KIT

KIT (c-KIT / CD117)

一行要約

Type III receptor tyrosine kinase (PDGFR family、4q12 locus)。SCF (stem cell factor) の受容体として造血幹細胞・肥満細胞・ICC (カハール介在細胞)・メラノサイト・胚細胞前駆細胞の分化・生存・遊走を制御する。GIST の 80%+ で activating mutation が driver であり imatinib が paradigm-defining 治療として確立、肥満細胞症では D816V が universal driver で avapritinib が承認。胸腺癌では CD117 IHC 陽性が 80%+ で活性化変異が 5–10%、KIT mutation 陽性例で sunitinib / imatinib が一部活性を示す。NSCLC では KIT mutation は <1% と稀だが SCLC の一部で KIT amplification と発現が報告され、SCF-KIT autocrine loop が SCLC 増殖機序として位置付けられた歴史がある。

主要エビデンス

• GIST: KIT exon 11 (juxtamembrane) mutation が 65–70%、exon 9 (extracellular) が 10%。Imatinib が標準 1L で paradigm-defining。サブグループ間 mutation type による奏効差が確立
• 胸腺癌 (thymic carcinoma) : KIT overexpression (IHC CD117+) 80%+、activating mutation は 5–10% (exon 11 / 17 中心)。基礎 / 臨床的根拠は Yoh et al. LungCancer 2008、症例報告 Strobel et al. NEnglJMed 2004、Palmieri et al. CancerChemotherPharmacol 2012 が Imatinib の臨床活性を提示。Sunitinib (Thomas et al. LancetOncol 2015) / Lenvatinib (Sato et al. LancetOncol 2020) が refractory 胸腺癌で活性を示す。最新 genomic landscape は Mohrmann et al. Med 2025 と Saito et al. Carcinogenesis 2017 が体系化、Imbimbo et al. ESMORareCancers 2025 が現在の treatment algorithm を整理する
• AML: KIT D816V mutation が core-binding factor AML で 20–30%。Avapritinib が開発中
• Mastocytosis: KIT D816V が systemic mastocytosis の universal driver、Avapritinib / Midostaurin が承認
• 肺がん (NSCLC) : KIT mutation は <1% と稀 (Lopez-Chavez et al. JClinOncol 2015 basket trial に含まれる thymic / thoracic 例で標的化検証)。KIT amplification が SCLC の一部で報告、George et al. Nature 2015 でも KIT は recurrent altered RTK のひとつ
• SCLC: 古典的に KIT 高発現が報告され、SCF-KIT autocrine loop が SCLC 増殖の機序として議論されてきた。Sunitinib の SCLC 活性は Leighl et al. JClinOncol 2015 が CALGB 30504 で maintenance setting での PFS benefit を示した (OS benefit は限定的) が、imatinib 単剤は SCLC で臨床的奏効に乏しく、KIT 過剰発現と治療応答性の不一致が SCLC 標的化の長年の課題

メカニズム

KIT 受容体構造:

• 細胞外 (EC) domain D1–D5: Ig-like 領域、D1–D3 が SCF 結合、D4–D5 が dimerization 補助
• 細胞膜貫通 helix
• 細胞内: juxtamembrane (JM, exon 11) → autoinhibitory loop、kinase domain (N-lobe / C-lobe、exon 13–14 が ATP binding、exon 17 に activation loop の D816 残基)
• 統合的 RTK 構造論は Lemmon et al. Cell 2010、Du et al. MolCancer 2018 が体系化

SCF-KIT シグナル伝達:

• SCF (Kit ligand) が KIT EC domain (D1-D3) に結合 → receptor dimerization → activation loop (Y823) の trans-autophosphorylation
• 下流: PI3K-AKT (生存、KIT pY721 経由) / RAS-MAPK (増殖) / JAK-STAT5 (造血幹細胞 self-renewal) / PLCγ (Ca2+ / PKC) / Src family kinase
• JM (juxtamembrane) domain が autoinhibitory loop → activation loop を不活性 conformation に保持。JM mutation でこの autoinhibition が解除され constitutive activation
• Oncogenic kinase signaling 全般のクラス整理は Blume-Jensen et al. Nature 2001

正常細胞での KIT 機能:

• 造血幹細胞 (HSC) : SCF-KIT 軸が long-term self-renewal と早期前駆分化を支える (c-Kit+ Lin- Sca-1+ = LSK 集団の identification にも使用、Weiler et al. Blood 1999)
• Mast cell: SCF が肥満細胞分化・生存・脱顆粒の主要 trophic factor
• ICC (interstitial cells of Cajal) : 消化管 pacemaker 細胞、SCF-KIT 依存性で GIST の origin
• メラノサイト: KIT が melanoblast migration と melanocyte 分化に必須 (piebaldism での loss-of-function 表現型)
• 生殖細胞前駆細胞・innate-like lymphoid cell (c-Kit+ Sca-1+ = ILC2 marker、Moro et al. Nature 2010)

KIT activating mutation の distribution:

• Exon 11 (JM domain) : GIST で最頻 (65–70%)。in-frame deletion / substitution → autoinhibition 解除 → constitutive activation。Imatinib に最も高感受性
• Exon 9 (EC domain, D5) : GIST の 10%、extracellular dimerization 促進。Imatinib 標準量より高用量 (800 mg/日) が必要
• Exon 13/14 (kinase domain) : ATP binding site 近傍。稀 (GIST <5%)
• Exon 17 (activation loop, D816V/H/Y) : 系統的肥満細胞症 / D816V AML / GIST 後天耐性で出現。activation loop の constitutive open conformation を取り、imatinib は結合不能。Avapritinib のみが activation loop selective
• 胸腺癌: KIT mutation の半数以上は exon 11、残りは exon 9 / 17 中心、ただし症例数が限定的

治療標的化 (KIT inhibitor 開発の系譜) :

• Imatinib: type II inhibitor (DFG-out conformation 結合)。exon 11 mutation に高感受性、exon 9 / D816V に低感受性。GIST で paradigm-defining drug
• Sunitinib: multi-kinase inhibitor (KIT + VEGFR + PDGFR)。Imatinib 後 2L (exon 9 / exon 13-14 secondary mutation に活性)。胸腺癌・SCLC でも評価
• Regorafenib: imatinib / sunitinib 耐性 GIST の 3L
• Avapritinib: D816V-selective、activation loop 結合 (type I)。systemic mastocytosis (advanced) で承認、PDGFRA D842V mutation GIST にも承認
• Ripretinib: broad-spectrum KIT/PDGFRA inhibitor、switch pocket binding (type II’)。GIST 4L で承認

Open Questions

• 胸腺癌での KIT 阻害の最適 sequencing: KIT mutation-positive 胸腺癌での Imatinib / Sunitinib / Lenvatinib の選択基準と pretreatment biomarker (Imbimbo et al. ESMORareCancers 2025)
• SCLC の KIT amplification / 高発現の treatment relevance: 古典的に sunitinib maintenance で PFS benefit (Leighl et al. JClinOncol 2015) が示されたが、KIT-specific subset 同定と現代 IO + 化療標準下での再評価
• KIT inhibitor sequential therapy の最適化: GIST で Imatinib → Sunitinib → Regorafenib → Ripretinib の sequencing と avapritinib の合理的位置付け
• Combinatorial resistance: 複数 exon mutation 共存時 (primary + secondary) の治療戦略、polyclonal resistance への対応
• D816V 以外の activation loop mutation: Avapritinib の broader applicability と novel selective inhibitor 開発
• 胸腺癌 IO + KIT inhibitor の rational combination: nivolumab 等 IO と TKI のシナジー (Katsuya et al. FrontOncol 2022) と KIT signaling の immune modulatory 効果
• Liquid biopsy による KIT mutation tracking: ctDNA-based KIT mutation monitoring (Gupta et al. ClinCancerRes 2017 等の方法論的拡張) の standardization

重要論文 Top 10

1. Hirota S et al — Gain-of-function mutations of c-kit in human gastrointestinal stromal tumors — GIST で KIT mutation を driver として同定
2. Demetri GD et al — Efficacy and safety of imatinib mesylate in advanced GIST — Imatinib の GIST 臨床有効性
3. Heinrich MC et al — Kinase mutations and imatinib response in patients with metastatic GIST — KIT mutation type と Imatinib 感受性の相関
4. ★★★★ Thomas et al. LancetOncol 2015 — 胸腺癌での Sunitinib phase II 活性、KIT-positive 胸腺癌の治療標的 paradigm
5. ★★★★ Mohrmann et al. Med 2025 — 胸腺癌の最新 genomic landscape と KIT を含む targeted therapy 統合
6. ★★★★ DeAngelo DJ et al — Avapritinib in advanced systemic mastocytosis (NEJM 2021) — KIT D816V-selective 阻害の臨床実証

関連エンティティ・概念

• EGFR — RTK oncogene addiction の parallel (KIT in GIST = EGFR in NSCLC)
• ALK — TKI sequential therapy の parallel
• PDGFRA — 4q12 locus 近傍、GIST で KIT-wild type の alternative driver

関連論文

直近 30 件のみ表示中 (関連 414 件)。 全件は MOC ページ または Obsidian (source Markdown) から辿れます。

Basic-Brain metastasis

• Wang et al. CancerRes 2026 — VGF-Mediated mitochondrial remodeling fuels lung adenocarcinoma brain metastasis
• Wang et al. IntJBiolSci 2026 — USP33 promotes lung adenocarcinoma brain metastasis by inhibiting the K48-linked ubiquitination and degradation of

Basic-Extracellular vesicles

• Peng et al. CellMolBiolLett 2026 — Lactate-activated astrocytes promote NSCLC brain metastasis through extracellular vesicle-mediated miR-8085trim67elk1
• Chen et al. FrontImmunol 2026 — Exosomal POSTN from cancer-associated fibroblasts drives progression of microinvasive lung adenocarcinoma insights from
• Ma et al. JExtracellVesicles 2026 — Enterococcus faecalis extracellular vesicles deliver the bacterial GTPase obg to hijack mTOR signalling in
• Walther et al. JExtracellVesicles 2026 — Therapeutic poxviruses induce the secretion of immunostimulating and anti-tumoral extracellular vesicles
• Zhang et al. JExtracellVesicles 2026 — In situ engineered cascade-amplified drug-loaded vesicles for enhanced cancer stem cell therapy
• Cai et al. MolCancer 2026 — Extracellular vesicles in solid tumors from tumor ecology to engineered therapeutics
• Tian et al. NatBiomedEng 2026 — Skeletal-muscle-targeted non-viral delivery of full-length DMD mRNA for duchenne muscular dystrophy

Basic-Immunotherapy

• Yue et al. Cell 2026 — Expansion and CAR engineering of granulocyte-monocyte progenitors for cellular immunotherapy
• Jung et al. FrontImmunol 2026 — ATG5-mediated inducible autophagy sustains CAR-T cell durability under solid tumor stress

Basic-Neutrophil and myeloid cell

• Qian et al. Cell 2026 — Respiratory viral infections prime accelerated lung cancer growth
• Pires et al. Immunity 2026 — Innate lymphoid cells activated by the cytokine TL1A link colitis to emergency granulopoiesis and the recruitment of
• Wang et al. NatCancer 2026 — CD300ld on pathologically activated neutrophils promotes tumor immune suppression by binding phosphatidylserine on CD8
• Li et al. NatCommun 2026 — Macrophage-derived fibronectin suppresses antitumor immunity via tissue stiffening and immunosuppressive cell induction

Basic-Oncogene and genetics

• Scaparone et al. CancerDiscov 2026 — EML4-ALK mediates resistance to KRAS G12C inhibition and induces an
• Liu et al. FrontImmunol 2026 — Pan-cancer analysis of OSR2 with a focus on underlying mechanisms and therapeutic implications in lung adenocarcinoma
• Cheek et al. NatGenet 2026 — Age distinguishes selection from causation in cancer genomes

Basic-Others

• Wang et al. Carcinogenesis 2026 — Camrelizumab, apatinib and radiotherapy in locally advanced, unresectable
• Lu et al. NatAging 2026 — Proteomic signatures of the APOE epsilon4 and APOE epsilon2 genetic variants and alzheimer’s disease
• Sarni et al. NatGenet 2026 — A progeria syndrome links DNA hypermethylation to age-related pathology

Basic-Tumor microenvironment

• Skrupskelyte et al. Nature 2026 — Precancerous niche remodelling dictates nascent tumour persistence

Clinical-NSCLC-Driver negative

• Chien et al. CancerImmunolImmunother 2026 — Smoking-associated modulation of gut microbiota shapes response to immune checkpoint inhibitors in non-small cell lun…

Clinical-NSCLC-Driver-Other

• Kropf-Sanchen et al. ClinLungCancer 2026 — A retrospective, multicenter analysis within the national network genomic medicine lung cancer in germany to detect RET
• Zhao et al. LungCancer 2026 — Clinical outcomes and tumor immune microenvironment in SMARCA4-deficient NSCLC A real-world retrospective study

Clinical-NSCLC-EGFR

• Piotrowska et al. CancerDiscov 2026 — ELIOS A multicenter, molecular profiling study of patients with EGFR-mutant advanced non-small cell lung cancer treated

Clinical-Novel modalities

• Kubo et al. BioProtocol 2026 — Cite as kubo, N. et al. (2026). A feeder cell-free system for chimeric antigen receptor gene transduction into

Clinical-Others

• Roulleaux-Dugage et al. JImmunotherCancer 2026 — VEGF-A blockade overcomes liver metastases resistance to chemoimmunotherapy in patients with advanced non-squamous NSCLC

Clinical-Respiratory diseases

• Crawford et al. JCIInsight 2026 — Mesenchyme-derived inflammation during the saccular stage recruits

Clinical-SCLC

• Wang et al. CellRepMed 2026 — Spatial multi-omics unveils the monoclonal origin, neuroendocrine plasticity, and microenvironment niches in combined