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 4

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

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ΔNp63 promotes tumor growth, progression, and metastasis in mouse TNBC. ...
(A) Western blot shows ΔNp63 (ΔN) protein expression in EpRas cells after shRNA lentivirus vector–mediated knockdown (KD). (B) EpRas control and ΔNp63-KD EpRas cells (5 × 104) were injected into the mammary fat pad of BALB/c mice. Schematic shows experimental approach (left) and tumor growth curve (right). Ctrl, n = 8 tumors; ΔN-KD, n = 6 tumors. (C) Representative H&E images of lung show metastatic nodule of indicated groups. n = 5 mice per group. (D) EpRas cells (2 × 104) were injected into the bloodstream of BALB/c mice via tail vein (TV) to study metastasis. Representative images show lung nodules (left), and scatter plot (right) represents quantification. (E) Representative IHC images show the expression of cell proliferation (Ki67) in control and ΔNp63-KD EpRas primary tumors. Scatter plots (right) represents quantification. (F and G) Representative IF images show myeloid cell infiltration (S100A8) in the primary tumor (F) and lung metastatic site (G). Scatter plots (right) represent quantification of S100A8+ myeloid cells. (B) Two-way ANOVA was performed followed by Bonferroni post-test to compute P value. (C) Mann-Whitney U test was used to compute P value. (D–G) Student’s t test was used to compute P values. Scale bars: 40 μm (C and E–G) and 500 μm (D). Data are presented as the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, #NS. (E–G) n = 3 samples were used, and several random fields per sample were evaluated for quantification from 3 independent experiments.