Inhibitors of PD-1/PD-L1 and ERK1/2 impede the proliferation of receptor positive and triple-negative breast cancer cell lines

Abstract

Purpose Triple-negative breast cancer (TNBC) is characterized by an unfavorable prognosis and missing systemic therapeutic approaches beside chemotherapy. Targeting the immune checkpoint PD-1/PD-L1 showed promising results in breast cancer and especially in TNBC. The extracellular signal-regulated kinase 1/2 (ERK1/2) is an important driver of carcinogenesis. Here, the effect of combined PD-1/PD-L1 and ERK1/2 inhibitor treatment is investigated of cell growth and intracellular impact of breast cancer cell lines. Methods The IC50 values of each inhibitor and the effect of combined treatment were determined in three TNBC cell lines of different subtypes and one non-TNBC cell line. Phospho-specific antibodies were used in western blot analyses to investigate an effect on ERK1/2 activation. Expressions of immune modulatory and cell cycle-associated genes were examined by quantitative reverse transcription PCR. Results Both inhibitors PD-1/PD-L1 and ERK1/2 impeded the proliferation of TNBC to a higher extent than of non-TNBC. By combined treatment, cell lines were inhibited either synergistically or additively. ERK1/2 and S6 phosphorylation were reduced and expressions of c-Fos and FosL were diminished after ERK1/2 inhibitor as single and combined treatment. Between genes involved in immune modulation, IL-8 was upregulated in TNBC cells after combined treatment. Conclusion In conclusion, combination of PD-1/PD-L1 and ERK1/2 inhibitors showed favorable effects for a new therapy strategy, with better results in TNBC cell lines than in non-TNBC cells. The effects have to be validated in models that can reflect the interaction between immune and tumor cells like the situation in the tumor micro-environment.

Advances in immunotherapy for triple-negative breast cancer

“…Certain studies have reported that PD-L1 is present in around 20–30% of cases of TNBC, and is associated with lymphocyte infiltration and histological grades. In combination with extracellular signal-regulated kinase 1/2 inhibitors, PD-1/PD-L1 inhibitors show greater effects in TNBC cell lines than in non-TNBC cells [ 52 ]. Phase I clinical trial KEYNOTE-012 showed that pembrolizumab has good safety and object response rate (ORR) in TNBC patients [ 53 ].…”

Interrogating ligand-receptor interactions using highly sensitive cellular biosensors

“…We also investigated if the PD1-ζ biosensor cells could be used to test the potency of small molecule inhibitors of the PD1/PD-L1 interaction. Therefore, the compounds INCB 22 , I3 23 , BMS1 24 and BMS202 25 , 26 were analyzed in the PD1-ζ biosensor assay. INCB proved to be more effective than I3 (IC 50 2.3 nM vs. 162 nM) (Supplementary Fig.…”

Tumor-Associated Macrophages: Key Players in Triple-Negative Breast Cancer

“…PD-L1 is the receptor of PD-1, which is mostly expressed on the surface of tumor cells and macrophages (61,(64)(65)(66). TNBC cells can highly express PD-L1 so that their T cell killing effect in the tumor environment is significantly inhibited (56,(67)(68)(69)(70). TAMs can secrete a variety of cytokines in the TNBC environment, which mediate their immunosuppressive and tumor-promoting activities (71)(72)(73).…”