Abstract:
Breast cancer is one of the most common cancers in Pakistan and the leading cause of death among
Pakistani women. The onset of breast cancer in Pakistan occurs earlier as compared to other
countries. Our study investigates the prevalence of ESR1 gene mutations specifically D538G and
novel SNPS including S518N, N519F and N532T in the Pakistani population. Our research aimed
at the detection of D538G and other mutations in formalin-fixed tissue biopsy samples from breast
cancer patients. This study also included identification of SNPs in the ESR1 gene via amplicon
sequencing, in silico structural and functional analysis of SNPs and, in silico drug repurposing
against identified SNPs. In total, 73 samples were collected from collaborative hospitals and
categorized into wild-type and Invasive Ductal Carcinoma. DNA extraction, quantification, PCR
were performed after sequencing and annotation from Macrogen. in silico tools such as PolyPhen,
SNPS & GO, PANTHER, Align GVGD and Phyre2 were used to predict the deleterious effect of
the detected mutation. Our findings showed the presence of ESR1 mutations in the Ligand Binding
Domain of ESR1 including the D538G, S518N, N519F and N532T. The prevalence of the D538G mutation
was seen significantly in middle-aged women. Through in silico analysis, these mutations were identified
as deleterious leading to endocrine resistance in breast cancer and thus failure of current therapies.
Moreover, the drug repurposing identified potential drugs that could target the mutated receptors to offer
alternative treatment options for breast cancer. Thus, the research signifies the role of mutations in the
ligand-binding domain of ESR1 gene leading to endocrine resistance in breast cancer patients. The study
provides a basis for conducting in vitro and in vivo research, and for conducting epidemiological
investigations that can help in overcoming endocrine resistance in the patients of breast cancer
