific, covalent inhibitor of phosphoinositide 3-kinases (PI3Ks). It has an in vitro inhibitory concentration (IC50) of around 5 nM, making it a more potent inhibitor than LY294002, another commonly used PI3K inhibitor. It displays a similar potency in vitro for the class I, II, and III PI3K members although it can also inhibit other PI3K-related enzymes such as mTOR, DNA-PKcs, some phosphatidylinositol 4-kinases, myosin light chain kinase (MLCK) and mitogen-activated protein kinase (MAPK) at high concentrations Wortmannin has also been reported to inhibit members of the polo-like kinase family with IC50 in the same range as for PI3K. The half-life of wortmannin in tissue culture is about 10 minutes due to the presence of the highly reactive C20 carbon that is also responsible for its ability to covalently inactivate PI3K. Wortmannin is a commonly used cell biology reagent that has been used previously in research to inhibit DNA repair, receptor-mediated endocytosis and cell proliferation.
Protein kinase B (PKB), also known as Akt, is the collective name of a set of three serine/threonine-specific protein kinases that play key roles in multiple cellular processes such as glucose metabolism, apoptosis, cell proliferation, transcription, and cell migration.
ATM serine/threonine kinase or Ataxia-telangiectasia mutated, symbol ATM, is a serine/threonine protein kinase that is recruited and activated by DNA double-strand breaks, oxidative stress, topoisomerase cleavage complexes, splicing intermediates, R-loops and in some cases by single-strand DNA breaks. It phosphorylates several key proteins that initiate activation of the DNA damage checkpoint, leading to cell cycle arrest, DNA repair or apoptosis. Several of these targets, including p53, CHK2, BRCA1, NBS1 and H2AX are tumor suppressors.
Phosphoinositide 3-kinases (PI3Ks), also called phosphatidylinositol 3-kinases, are a family of enzymes involved in cellular functions such as cell growth, proliferation, differentiation, motility, survival and intracellular trafficking, which in turn are involved in cancer.
Class I PI 3-kinases are a subgroup of the enzyme family, phosphoinositide 3-kinase that possess a common protein domain structure, substrate specificity, and method of activation. Class I PI 3-kinases are further divided into two subclasses, class IA PI 3-kinases and class IB PI 3-kinases.
Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta isoform also known as phosphoinositide 3-kinase (PI3K) delta isoform or p110δ is an enzyme that in humans is encoded by the PIK3CD gene.
Phosphatidylinositol 3-kinase regulatory subunit alpha is an enzyme that in humans is encoded by the PIK3R1 gene.
DNA-dependent protein kinase, catalytic subunit, also known as DNA-PKcs, is an enzyme that in humans is encoded by the gene designated as PRKDC or XRCC7. DNA-PKcs belongs to the phosphatidylinositol 3-kinase-related kinase protein family. The DNA-Pkcs protein is a serine/threonine protein kinase consisting of a single polypeptide chain of 4,128 amino acids.
Phosphatidylinositol 3-kinase regulatory subunit beta is an enzyme that in humans is encoded by the PIK3R2 gene.
Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit gamma isoform is an enzyme that in humans is encoded by the PIK3CG gene.
Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit beta isoform is an enzyme that in humans is encoded by the PIK3CB gene.
Phosphatidylinositol-4-phosphate 3-kinase C2 domain-containing beta polypeptide is an enzyme that in humans is encoded by the PIK3C2B gene.
LY294002 is a morpholine-containing chemical compound that is a potent inhibitor of numerous proteins, and a strong inhibitor of phosphoinositide 3-kinases (PI3Ks). It is generally considered a non-selective research tool, and should not be used for experiments aiming to target PI3K uniquely.
The Akt signaling pathway or PI3K-Akt signaling pathway is a signal transduction pathway that promotes survival and growth in response to extracellular signals. Key proteins involved are PI3K and Akt.
Lewis C. Cantley is an American cell biologist and biochemist who has made significant advances to the understanding of cancer metabolism. Among his most notable contributions are the discovery and study of the enzyme PI-3-kinase, now known to be important to understanding cancer and diabetes mellitus. He is currently Meyer Director and Professor of Cancer Biology at the Sandra and Edward Meyer Cancer Center at Weill Cornell Medicine in New York City. He was formerly a professor in the Departments of Systems Biology and Medicine at Harvard Medical School, and the Director of Cancer Research at the Beth Israel Deaconess Medical Center, in Boston, Massachusetts. In 2016, he was elected Chairman of the Board for the Hope Funds for Cancer Research.
CLOVES syndrome is a rare overgrowth syndrome with complex vascular anomalies. CLOVES syndrome affects people with various symptoms, ranging from mild fatty soft-tissue tumors to vascular malformations encompassing the spine or internal organs.
Gedatolisib (PF-05212384) is an experimental drug for treatment of cancer in development by Celcuity, Inc. The mechanism of action is accomplished by binding the different p110 catalytic subunit isoforms of PI3K and the kinase site of mTOR.
PIK3CA-related overgrowth spectrum (PROS) is an umbrella term for rare syndromes characterized by malformations and tissue overgrowth caused by somatic mutations in PIK3CA gene. In PROS diseases individuals malformations are seen in several different tissues such as skin, vasculature, bones, fat and brain tissue depending on the specific disease.
Inavolisib, or GDC-0077, is an early-phase, highly selective inhibitor and degrader of mutant phosphatidylinositol 3-kinase (PI3K) alpha. The PI3K-mediated signalling pathway has shown to play an important role in the development of tumours as dysregulation is commonly associated with tumour growth and resistance to antineoplastic agents and radiotherapy.
