Abstract | PURPOSE: METHODS: Expression analyses were performed in both pre-treatment and NACT treated TNBC samples using immunohistochemistry and qRT-PCR, along with DNA copy number variation (CNV) and promoter methylation analyses to elucidate the mechanism(s) underlying chemo-tolerance. In addition, in vitro validation experiments were performed in TNBC cells followed by in vivo clinicopathological correlation analyses. RESULTS: A reduced expression (41.1%) of nuclear beta-catenin together with a low proliferation index was observed in NACT samples, whereas a high expression (59.0%) was observed in pre-treatment samples. The reduced nuclear expression of beta-catenin in the NACT samples showed concordance with reduced expression levels (47-52.9%) of its associated receptors (FZD7 and LRP6) and increased expression levels (35.2-41.1%) of its antagonists (SFRP1, SFRP2, DKK1) compared to those in the pre-treatment samples. The expression levels of the receptors showed no concordance with its respective gene copy number/ mRNA expression statuses, regardless treatment. Interestingly, however, significant increases in promoter hypomethylation of the antagonists were observed in the NACT samples compared to the pre-treatment samples. Similar expression patterns of the antagonists, receptors and beta-catenin were observed in the TNBC-derived cell line MDA-MB-231 using the anthracyclines doxorubicin and nogalamycin, suggesting the importance of promoter hypomethylation in chemotolerance. NACT patients showing reduced receptor and/or beta-catenin expression levels and high antagonist expression levels exhibited a comparatively better prognosis than the pre-treatment patients. CONCLUSIONS: Our data suggest that reduced nuclear expression of beta-catenin in NACT TNBC samples, due to downregulation of its receptors and upregulation of its antagonists through promoter hypomethylation of the WNT pathway, plays an important role in chemo-tolerance.
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Authors | Saimul Islam, Hemantika Dasgupta, Mukta Basu, Anup Roy, Neyaz Alam, Susanta Roychoudhury, Chinmay Kumar Panda |
Journal | Cellular oncology (Dordrecht)
(Cell Oncol (Dordr))
Vol. 43
Issue 4
Pg. 725-741
(Aug 2020)
ISSN: 2211-3436 [Electronic] Netherlands |
PMID | 32430683
(Publication Type: Journal Article)
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Chemical References |
- Antineoplastic Agents
- CTNNB1 protein, human
- beta Catenin
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Topics |
- Adult
- Aged
- Antineoplastic Agents
(therapeutic use)
- DNA Methylation
(genetics)
- Down-Regulation
- Drug Resistance, Neoplasm
(physiology)
- Female
- Humans
- Middle Aged
- Neoadjuvant Therapy
- Prognosis
- Triple Negative Breast Neoplasms
(drug therapy, genetics, metabolism)
- Wnt Signaling Pathway
(physiology)
- beta Catenin
(metabolism)
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