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Oncogene. 2019 May;38(21):4047-4060. doi: 10.1038/s41388-019-0700-2. Epub 2019 Jan 31.

WNT signaling modulates PD-L1 expression in the stem cell compartment of triple-negative breast cancer.

Author information

1
Molecular Targeting Unit, Department of Research, Fondazione IRCCS Istituto Nazionale dei Tumori di Milano, Milan, Italy.
2
Tumor Immunology Unit, Department of Health Science, Human Pathology Section, University of Palermo School of Medicine, Palermo, Italy.
3
Molecular Immunology Unit, Department of Research, Fondazione IRCCS Istituto Nazionale dei Tumori di Milano, Milan, Italy.
4
Unit of Immunotherapy and Anticancer Innovative Therapeutics, Department of Medical Oncology and Hematology, Fondazione IRCCS Istituto Nazionale dei Tumori di Milano, Milan, Italy.
5
Cancer Genomics Laboratory, National Institute of Genomic Medicine, Mexico City, Mexico.
6
Unit of Immunotherapy and Anticancer Innovative Therapeutics, Department of Medical Oncology and Hematology, Fondazione IRCCS Istituto Nazionale dei Tumori di Milano, Milan, Italy. massimo.dinicola@istitutotumori.mi.it.
7
Molecular Targeting Unit, Department of Research, Fondazione IRCCS Istituto Nazionale dei Tumori di Milano, Milan, Italy. serenella.pupa@istitutotumori.mi.it.

Abstract

Triple-negative breast cancers (TNBCs) are characterized by a poor prognosis and lack of targeted treatments, and thus, new therapeutic strategies are urgently needed. Inhibitors against programmed death-1 (PD-1)/PD-1 ligand (PD-L1) have shown significant efficacy in various solid cancers, but their activity against TNBCs remains limited. Here, we report that human TNBCs molecularly stratified for high levels of PD-L1 (PD-L1High) showed significantly enriched expression of immune and cancer stemness pathways compared with those with low PD-L1 expression (PD-L1Low). In addition, the PD-L1High cases were significantly associated with a high stemness score (SSHigh) signature. TNBC cell lines gated for aldehyde dehydrogenase (ALDH) and CD44 stemness markers exhibited increased levels of PD-L1 versus their ALDH-negative and CD44Low counterparts, and PD-L1High cells generated significantly more mammospheres than PD-L1Low cells. Murine mammary SCA-1-positive tumor cells with PD-L1High expression generated tumors in vivo with higher efficacy than PD-L1Low cells. Furthermore, treatment of TNBC cells with selective WNT inhibitors or activators downregulated or upregulated PD-L1 expression, respectively, implying a functional cross-talk between WNT activity and PD-L1 expression. Remarkably, human TNBC samples contained tumor elements co-expressing PD-L1 with ALDH1A1 and/or CD44v6. Additionally, both PD-L1-/SCA1-positive and ALDH1A1-positive tumor elements were found in close contact with CD3-, and PD-1-positive T cells in murine and human tumor samples. Overall, our study suggests that PD-L1-positive tumor elements with a stemness phenotype may participate in the complex dynamics of TNBC-related immune evasion, which might be targeted through WNT signaling inhibition.

PMID:
30705400
PMCID:
PMC6755989
DOI:
10.1038/s41388-019-0700-2
[Indexed for MEDLINE]
Free PMC Article

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