Breast cancer is the most common cancer among women and despite advances in therapy over the past few decades, drug resistance, recurrence, metastasis and the heterogeneity of the cancer continue to be a problem in successful management of the diseases(Hong et al ,2019) .~Circular RNAs (CircRNAs) are single-stranded, covalently closed RNA molecules that are ubiquitous across species ranging from viruses to mammals(Zhou et al 3 .,2020). circRNAs can be divided into two categories including coding and noncoding circRNAs(Li et al., 2019) A new subtype of RNAs is circular RNAs, single-strand RNA molecules with less than 100 to more than 4,000 nucleotides (Lu et al., 2016) and a covalently closedloop structure. These molecules are produced through a backsplicing mechanism, in which the downstream 5'-end of the splice donor joins the upstream 3'-end splice acceptor and forms a product with a circular structure (wang et al., 2017).~Chemerin is a leukocyte chemoattractant widely expressed in many tissues and is known to recruit innate leukocytes.~Recently, more and more studies focus on the relationship between chemerin and cancers and found that chemerin acts an essential role in cancers.(Shin et al,2018) Chemerin expression is different depending on the tumor type (Zhang Y et al, 2013) the clinical significance of chemerin in breast cancer has been only reported by a very limited number of studies (EL Sagheer et al,2018).
This study aimed to evaluate the role of serum chemerin as a biomarker of breast cancer.~and To investigate the diagnostic value of hsa_circ_0001785 (Circ-ELP3) and hsa_circ_100219 (Circ-FAF1) in serum samples of breast cancer patients to find out whether these circRNAs can utilize as a diagnostic and prognostic biomarker for human breast cancer assessment and make Correlation between serum chemerin levels , serum Circ-FAF1 , serum CircELP3 and classical tumor markers (CEA + CA15-3).~andTo elucidate if there is a difference between metastatic and non-metastatic cases as regard serum chemerin levels, serum Circ-FAF1 or Circ-ELP3.