How to improve the efficacy and reverse the resistance to
epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), such as
erlotinib, remains a major challenge in the targeted
therapy of
lung adenocarcinoma with EGFR-activating mutation.
Phosphoglycerate dehydrogenase (PHGDH) is the key
enzyme of de novo
serine biosynthesis over-expressed in various types of
cancer including
lung cancer. Elevated PHGDH expression is correlated with a worse overall survival in clinical
lung adenocarcinoma patients. Here we investigated the role of PHGDH in
lung adenocarcinoma with the acquisition of resistance to
erlotinib. Methods: The necessary genes required for the acquired
erlotinib resistance in
lung adenocarcinoma cells were screened out by
RNA-Seq analysis. Then the
protein and
mRNA levels of PHGDH were confirmed by immunoblotting and qRT-PCR in the
erlotinib resistant cells. The effects of PHGDH inhibition or overexpression on
erlotinib resistance were examined using cell culture and
tumor xenograft mouse models respectively. To explore mechanism, the ROS level and DNA damage marker, γH2AX, were tested by
DCFH-DA staining and immunofluorescence after PHGDH inhibition. Results: We found that PHGDH level was significantly increased in the
lung adenocarcinoma PC9ER4 and HCC827ER9 cells that acquired resistance to
erlotinib. Perturbation of PHGDH by siPHGDH transfection or
NCT-503, a small molecular PHGDH inhibitor, synergistically augmented the tumoricidal effect and restored sensitivity to
erlotinib in cell lines and xenografts. Over-expression of PHGDH caused xenografts resistant to
erlotinib. Furthermore, multiple DNA damage repair pathways related genes were changed by PHGDH depletion specifically in
erlotinib resistant cells. ROS stress and DNA damage marker γH2AX were enhanced by siPHGDH and
NCT-503, which was reversed by NAC. Conclusion: Our study indicated that PHGDH inhibition has potential therapeutic value in
lung adenocarcinoma with the acquired resistance to EGFR-TKIs.