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Oncotarget. 2017 Dec 26;9(5):6062-6074. doi: 10.18632/oncotarget.23681. eCollection 2018 Jan 19.

[Neratinib + Valproate] exposure permanently reduces ERBB1 and RAS expression in 4T1 mammary tumors and enhances M1 macrophage infiltration.

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Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA 23298, USA.
University of Pittsburgh Cancer Institute Melanoma and Skin Cancer Program, Hillman Cancer Research Pavilion Laboratory L1.32c, Pittsburgh, PA 15232, USA.
Puma Biotechnology Inc., Los Angeles, CA 90024, USA.
Department of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA.


The irreversible ERBB1/2/4 inhibitor neratinib has been shown in vitro to rapidly reduce the expression of ERBB1/2/4 and RAS proteins via autophagic/lysosomal degradation. We have recently demonstrated that neratinib and valproate interact to suppress the growth of 4T1 mammary tumors but had not defined whether the [neratinib + valproate] drug combination, in a mouse, had altered the biology of the 4T1 cells. Exposure of 4T1 mammary tumors to [neratinib + valproate] for three days resulted, two weeks later, in tumors that expressed less ERBB1, K-RAS, N-RAS, indoleamine-pyrrole 2,3-dioxygenase (IDO-1), ornithine decarboxylase (ODC) and had increased Class I MHCA expression. Tumors previously exposed to [neratinib + valproate] grew more slowly than those exposed to vehicle control and contained more CD8+ cells and activated NK cells. M1 but not M2 macrophage infiltration was significantly enhanced by the drug combination. In vitro exposure of 4T1 tumor cells to [neratinib + valproate] variably reduced the expression of histone deacetylases 1-11. In vivo, prior exposure of tumors to [neratinib + valproate] permanently reduced the expression of HDACs 1-3, 6 and 10. Combined knock down of HDACs 1/2/3 or of 3/10 rapidly reduced the expression IDO-1, and ODC and increased the expression of MHCA. H&E staining of normal tissues at animal nadir revealed no obvious cyto-architectural differences between control and drug-treated animals. We conclude that [neratinib + valproate] evolves 4T1 tumors to grow more slowly and to be more sensitive to checkpoint immunotherapy antibodies.


autophagy; neratinib; receptor tyrosine kinase; valproate

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