A novel toll-like receptor 9 agonist cooperates with trastuzumab in trastuzumab-resistant breast tumors through multiple mechanisms of action.
OBJECTIVE
Resistance to anti-HER2 monoclonal antibody trastuzumab is a relevant issue in breast cancer patients. Among the mechanisms implicated in trastuzumab resistance, increasing evidence supports a role of tumor microenvironment. We previously found that a novel toll-like receptor 9 agonist, referred to as immune modulatory oligonucleotide (IMO) and currently under clinical investigation, acts through epidermal growth factor receptor (EGFR) and shows direct antiangiogenic effects by cooperating with anti-EGFR or anti-VEGF drugs, thus interfering with cancer cells and microenvironment.


METHODS
In this study, we used KPL-4 and JIMT-1 trastuzumab-resistant breast cancer cells to evaluate the combination IMO plus trastuzumab as a therapeutic option for trastuzumab-resistant breast cancers.


RESULTS
IMO inhibits KPL-4 and JIMT-1 xenografts growth and potentiates trastuzumab antitumor effect, with complete suppression of tumor growth, potent enhancement of trastuzumab-mediated antibody-dependent cell-mediated cytotoxicity, and strong inhibition of EGFR/HER2-related signaling. In KPL-4 xenografts, IMO alone interferes with HER signal transduction, whereas trastuzumab is ineffective. IMO induces an HER-dependent signal inhibition also in vitro by modulating a functional interaction between toll-like receptor 9 and HER receptors occurring at membrane level. Finally, IMO plus trastuzumab produces a cooperative antiangiogenic effect related to suppression of endothelial HER-related signaling.


CONCLUSIONS
We showed a cooperative effect of IMO plus trastuzumab in trastuzumab-resistant breast cancers due to IMO direct antitumor and antiangiogenic activity and antibody-dependent cell-mediated cytotoxicity enhancement. Moreover, we provided first evidence of a toll-like receptor 9/HER interaction at membrane level as novel mechanism of action. Altogether, we propose IMO plus trastuzumab as an effective strategy in trastuzumab-resistant breast cancers.
Damiano
Vincenzo
V
Departments of Endocrinologia ed Oncologia Molecolare e Clinica, and Biologia e Patologia Cellulare e Molecolare L. Califano, Università di Napoli Federico II, Napoli, Italy.
Garofalo
Sonia
S
Rosa
Roberta
R
Bianco
Roberto
R
Caputo
Rosa
R
Gelardi
Teresa
T
Merola
Gerardina
G
Racioppi
Luigi
L
Garbi
Corrado
C
Kandimalla
Ekambar R
ER
Agrawal
Sudhir
S
Tortora
Giampaolo
G
D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D019008:Drug Resistance, Neoplasm; D004730:Endothelium, Vascular / Q000166:cytology; D005260:Female; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D009841:Oligonucleotides / Q000737:chemistry; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology; D051217:Toll-Like Receptor 9 / Q000819:agonists* / Q000737:chemistry*; D000068878:Trastuzumab
D020533:Angiogenesis Inhibitors; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D009841:Oligonucleotides; D018719:Erb-b2 Receptor Tyrosine Kinases; D051217:Toll-Like Receptor 9; D000068878:Trastuzumab