Targeting the PELP1-KDM1 axis as a potential therapeutic strategy for breast cancer.
BACKGROUND
The estrogen receptor (ER) co-regulator proline glutamic acid and leucine-rich protein 1 (PELP1) is a proto-oncogene that modulates epigenetic changes on ER target gene promoters via interactions with lysine-specific histone demethylase 1 (KDM1). In this study, we assessed the therapeutic potential of targeting the PELP1-KDM1 axis in vivo using liposomal (1,2-dioleoyl-sn-glycero-3-phosphatidylcholine; DOPC) siRNA to downregulate PELP1 expression and KDM1 inhibitors, pargyline and N-((1S)-3-(3-(trans-2-aminocyclopropyl)phenoxy)-1-(benzylcarbamoyl)propyl)benzamide using preclinical models.


METHODS
Preclinical xenograft models were used to test the efficacy of drugs in vivo. Ki-67 and terminal deoxynucleotidyl transferase dUTP nick end-labeling immunohistochemical analysis of epigenetic markers was performed on tumor tissues. The in vitro effect of PELP1-KDM axis blockers was tested using proliferation, reporter gene, chromatin immunoprecipitation and real-time RT-PCR assays. The efficacy of the KDM1 targeting drugs alone or in combination with letrozole and tamoxifen was tested using therapy-resistant model cells.


RESULTS
Treatment of ER-positive xenograft-based breast tumors with PELP1-siRNA-DOPC or pargyline reduced tumor volume by 58.6% and 62%, respectively. In a postmenopausal model, in which tumor growth is stimulated solely by local estrogen synthesis, daily pargyline treatment reduced tumor volume by 78%. Immunohistochemical analysis of excised tumors revealed a combined decrease in cellular proliferation, induction of apoptosis and upregulation of inhibitory epigenetic modifications. Pharmacological inhibition of KDM1 in vitro increased inhibitory histone mark dimethylation of histone H3 at lysine 9 (H3K9me2) and decreased histone activation mark acetylation of H3K9 (H3K9Ac) on ER target gene promoters. Combining KDM1 targeting drugs with current endocrine therapies substantially impeded growth and restored sensitivity of therapy-resistant breast cancer cells to treatment.


CONCLUSIONS
Our results suggest inhibition of PELP1-KDM1-mediated histone modifications as a potential therapeutic strategy for blocking breast cancer progression and therapy resistance.
Valerie
V
Cortez
Monica
M
Mann
Seshidhar
S
Tekmal
Takayoshi
T
Suzuki
Naoki
N
Miyata
Cristian
C
Rodriguez-Aguayo
Gabriel
G
Lopez-Berestein
Anil K
AK
Sood
Ratna K
RK
Vadlamudi
D000818:Animals; D001549:Benzamides / Q000008:administration & dosage / Q000494:pharmacology; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D002273:Carcinogens; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D056970:Co-Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D003521:Cyclopropanes / Q000008:administration & dosage / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D044127:Epigenesis, Genetic; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D055785:Gene Knockdown Techniques; D056466:Histone Demethylases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D051379:Mice; D058990:Molecular Targeted Therapy; D010293:Pargyline / Q000494:pharmacology; D000090063:Proto-Oncogene Mas; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
C562353:2-(3-(3-benzamido-4-(benzylamino)-4-oxobutoxy)phenyl)cyclopropylamine; D001549:Benzamides; D002273:Carcinogens; D056970:Co-Repressor Proteins; D003521:Cyclopropanes; D004967:Estrogens; D006657:Histones; C000715470:MAS1 protein, human; C438485:PELP1 protein, human; D000090063:Proto-Oncogene Mas; D014157:Transcription Factors; D010293:Pargyline; D056466:Histone Demethylases; C495195:KDM1A protein, human