title: Aptamer-Assisted Detection of the Altered Expression of Estrogen Receptor Alpha in Human Breast Cancer.
abstract: An increase in the expression of estrogen receptors (ER) and the expanded population of ER-positive cells are two common phenotypes of breast cancer. Detection of the aberrantly expressed ERα in breast cancer is carried out using ERα-antibodies and radiolabelled ligands to make decisions about cancer treatment and targeted therapy. Capitalizing on the beneficial advantages of aptamer over the conventional antibody or radiolabelled ligand, we have identified a DNA aptamer that selectively binds and facilitates the detection of ERα in human breast cancer tissue sections. The aptamer is identified using the high throughput sequencing assisted SELEX screening. Biophysical characterization confirms the binding and formation of a thermodynamically stable complex between the identified DNA aptamer (ERaptD4) and ERα (Ka = 1.55±0.298×108 M(-1); ΔH = 4.32×104±801.1 cal/mol; ΔS = -108 cal/mol/deg). Interestingly, the specificity measurements suggest that the ERaptD4 internalizes into ERα-positive breast cancer cells in a target-selective manner and localizes specifically in the nuclear region. To harness these characteristics of ERaptD4 for detection of ERα expression in breast cancer samples, we performed the aptamer-assisted histochemical analysis of ERα in tissue samples from breast cancer patients. The results were validated by performing the immunohistochemistry on same samples with an ERα-antibody. We found that the two methods agree strongly in assay output (kappa value = 0.930, p-value <0.05 for strong ERα positive and the ERα negative samples; kappa value = 0.823, p-value <0.05 for the weak/moderate ER+ve samples, n = 20). Further, the aptamer stain the ERα-positive cells in breast tissues without cross-reacting to ERα-deficient fibroblasts, adipocytes, or the inflammatory cells. Our results demonstrate a significant consistency in the aptamer-assisted detection of ERα in strong ERα positive, moderate ERα positive and ERα negative breast cancer tissues. We anticipate that the ERaptD4 aptamer targeting ERα may potentially be used for an efficient grading of ERα expression in cancer tissues.
authors.affiliation: Department of System and Chemical Biology, CSIR-Institute of Genomics and Integrative Biology, Delhi, India.|Academy of Scientific and Innovative research, CSIR- Institute of Genomics and Integrative Biology, Delhi, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Ahirwar
authors.affiliation: Department of System and Chemical Biology, CSIR-Institute of Genomics and Integrative Biology, Delhi, India.|Academy of Scientific and Innovative research, CSIR- Institute of Genomics and Integrative Biology, Delhi, India.
authors.forename: Shamsudheen Karuthedath
authors.initials: SK
authors.lastname: Vellarikkal
authors.affiliation: Department of Biosciences and Bioengineering, Indian Institute of Technology, Guwahati, India.
authors.forename: Arghya
authors.initials: A
authors.lastname: Sett
authors.affiliation: Department of System and Chemical Biology, CSIR-Institute of Genomics and Integrative Biology, Delhi, India.|Academy of Scientific and Innovative research, CSIR- Institute of Genomics and Integrative Biology, Delhi, India.
authors.forename: Sridhar
authors.initials: S
authors.lastname: Sivasubbu
authors.affiliation: Department of System and Chemical Biology, CSIR-Institute of Genomics and Integrative Biology, Delhi, India.|Academy of Scientific and Innovative research, CSIR- Institute of Genomics and Integrative Biology, Delhi, India.
authors.forename: Vinod
authors.initials: V
authors.lastname: Scaria
authors.affiliation: Department of Biosciences and Bioengineering, Indian Institute of Technology, Guwahati, India.
authors.forename: Utpal
authors.initials: U
authors.lastname: Bora
authors.affiliation: Dr. Bhubaneswar Barooah Cancer Institute, Guwahati, Assam, India.
authors.forename: Bibhuti Bhusan
authors.initials: BB
authors.lastname: Borthakur
authors.affiliation: Dr. Bhubaneswar Barooah Cancer Institute, Guwahati, Assam, India.
authors.forename: Amal Chandra
authors.initials: AC
authors.lastname: Kataki
authors.affiliation: Dr. Bhubaneswar Barooah Cancer Institute, Guwahati, Assam, India.
authors.forename: Jagannath Dev
authors.initials: JD
authors.lastname: Sharma
authors.affiliation: Department of System and Chemical Biology, CSIR-Institute of Genomics and Integrative Biology, Delhi, India.|Academy of Scientific and Innovative research, CSIR- Institute of Genomics and Integrative Biology, Delhi, India.
authors.forename: Pradip
authors.initials: P
authors.lastname: Nahar
mesh_terms: D052157:Aptamers, Nucleotide / Q000235:genetics / Q000378:metabolism; D001943:Breast Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism; D047628:Estrogen Receptor alpha / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D057166:High-Throughput Screening Assays; D006801:Humans; D007150:Immunohistochemistry; D011980:Receptors, Progesterone / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D052156:SELEX Aptamer Technique; D012680:Sensitivity and Specificity
chemical_list: D052157:Aptamers, Nucleotide; C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D011980:Receptors, Progesterone