Molecular Mechanism and Targeted Therapy

The Laboratory of Cancer Signalling was founded in November 2014. The laboratory focuses on understanding how aberrant protein kinase signaling drives tumorigenesis and on developing effective targeted therapies for cancer.

First, the laboratory investigates the molecular mechanisms regulating the RAF/MEK/ERK kinase cascade and develops next-generation inhibitors targeting this pathway. Using Spine-based mutagenesis, the laboratory elucidated the mechanisms underlying dimerization-driven transactivation of RAF kinases (Hu et al., PNAS, 2011; Hu et al., Cell, 2013; Hu et al., MCB, 2015; Yuan et al., Oncogene, 2018). By Characterising oncogenic RAF and MEK mutants with β3–αC loop deletions, the laboratory further revealed a dimer-to-dimer mechanism of signal transduction, in which RAF/RAF, RAF/MEK, and MEK/MEK interactions are essential for pathway activation. These findings provide the basis for developing next-generation RAF and MEK inhibitors that target critical protein–protein interactions within the kinase cascade for RTK/RAS/RAF-mutated cancers.

Second, the laboratory investigates mechanisms of resistance to RAF-targeted therapies and develops strategies to overcome them. Although RAF inhibitors can produce initial clinical responses, resistance frequently emerges through RTK/RAS alterations or aberrant BRAF(V600E) splicing. AMPK was identified as a potential target for overcoming RTK/RAS-mediated resistance (Yuan et al., JBC, 2018), while genome-wide screening is underway to identify targets for aberrant BRAF(V600E) splicing. Mechanistic studies further demonstrated that stabilisation of the RAF Regulatory Spine is a fundamental determinant of drug resistance (Yap et al., Science Advances, 2021). In addition, the mechanisms by which non-V600 BRAF mutations evade regulation by the Cdc37/Hsp90 chaperone and 14-3-3 scaffold were elucidated, enabling the development of a precision therapeutic strategy for these mutations (Wan et al., Theranostics, 2025).

Finally, the laboratory develops genetic mouse models to investigate cancer pathogenesis and evaluate novel therapies. A BRAF(V600E)-driven hairy cell leukemia model was established to investigate disease mechanisms and develop therapeutic strategies (Yap et al., Molecular Cancer, 2023). Additional models of BRAF(V600E)-driven histiocytosis and Kras(G12D)-driven hepatocellular carcinoma are under development, providing platforms to study tumour pathogenesis, therapeutic responses, host immune interactions, and potential drug combinations.

Overall, the research integrates fundamental kinase biology, mechanisms of therapeutic resistance, drug development, and genetically engineered cancer models to advance targeted therapies for RTK/RAS/RAF-driven cancers.

Figure 1: Hyperactivation of Ras/Raf/MEK/ERK signalling in cancers. Abbreviations: EGFR, epidermal growth factor receptor; HER2, human epidermal receptor-2; MEK, mitogen-activated protein kinase kinase; MAPK, mitogen-actived protein kinase; NSCLC, non-small cell lung cancer; RTK, receptor tyosine kinase; SB/LGS, serous borderline/low-grade serous.

Selected publications:

1. Li Q, Hu J: Langerhans cell histiocytosis: molecular mechanisms underlying pathogenesis and emerging targeted therapeutics. Cancer Metastasis Rev 2026 (In Press) 
2. Zhang G, Hu J: Hairy cell leukemia: a chronic B-cell lymphoma with unique clinicopathological features and unresolved molecular mechanisms. Blood Adv 2026, 10:1012-1022. 
3. Wan X, Yap J, Chen J, Li Y, Faruk R, Tan NCB, Ma Y, Lim Y, Jubri KB, Hu JY, Yan J, Zhang G, Li Q, Yap YS, Lam P, Wang M, Fu NY,  Hu J: Oncogenic non-V600 mutations evade the regulatory machinery of RAF including the Cdc37/Hsp90 chaperone and the 14-3-3 scaffold. Theranostics 2025, 15:2035-2051. 
4. Yap J, Yuan J, Ng WH, Chen GB, Sim YRM, Goh KC, Teo J, Lim TYH, Goay SM, Teo JHJ, Lao Z, Lam P, Sabapathy K, Hu J: BRAF(V600E) mutation together with loss of Trp53 or pTEN drives the origination of hairy cell leukemia from B-lymphocytes. Mol Cancer 2023, 22:125. 
5. Yap J, Deepak R, Tian Z, Ng WH, Goh KC, Foo A, Tee ZH, Mohanam MP, Sim YRM, Degirmenci U, Lam P, Chen Z, Fan H, Hu J: The stability of R-spine defines RAF inhibitor resistance: A comprehensive analysis of oncogenic BRAF mutants with in-frame insertion of alphaC-beta4 loop. Sci Adv 2021, 7. 
6. Degirmenci U, Yap J, Sim YRM, Qin S, Hu J: Drug resistance in targeted cancer therapies with RAF inhibitors. Cancer Drug Resist 2021, 4:665-683. 
7. Degirmenci U, Wang M, Hu J: Targeting Aberrant RAS/RAF/MEK/ERK Signaling for Cancer Therapy. Cells 2020, 9. 
8. Yuan J, Ng WH, Tian Z, Yap J, Baccarini M, Chen Z, Hu J: Activating mutations in MEK1 enhance homodimerization and promote tumorigenesis. Sci Signal 2018, 11. 
9. Yuan J, Ng WH, Lam PYP, Wang Y, Xia H, Yap J, Guan SP, Lee ASG, Wang M, Baccarini M, Hu J: The dimer-dependent catalytic activity of RAF family kinases is revealed through characterizing their oncogenic mutants. Oncogene 2018, 37:5719-5734. 
10. Yuan J, Ng WH, Yap J, Chia B, Huang X, Wang M, Hu J: The AMPK inhibitor overcomes the paradoxical effect of RAF inhibitors through blocking phospho-Ser-621 in the C terminus of CRAF. J Biol Chem 2018, 293:14276-14284. 
11. Hu J, Stites EC, Yu H, Germino EA, Meharena HS, Stork PJS, Kornev AP, Taylor SS, Shaw AS: Allosteric activation of functionally asymmetric RAF kinase dimers. Cell 2013, 154:1036-1046. 
12. Hu J, Yu H, Kornev AP, Zhao J, Filbert EL, Taylor SS, Shaw AS: Mutation that blocks ATP binding creates a pseudokinase stabilizing the scaffolding function of kinase suppressor of Ras, CRAF and BRAF. Proc Natl Acad Sci U S A 2011, 108:6067-6072.