A Protein That Could Be Fueling Cancer Growth Identified
Researchers have found that a protein involved in the immune response to microbes can also fuel cancer development and suppress the response to the disease.
Working in mouse models of lung cancer, the research team found TANK-binding kinase 1 (TBK1) and its adaptor proteinTBK-binding protein 1 (TBKBP1) contribute to tumorigenesis when they are activated by growth factors rather than by innate immune mechanisms.
Recent research indicated that TBK1, which normally mediates induction of type 1 interferon in response to viruses or bacteria, also promotes the survival and reproduction of KRAS-dependent cancer cells.
For the findings published in the journal Nature Cell Biology, the research team set out to identify TBK1's impact on cancer cells and its role in cancer development in vivo.
In a series of experiments, the researchers showed that TBK1 and TBKBP1 form a growth factor signaling axis that activates mTORC1 to promote tumour development.
The pathway consists of TBKBP1 recruiting TBK1 to protein kinase C-theta (PKC), through a scaffold protein called CARD10, enabling PKC to activate TBK1.
To test the protein's therapeutic potential, the research team treated mice with KRAS-driven lung cancer with amlexanox, a drug approved by the Food and Drug Administration as a paste to treat certain oral ulcers.
KRAS-driven cancer is resistant to immune response, but the researchers found amlexanox sensitised tumours to blockade of the CTLA-4 checkpoint on immune T cells.
Knocking down TBK1 in the KRAS-driven mouse model increased the frequency of effector CD4 helper T cells and CD8 cell-killing T cells in the lungs of the mice.
A similar experiment in another mouse model also reduced the frequency of immune-suppressing myeloid-derived suppressor cells.
Additional experiments implicated TBK1 in promotion of glycolysis - a sugar-burning metabolic process that also suppresses the immune system - and the increased presence of PD-L1, a protein on tumour cells that turns off attacking T cells by connecting with the PD-1 protein on their cell surface.
"We're continuing to examine the signaling function of TBK1 in different types of immune cells using animal models and to assess the therapeutic potential of TBK1 using preclinical cancer models," Sun said.
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