Deglycosylation of PD-L1 by 2-deoxyglucose reverses PARP inhibitor-induced immunosuppression in triple-negative breast cancer.
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ABSTRACT:
SUBMITTER: Shao B
PROVIDER: S-EPMC6176188 | biostudies-literature | 2018
REPOSITORIES: biostudies-literature
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Project description:Poly (ADP-ribose) polymerase (PARP) inhibitors have emerged as promising targeted therapies for BRCA-mutated cancers by blocking repair of DNA double-strand breaks. However, resistance to PARP inhibitors (PARPi) has been described in some patients lowering the overall response rates. To investigate the underlying mechanisms of PARPi resistance, we developed the adaptive resistant clones in triple-negative breast cancer cell lines. We identified epithelial-mesenchymal transition (EMT) and upregulation of programmed death-ligand 1 (PD-L1) in resistant cells and further demonstrated the important role of Akt S473 phosphorylation in PARPi resistance. In addition, PARPi mediated EMT is independent of PD-L1 upregulation. Blocking the p-Akt S473 axis by metformin reversed EMT and PD-L1 expression which sensitized PARPi-resistant cells to cytotoxic T cells. Thus, a combination of metformin and PARP inhibitors may be a promising therapeutic strategy to increase the efficacy of PARP inhibitors and tumor sensitivity to immunotherapy.
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Project description:Hypoxia plays an extensive role in the development of the tumor microenvironment (TME), particularly in mediating immunosuppression. Respiratory hyperoxia therapy has the potential to improve the effects of conventional cancer therapies via molecular mechanisms mediating antitumor immunity. Here, we investigated whether hyperoxia therapy can restore tumor immunity and inhibit lung metastases in a mouse model of triple-negative breast cancer (TNBC) by treating a 4T1 mammary carcinoma mouse model with normoxia (21% oxygen) or hyperoxia (60% oxygen) therapy, after tumor development. Using flow cytometry analysis, we observed significant organ-specific expansion of myeloid-derived suppressor cells (MDSCs) and protein expression upregulation of the programmed death-ligand 1 (PD-L1) in the hypoxic TME of 4T1 tumor-bearing mice maintained under normoxia conditions, with the TME converting to a T-cell immune-suppressive state as early as the premetastatic phase. Markedly, hyperoxia treatments ameliorated hypoxia levels in the lung TME and decreased the proportion of MDSCs and the expression of PD-L1 in both the primary tumor and in the metastatic lung, when compared to animals treated with respiratory normoxia therapy. In addition, the number of lung metastatic nodes fell from 90 per lung in the normoxic treated group to 13 per lung in the hyperoxic treated group (P < 0.05), with the latter having limited hyperoxia effects on primary tumor growth (mammary glands). Notably, hyperoxia therapy was characterized by the differential recruitment of CD4+ and CD8+ T-cells. Thus, our study confirms that hyperoxia therapy may be used to overcome TME immunosuppression and control the extend of lung metastases in TNBC. Importantly, changes in immunosuppressive MDSCs frequency and PD-L1 expression levels may serve as biomarkers of hypoxia levels in cancer affected tissues that can benefit from hyperoxia treatments.
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Project description:Early-phase trials targeting the T-cell inhibitory molecule programmed cell death ligand 1 (PD-L1) have shown clinical efficacy in cancer. This study was undertaken to determine whether PD-L1 is overexpressed in triple-negative breast cancer (TNBC) and to investigate the loss of PTEN as a mechanism of PD-L1 regulation. The Cancer Genome Atlas (TCGA) RNA sequencing data showed significantly greater expression of the PD-L1 gene in TNBC (n = 120) compared with non-TNBC (n = 716; P < 0.001). Breast tumor tissue microarrays were evaluated for PD-L1 expression, which was present in 19% (20 of 105) of TNBC specimens. PD-L1(+) tumors had greater CD8(+) T-cell infiltrate than PD-L1(-) tumors (688 cells/mm vs. 263 cells/mm; P < 0.0001). To determine the effect of PTEN loss on PD-L1 expression, stable cell lines were generated using PTEN short hairpin RNA (shRNA). PTEN knockdown led to significantly higher cell-surface PD-L1 expression and PD-L1 transcripts, suggesting transcriptional regulation. Moreover, phosphoinositide 3-kinase (PI3K) pathway inhibition using the AKT inhibitor MK-2206 or rapamycin resulted in decreased PD-L1 expression, further linking PTEN and PI3K signaling to PD-L1 regulation. Coculture experiments were performed to determine the functional effect of altered PD-L1 expression. Increased PD-L1 cell surface expression by tumor cells induced by PTEN loss led to decreased T-cell proliferation and increased apoptosis. PD-L1 is expressed in 20% of TNBCs, suggesting PD-L1 as a therapeutic target in TNBCs. Because PTEN loss is one mechanism regulating PD-L1 expression, agents targeting the PI3K pathway may increase the antitumor adaptive immune responses.
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Project description:(1) Background: Triple-negative breast cancer (TNBC) is a distinct subgroup of breast cancer presenting a high level of recurrence, and neo-adjuvant chemotherapy is beneficial in its therapy management. Anti-PD-L1 immunotherapy improves the effect of neo-adjuvant therapy in TNBC. (2) Methods: Immune-modulation and ferroptosis-related R-packages were developed for integrative omics analyses under ferroptosis-inducer treatments: TNBC cells stimulated with ferroptosis inducers (GSE173905, GSE154425), single cell data (GSE191246) and mass spectrometry on breast cancer stem cells. Clinical association analyses were carried out with breast tumors (TCGA and METABRIC cohorts). Protein-level validation was investigated through protein atlas proteome experiments. (3) Results: Erastin/RSL3 ferroptosis inducers upregulate CD274 in TNBC cells (MDA-MB-231 and HCC38). In breast cancer, CD274 expression is associated with overall survival. Breast tumors presenting high expression of CD274 upregulated some ferroptosis drivers associated with prognosis: IDO1, IFNG and TNFAIP3. At the protein level, the induction of Cd274 and Tnfaip3 was confirmed in breast cancer stem cells under salinomycin treatment. In a 4T1 tumor treated with cyclophosphamide, the single cell expression of Cd274 was found to increase both in myeloid- and lymphoid-infiltrated cells, independently of its receptor Pdcd1. The CD274 ferroptosis-driver score computed on a breast tumor transcriptome stratified patients on their prognosis: low score was observed in the basal subgroup, with a higher level of recurrent risk scores (oncotypeDx, ggi and gene70 scores). In the METABRIC cohort, CD274, IDO1, IFNG and TNFAIP3 were found to be overexpressed in the TNBC subgroup. The CD274 ferroptosis-driver score was found to be associated with overall survival, independently of TNM classification and age diagnosis. The tumor expression of CD274, TNFAIP3, IFNG and IDO1, in a biopsy of breast ductal carcinoma, was confirmed at the protein level (4) Conclusions: Ferroptosis inducers upregulate PD-L1 in TNBC cells, known to be an effective target of immunotherapy in high-risk early TNBC patients who received neo-adjuvant therapy. Basal and TNBC tumors highly expressed CD274 and ferroptosis drivers: IFNG, TNFAIP3 and IDO1. The CD274 ferroptosis-driver score is associated with prognosis and to the risk of recurrence in breast cancer. A potential synergy of ferroptosis inducers with anti-PD-L1 immunotherapy is suggested for recurrent TNBC.
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Project description:Although poly(ADP-ribose) polymerase (PARP) inhibitors are active in homologous recombination (HR)-deficient cancers, their utility is limited by acquired resistance after restoration of HR. Here, we report that dinaciclib, an inhibitor of cyclin-dependent kinases (CDKs) 1, 2, 5, and 9, additionally has potent activity against CDK12, a transcriptional regulator of HR. In BRCA-mutated triple-negative breast cancer (TNBC) cells and patient-derived xenografts (PDXs), dinaciclib ablates restored HR and reverses PARP inhibitor resistance. Additionally, we show that de novo resistance to PARP inhibition in BRCA1-mutated cell lines and a PDX derived from a PARP-inhibitor-naive BRCA1 carrier is mediated by residual HR and is reversed by CDK12 inhibition. Finally, dinaciclib augments the degree of response in a PARP-inhibitor-sensitive model, converting tumor growth inhibition to durable regression. These results highlight the significance of HR disruption as a therapeutic strategy and support the broad use of combined CDK12 and PARP inhibition in TNBC.
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Project description:PurposeStratification of patients with triple-negative breast cancer (TNBC) for anti-PD-L1 therapy is based on PD-L1 expression in tumor biopsies. This study sought to evaluate the risk of PD-L1 misclassification.MethodsWe conducted a high-resolution analysis on ten surgical specimens of TNBC. First, we determined PD-L1 expression pattern distribution via manual segmentation and measurement of 6666 microscopic clusters of positive PD-L1 immunohistochemical staining. Then, based on these results, we generated a computer model to calculate the effect of the positive PD-L1 fraction, aggregate size, and distribution of PD-L1 positive cells on the diagnostic accuracy.ResultsOur computer-based model showed that larger aggregates of PD-L1 positive cells and smaller biopsy size were associated with higher fraction of false results (P < 0.001, P < 0.001, respectively). Additionally, our model showed a significant increase in error rate when the fraction of PD-L1 expression was close to the cut-off (error rate of 12.1%, 0.84%, and 0.65% for PD-L1 positivity of 0.5-1.5%, ≤ 0.5% ,and ≥ 1.5%, respectively, P < 0.0001). Interestingly, false positive results were significantly higher than false negative results (0.51-22.62%, with an average of 6.31% versus 0.11-11.36% with an average of 1.58% for false positive and false negative results, respectively, P < 0.05). Furthermore, heterogeneous tumors with different aggregate sizes in the same tumor, were associated with increased rate of false results in comparison to homogenous tumors (P < 0.001).ConclusionOur model can be used to estimate the risk of PD-L1 misclassification in biopsies, with potential implications for treatment decisions.
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Project description:The limited treatment options and therapeutic failure due to acquired resistance for patients with triple-negative breast cancer (TNBC) represent a significant challenge. Inhibitors against poly (ADP-ribose) polymerase (PARP), olaparib and talazoparib, were recently approved for the treatment of metastatic breast cancer (including TNBC) in patients with germline BRCA1/2 mutations. Despite impressive response rates of ~60%, the prolongation in median progression-free survival with a PARPi is modest, suggesting the emergence of resistance. Several studies have reported that receptor tyrosine kinases (RTKs), such as c-MET (also known as hepatocyte growth factor receptor), are involved in resistance to various anti-neoplastic agents, including PARPi. However, the mechanism by which c-MET contributes to acquired resistance to PARPi in TNBC is not fully understood. In this study, we show that hyperactivated c-Met is detected in TNBC cells with acquired resistance to PARPi, and the combination of talazoparib and crizotinib (a multi-kinase inhibitor that inhibits c-MET) synergistically inhibits proliferation in these cells. Unexpectedly, depleting c-MET had limited effect on talazoparib sensitivity in PARPi-resistant cells. Interestingly, we found evidence of epidermal growth factor receptor (EGFR) hyperactivation and interaction of EGFR/c-Met in these cells. Notably, combining EGFR and PARP inhibitors resulted in greater inhibition of proliferation in c-MET-depleted TNBC cells, and combined c-MET and EGFR inhibition increased sensitivity to talazoparib in TNBC cells with acquired resistance to PARPi. Our findings suggest that combined inhibition of c-MET and EGFR could potentially re-sensitize TNBC to the cytotoxic effects of PARPi.
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