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.
BACKGROUND
B7-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.


METHODS
In 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.


RESULTS
Among 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.


CONCLUSIONS
Our 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.
Ghebeh
Hazem
H
Tumor Immunology Section, King Faisal Specialist Hospital and Research Center PO Box 3354, Riyadh 11211, Saudi Arabia.
Lehe
Cynthia
C
Barhoush
Eman
E
Al-Romaih
Khaldoon
K
Tulbah
Asma
A
Al-Alwan
Monther
M
Hendrayani
Siti-Faujiah
SF
Manogaran
Pulicat
P
Alaiya
Ayodele
A
Al-Tweigeri
Taher
T
Aboussekhra
Abdelilah
A
Dermime
Said
S
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects*; D060890:B7-H1 Antigen; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects*; D015536:Down-Regulation / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D018613:Microscopy, Confocal; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
D000903:Antibiotics, Antineoplastic; D015703:Antigens, CD; D060890:B7-H1 Antigen; C423236:CD274 protein, human; D004317:Doxorubicin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt