Scientists Reveal the Anti-Tumor Mechanism of Src Inhibitors in IDH Mutant Cholangiocarcinoma

Background Introduction

In recent years, the incidence of intrahepatic cholangiocarcinoma (ICC) has been rising worldwide. ICC is a highly invasive tumor usually lacking noticeable symptoms in the early stages, with cases often being inoperable by the time they are diagnosed in the later stages. Currently, for unresectable ICC, the common treatment regimen is chemotherapy with gemcitabine combined with cisplatin. Recently, the U.S. Food and Drug Administration (FDA) approved the combination of Durvalumab with gemcitabine and cisplatin. Despite advances in treatment, the 5-year survival rate for ICC remains low, at just 9%.

Genomic screening studies have found that many ICC cases harbor gene mutations that can serve as therapeutic targets, with mutations in isocitrate dehydrogenase ¹⁄₂ (IDH1/2) occurring in 18%-37% of ICC cases in North America and Europe. These mutations produce an oncogenic metabolite called R(-)-2-Hydroxyglutarate (R(-)-2-HG), which inhibits α-Ketoglutarate-dependent dioxygenases, leading to massive genomic changes and impairing cholangiocyte differentiation.

Research Source

This study was authored by Iris S. Luk, Caroline M. Bridgwater, and others from multiple research institutions, including Fred Hutchinson Cancer Center (Seattle, USA) and Vall d’Hebron Institute of Oncology (Barcelona, Spain). The article was published on May 15, 2024, in Science Translational Medicine.

Research Process

The research process consists of five main steps:

1. Research Methods and Materials

The study used six human ICC cell lines, three of which were IDH wild-type and three IDH mutant types. Researchers treated the cells with the Src kinase inhibitor Dasatinib, analyzing its effect on cell proliferation and signal transduction. They assessed changes in pathway activity using immunofluorescence staining and immunoblotting and conducted knockdown and knockout experiments on key genes using RNA interference and CRISPR-Cas9 gene editing technology.

2. Phosphoproteomics Screening

Researchers conducted mass spectrometry-based phosphoproteomics screening to identify phosphoproteins significantly altered after Dasatinib treatment. Membrane-associated guanylate kinase, WW, and PDZ domain-containing protein 1 (MAGI1) were identified as an important substrate of Src kinase in IDH mutant ICC.

3. Functional Validation of MAGI1-PP2A Complex

Using biochemical and functional assays, researchers demonstrated that Src kinase activates the S6K/S6 signaling pathway by inhibiting the tumor suppressor function of the MAGI1-Protein Phosphatase 2A (PP2A) complex, promoting the growth of IDH mutant ICC. By inhibiting Src kinase, PP2A was activated, dephosphorylating S6K, thereby inducing cell death.

4. Experimental Results

The study results indicated that Dasatinib’s growth-inhibitory effect on IDH mutant ICC cells was more pronounced than on IDH wild-type cells, particularly in inhibiting S6K and S6 phosphorylation and protein synthesis. Additionally, it was confirmed that MAGI1 is a key substrate of Src kinase, and the inhibition of S6K by the MAGI1-PP2A complex is a crucial part of this anti-tumor mechanism.

5. Conclusion and Application Value

The study elucidated the mechanism of Dasatinib in IDH mutant ICC, revealing a signaling complex regulating S6K phosphorylation, independent of the mTOR signaling pathway. The research also suggested a combination therapy of Dasatinib with S6K/AKT inhibitors (like M2698) significantly reducing phosphorylated S6 in IDH mutant ICC cell lines and patient-derived organoids, thus inhibiting tumor growth. This discovery may offer practical clinical treatment options.

Research Highlights and Significance

Key Findings

1. Critical Role of Src Kinase: For the first time, the study revealed that Src kinase regulates the S6K/S6 signaling pathway through the MAGI1-PP2A complex, promoting the growth of IDH mutant ICC.
2. Inhibition of S6K/S6 Signaling Pathway: This study demonstrated that inhibiting Src kinase could activate PP2A, thereby dephosphorylating S6K and S6, inhibiting protein synthesis, and causing cell death.
3. Combination Therapy Strategy: A new strategy of combining Dasatinib with S6K/AKT inhibitors was proposed, effectively overcoming both intrinsic and acquired resistance to Dasatinib.

Scientific Value and Application Prospects

This study not only enhances the understanding of the pathological mechanisms of IDH mutant ICC but also provides new therapeutic targets and strategies, offering valuable insights for future clinical treatments. The combined use of Dasatinib and S6K/AKT inhibitors may become an effective means to treat this aggressive cancer, improving patient survival rates and quality of life.

Other Valuable Information

Additionally, the study found that the presence of 2-HG is crucial for inhibiting the S6K/S6 signaling pathway, suggesting that in clinical treatment, careful consideration is needed for the combined or sequential use of Dasatinib and other IDH1/2 inhibitors to avoid resistance due to drug interactions. This article not only provides new ideas and methods for the treatment of cholangiocarcinoma but also brings hope and inspiration for personalized cancer treatment in the future.