ΔNp63-driven recruitment of myeloid-derived suppressor cells promotes metastasis in triple-negative breast cancer
Sushil Kumar, David W. Wilkes, Nina Samuel, Mario Andres Blanco, Anupma Nayak, Kevin Alicea-Torres, Christian Gluck, Satrajit Sinha, Dmitry Gabrilovich, Rumela Chakrabarti
Sushil Kumar, David W. Wilkes, Nina Samuel, Mario Andres Blanco, Anupma Nayak, Kevin Alicea-Torres, Christian Gluck, Satrajit Sinha, Dmitry Gabrilovich, Rumela Chakrabarti
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Research Article Oncology

ΔNp63-driven recruitment of myeloid-derived suppressor cells promotes metastasis in triple-negative breast cancer

Abstract

Triple-negative breast cancer (TNBC) is particularly aggressive, with enhanced incidence of tumor relapse, resistance to chemotherapy, and metastases. As the mechanistic basis for this aggressive phenotype is unclear, treatment options are limited. Here, we showed an increased population of myeloid-derived immunosuppressor cells (MDSCs) in TNBC patients compared with non-TNBC patients. We found that high levels of the transcription factor ΔNp63 correlate with an increased number of MDSCs in basal TNBC patients, and that ΔNp63 promotes tumor growth, progression, and metastasis in human and mouse TNBC cells. Furthermore, we showed that MDSC recruitment to the primary tumor and metastatic sites occurs via direct ΔNp63-dependent activation of the chemokines CXCL2 and CCL22. CXCR2/CCR4 inhibitors reduced MDSC recruitment, angiogenesis, and metastasis, highlighting a novel treatment option for this subset of TNBC patients. Finally, we found that MDSCs secrete prometastatic factors such as MMP9 and chitinase 3–like 1 to promote TNBC cancer stem cell function, thereby identifying a nonimmunologic role for MDSCs in promoting TNBC progression. These findings identify a unique crosstalk between ΔNp63+ TNBC cells and MDSCs that promotes tumor progression and metastasis, which could be exploited in future combined immunotherapy/chemotherapy strategies for TNBC patients.

Authors

Sushil Kumar, David W. Wilkes, Nina Samuel, Mario Andres Blanco, Anupma Nayak, Kevin Alicea-Torres, Christian Gluck, Satrajit Sinha, Dmitry Gabrilovich, Rumela Chakrabarti

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Figure 2

ΔNp63 promotes tumor growth, progression, and metastasis in human TNBC.

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ΔNp63 promotes tumor growth, progression, and metastasis in human TNBC. ...
(A) Western blot shows ΔNp63 (ΔN) protein expression in control and ΔNp63-KD HCC1806 cells after shRNA lentivirus vector–mediated knockdown (KD). (B) Red fluorescence (RFP) and Renilla luciferase–expressing control and ΔNp63-KD HCC1806 cells (2 × 105) were injected into the mammary fat pad of nude mice. Representative mouse images (left) and tumor growth (right; total flux, photons per second [p/s]) show bioluminescent signal from tumors in vivo. (C) Tumor growth curves show data of palpated tumor growth of indicated groups. (B and C) n = 10 tumors per group. Contralateral mammary glands (4th position) of n = 5 mice per group were used for injection. (D and E) Control and ΔNp63-KD HCC1806 tumor-bearing mice show in vivo (D) and ex vivo (E) lung metastasis by bioluminescence imaging. Ctrl, n = 6 mice per group; ΔN-KD, n = 4 mice per group. (F) Bright-field and fluorescence images show RFP+ circulating tumor cells (CTCs) after culture. CTCs were isolated from blood of control and ΔNp63-KD HCC1806 xenograft-bearing mice and cultured for 1 week. n = 5 mice per group. (G) HCC1806 cells (2 × 105) were injected into the bloodstream of NSG mice via tail vein to study metastasis; a representative image of RFP+ lung metastatic nodules is shown (G, left, red arrows). Quantification of metastatic RFP+ nodules of indicated groups is shown at right. The insets show H&E images of sections of lung, showing metastatic nodule in control. Ctrl, n = 6 mice; ΔN-KD, n = 7 mice. (B and C) Two-way ANOVA was performed with Bonferroni post-test adjustment. (D–G) Mann-Whitney U test was used to compute P values. Scale bars: 40 μm (F) and 500 μm (G). Data are presented as the mean ± SEM from 3 independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001. FOV, field of view.