Abstract 2589: Gene signature of fluvastatin resistance for prevention of breast cancer and predicting resistance to statins
Authors: Bhardwaj Anjana , Ju Zhenlin , Embury Matthew , Wang Jing , Bedrosian Isabelle 
Published: July 2021

Abstract
Introduction: Cholesterol biosynthesis pathway is highly regulated and inhibition of the pathway with statins is known to cause restorative upregulation of several genes in the pathway. The goal of this study is to investigate if the statin mediated upregulation in the cholesterol biosynthesis pathway genes associates with the resistance to fluvastatin in a model of hormonally insensitive breast cancer
Methods: A published gene signature of statin resistance was validated 1) a cell line based model of breast cancer progression consisting of inherently fluvastatin sensitive and inherently fluvastatin resistant cell lines and also compared to our experimentally derived acquired signature of fluvastatin resistance using 2) an isogenic set of cell lines consisting of a fluvastatin sensitive cell line (MCF10.AT1), and an acquired resistant cell line (MCF10.AT- R) and lastly validated using 3) SV40 C3 tag, a mouse model of hormone receptor negative breast cancer. Clariom RNA profiling were processed and mined by IPA analysis to identify the fluvastatin resistance signature that were validated by qPCR. Fluvastatin resistance was determined in vitro by colony formation assay and in vivo in a mouse model of breast cancer.
Results: We found more than 75% of the published 17 gene panel fluvastatin resistance gene signature (consisting of cholesterol biosynthesis pathway genes) to be significantly upregulated in an inherently resistant cell line, DCIS cell line, relative to fluvastatin sensitive preneoplastic, MCF10.AT1 cell line. We found this inherent statin resistance gene signature to be also relevant in the MCF10.AT-R resistant cells as we found 13 of these genes to map to top 3 upregulated pathways that are steroid biosynthesis, steroid hormone biosynthesis and terpenoid backbone biosynthesis pathway. Next, we tested if 17 gene statin resistance signature associates with presence of tumors in the mammary glands of fluvastatin treated mice and found upregulation of more than 50% of the genes in the resistance signature in the tumor bearing mammary glands. Lastly, we studied if a 10-day period of fluvastatin treatment to SV40C3 Tag mice, a spontaneous mouse model of breast cancer, can also trigger the upregulation of these cholesterol biosynthesis pathway genes and provide an early signal of statin resistance. These experiments showed that a 10-day period is not long enough to cause a feedback upregulation in steroid biosynthesis pathway genes and thus can't be used a surrogate timepoint to detect resistance to fluvastatin.
Conclusions: Upregulation of multiple steroid biosynthesis pathway genes after fluvastatin treatment suggests an opportunity of dual targeting of the cholesterol biosynthesis pathway in order to sensitize the fluvastatin resistant breast cancer cells.
Citation Format: Anjana Bhardwaj, Zhenlin Ju, Matthew Embury, Jing Wang, Isabelle Bedrosian. Gene signature of fluvastatin resistance for prevention of breast cancer and predicting resistance to statins [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2589.