Premium
Changes in DNA Damage Response Proteins During Tamoxifen Treatment and Resistance
Author(s) -
Vergne Ralphdy,
OrtizSanchez Carmen,
GodoyMunoz Lenin Jose,
Encarnación Jarline,
Matta Jaime
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.996.1
Subject(s) - dna damage , tamoxifen , dna repair , dna , cancer research , estrogen receptor , biology , microbiology and biotechnology , chemistry , breast cancer , cancer , biochemistry , genetics
Tamoxifen (TMX) is currently used for the treatment of both early and advanced estrogen receptor positive (ER+) breast cancer in pre‐ and post‐menopausal women. TMX works by blocking the actions of estrogen and preventing proliferation and furthermore, cell death. DNA damage is an alteration of chemical structure of the DNA that activates a network of proteins to start several cellular processes that sense, detect signal and repair DNA lesions. The mechanism of action of several chemotherapeutic drugs is based on damaging the DNA of the cancerous cell. Although TMX's mechanism of action is not through DNA damage, TMX treatment can lead to the production of oxidative stress that in consequence can affect and damage DNA. Our aim is to study the DNA damage induced by TMX resistance in ER+ breast cancer cell line (MCF‐7) cells and assess the expression changes of key proteins involved in this response. Our hypothesis is that there will be more DNA damage in cells treated with TMX in comparison to untreated cells, and the DNA damage contributes to resistance against TMX. To achieve this, we will assess ER expression as an indicator of resistance to TMX, analyze DNA damage during TMX treatment, and study protein expression related to DNA damage using MCF‐7 under TMX. To achieve this, we cultured MCF‐7 cells using complete media without phenol red and 0.5 μM of TMX with 10 μL of insulin. After 1 week, cells were lysed for protein and RNA extraction. Our results shows that ERα expression was similar to untreated cells; therefore, no statistically differences p>0.05 were found. To assess protein expression changes in proteins involved in DNA damage, we assessed PTEN expression by Western blot. Although, no statistically significant differences were found when comparing TMX treated cells with untreated cells (p>0.05) we observed a slight expression change. This preliminary data indicates that PTEN expression might be affected in ER+ breast cancer cells when TMX resistance is developed. Currently, we are developing an MCF‐7 cell line resistant to TMX for additional studies and assessing protein expression changes of other candidates involved in DNA damage response (such as BRCA‐2 and XPF). These results will shed light on the effect of TMX resistance in the DNA damage response of ER+ breast cancer cells. Also, they will allow us to get an inside view and to track the changes in MCF‐7 protein expression during the TMX resistance timeframe. Support or Funding Information Funded by NIH‐NIGMS #2R25GM096955 (UPRP‐Rise program) Supported by grants from the NCI Center to Reduce Health Disparities and NIH‐NIGMS MBRS Program grant #9SC1CA182846‐04 (J. Matta Laboratory) We also want to acknowledge the support of the Molecular and Genomics Core Laboratory at Ponce Health Sciences University‐Ponce Research Institute (Grant MD00757).