KRAS acting through ERK signaling stabilizes PD-L1 via inhibiting autophagy pathway in intrahepatic cholangiocarcinoma

Abstract

Background While the correlation between PD-L1 expression and KRAS mutation has been previously reported in other solid tumors such as non-small cell lung cancer (NSCLC), whether PD-L1 can be modulated by ERK signaling downstream of KRAS in intrahepatic cholangiocarcinoma (iCCA) and the underlying molecular regulatory mechanism remain unclear. Methods The expression of ERK, p-ERK, PD-L1 and autophagy markers following KRAS knockdown or Ras/Raf/MEK/ERK signaling inhibitors treatment was examined in two human iCCA cell lines (HuCCT1 and RBE) using western blotting and immunofluorescence. Both pharmacological autophagy inhibitors and short-interfering RNA against ATG7 were applied to inhibit autophagy. The apoptosis rates of iCCA cell lines were detected by flow cytometry and CCK-8 after co-culturing with CD3/CD28-activated human CD8+ T lymphocytes. Immunohistochemistry was applied to detect the correlation of ERK, p-ERK and PD-L1 in 92 iCCA tissues. Results The present study demonstrated that the PD-L1 expression level was distinctly reduced in KRAS-mutated iCCA cell lines when ERK signaling was inhibited and ERK phosphorylation levels were lowered. The positive association between p-ERK and PD-L1 was also verified in 92 iCCA tissue samples. Moreover, ERK inhibition induced autophagy activation. Both inhibiting autophagy via autophagy inhibitors and genetically silencing the ATG7 expression partially reversed the reduced PD-L1 expression caused by ERK inhibition. In addition, ERK-mediated down-regulation of PD-L1 via autophagy pathways induced the apoptosis of iCCA cells when co-cultured with CD3/CD28-activated human CD8+ T lymphocytes in vitro. Conclusions Our results suggest that ERK signaling inhibition contributes to the reduction of PD-L1 expression through the autophagy pathway in iCCA. As a supplement to anti-PD-1/PD-L1 immunotherapy, ERK-targeted therapy may serve as a potentially novel treatment strategy for human KRAS-mutated iCCA.

The efficacy of immune checkpoint inhibitors in biliary tract cancer with KRAS mutation

“…16,17 It is not revealed much in BTC; however, some studies showed that KRAS mutation induces the expression of PD-L1. 18,19 Our data did not show any correlation between KRAS and PD-L1 in BTC patients; However, as this study only included small number of patients, further studies would be needed.…”

Clinical Efficacy and Safety of Sintilimab Combined with Targeted Drug Therapy as Second-Line or Above Treatment for Advanced or Metastatic Gastric Cancer

“…Compared with the data from the above clinical studies of monotherapy, the results of our study demonstrated relatively better therapeutic effects, which may also be related to the low overall ECOG scores of patients. It has also been shown that some targeted drugs can improve the immunotherapy response rate by promoting the activation and recruitment of CD8 + T cells, enhancing the expression of PD-L1, and eliminating immunosuppressive tumor microenvironment (TME), thus suggesting that the combination of targeted therapy and immunotherapy plays a synergistic role, which can be used as a new therapeutic strategy 24,25,26 .…”

KRAS Mutations in Solid Tumors: Characteristics, Current Therapeutic Strategy, and Potential Treatment Exploration

“…A study based on 17,909 CRC patients found that rare KRAS mutation subtypes such as A59T were correlated with predictive immunotherapy response biomarkers [ 134 ]. The inhibition of ERK signaling was found to assist in reducing PD-L1 expression through autophagy in intrahepatic cholangiocarcinoma (iCCA), indicating that ERK-targeted therapy may be combined with anti-PD-(L)1 immunotherapy for KRAS-mutant iCCA [ 135 ]. Equipping cetuximab on the surface of NK cells may solve the problem of cetuximab resistance in KRAS-mutant CRC [ 136 ].…”