(P13-21-26) Impact of Obesity Phenotype Circulating Milieu on MCF7 Cell Antioxidant Activity and Viability

Objectives: Classical obesity (BMI ≥ 30.0 kg/m²) has long been linked to increased breast cancer risk, potentially by oxidative stress-induced DNA damage. Subsequent research suggests this risk extends to nontraditional obesity phenotypes, including normal-weight obesity (NWO) and metabolically heathy obesity (MHO); yet the role of oxidative stress is unknown. Here, we explored the impact of the NWO and MHO circulating milieu (serum) on breast cancer cell antioxidant activity and viability compared to low-risk, lean controls (CON) and high-risk people with metabolically unhealthy obesity (MUO).

Methods: Female participants (N=40; n=10/group) were categorized as CON (normal BMI, metabolically healthy, low body fat %), NWO (normal BMI, high body fat %), MHO (obese BMI, metabolically healthy, high body fat %), and MUO (obese BMI, metabolically unhealthy, high body fat %). Metabolically healthy and unhealthy were defined as 0-1 and 2+ metabolic syndrome risk factors, respectively. High/low body fat % was over/under 35%. For all experiments, MCF7 cells were first cultured in DMEM (10% FBS), then FBS was replaced with 10% participant serum. NRF2 promoter activity was assessed after serum treatment alone and following pre-treatment with high-dose (250 µM) palmitate for 24h. Cell viability was also assessed under several pretreatments + subsequent serum treatment for 24h: low-dose palmitate (50 µM) for 8 wks (chronic lipotoxicity); RSL for 24h (acute oxidative stress); and doxorubicin for 24h (acute oxidative stress).

Results: After serum alone, NRF2 activity was decreased in MHO and MUO by ~50% compared to CON (p < 0.01). Conversely, following acute lipotoxic stress, NRF2 activity increased in MHO versus CON (p < 0.05). NWO and MHO serum-exposed cells had reduced cell viability compared to CON (p < 0.05; 33% and 52%, respectively) after chronic lipotoxicity. Yet, MHO serum-treated cell viability was significantly less impacted by RSL3 and doxorubicin treatment than CON (p < 0.05).

Conclusions: Obesity-associated factors differentially regulated MCF7 cell stress tolerance. NWO serum was generally reduced viability under stress. MHO serum established a relative survival advantage during acute oxidative and chemotherapeutic treatment, despite not improving baseline survival under chronic lipotoxicity.

Funding Sources: American Heart Association, NIH