Doxorubicin downregulates cell surface B7-H1 expression and upregulates its nuclear expression in breast cancer cells: role of B7-H1 as an anti-apoptotic molecule

Abstract

IntroductionB7-H1 (PD-L1, CD274) is a T cell inhibitory molecule expressed in many types of cancer, leading to immune escape of tumor cells. Indeed, in previous reports we have shown an association of B7-H1 expression with high-risk breast cancer patients.MethodsIn the current study, we used immunohistochemistry, immunofluorescence and Western blot techniques to investigate the effect of neoadjuvant chemotherapy on the expression of B7-H1 in breast cancer cells.ResultsAmong tested chemotherapeutic agents, doxorubicin was the most effective in downregulating cell surface expression of B7-H1 in vitro. These results were validated in vivo in a xenograft mouse model, as well as in murine heart tissue known to constitutively express B7-H1. The doxorubicin-dependent cell surface downregulation of B7-H1 was accompanied by an upregulation of B7-H1 in the nucleus. This re-distribution of B7-H1 was concurrent with a similar translocation of phosphorylated AKT to the nucleus. Inhibition of the PI3K/AKT pathway abrogated the doxorubicin-mediated nuclear up-regulation of B7-H1, suggesting an involvement of PI3K/AKT pathway in the nuclear up-regulation of B7-H1. Interestingly, siRNA knock down of B7-H1 lead to an increase in spontaneous apoptosis, as well as doxorubicin-induced apoptosis, which indicates an anti-apoptotic role for B7-H1 in breast cancer cells. The novel discovery of B7-H1 expression in the nuclei of breast cancer cells suggests that B7-H1 has functions other than inhibition of T cells.ConclusionsOur findings explain the previously reported immunomodulatory effect of anthracyclines on cancer cells, and provide a link between immunoresistance and chemoresistance. Finally these results suggest the use of dual combinatorial agents to inhibit B7-H1 beside chemotherapy, in breast cancer patients.

Noninvasive Imaging of Tumor PD-L1 Expression Using Radiolabeled Anti–PD-L1 Antibodies

“…Second, it allows monitoring of expression during the course of disease, without the need of repetitive biopsies. This is of clinical importance because PD-L1 expression can change during the course of disease, due to disease progression and/or the effects of treatment (15,18,19). Third, in vivo imaging techniques also take into account the in vivo target accessibility for agents that are administered systemically.…”

“…For example, IFNg and TNFa can upregulate PD-L1 expression whereas vascular endothelial growth factor (VEGF) can downregulate tumor PD-L1 expression (15)(16)(17). Also, certain chemotherapeutics such as doxorubicin can decrease the expression of PD-L1 on the tumor cell surface, whereas radiotherapy and paclitaxel are capable of upregulating PD-L1 expression (18)(19)(20). There are no strict criteria to define PD-L1 positivity by IHC (e.g., cytoplasmic vs. membranous staining, number of positive tumor cells), and misinterpretation may occur due to heterogeneous expression within or between tumor lesions (e.g., primary vs. metastatic lesions; refs.…”

Coinhibitory molecules in hematologic malignancies: targets for therapeutic intervention

“…37,39 Interestingly, PD-L1 is also able to bind CD80, mediating T-cell inhibition. 40 In addition to downstream signaling of PD-L1, 41 also engagement of PD-L2 resulted in T-cell inhibition, further illustrating the complexity of these interactions. 42 It has been well demonstrated that PD-1 plays a crucial role in T-cell regulation in various immune responses, such as peripheral tolerance, autoimmunity, infection, and antitumor immunity.…”

PD‐L1 promotes OCT4 and Nanog expression in breast cancer stem cells by sustaining PI3K/AKT pathway activation

“…However, beside its established role in the immune response, PD‐L1 expression has intrinsic effect on cancer cells themselves (reviewed by Ritprajak et al 67, 8…”