Breast cancer (BC) is a prevalent malignancy among women, ranking as the second most commonly diagnosed cancer globally. Notably, a substantial proportion of breast cancer-related fatalities, up to 90 percent, are attributed to the development of distant organ metastases. While Cadherin1 (CDH1) has conventionally been considered a tumor-suppressor gene in cancer research, recent investigations have unequivocally revealed that both CDH1 and its encoded E-cadherin exhibit oncogenic characteristics. The primary focus of this case-control study is to ascertain the involvement of the CDH1 gene in a specific subset of Iraqi female patients. A total of ninety patients sought diagnosis and treatment at the Oncology Teaching Hospital in Medical City and the Oncology Unit at Al-Yarmouk Teaching Hospital in Baghdad. In addition, we included 30 apparently healthy individuals as blood control subjects and another 30 women with benign breast tumors as tissue control subjects for the study. In the initial phase of the study, we conducted a serological analysis using enzyme-linked immunosorbent assay (ELISA) to detect the concentration of E-cadherin in serum samples from two groups of BC patients. The group with locally advanced and metastatic BC exhibited a significantly higher E-cadherin concentration (963.4 ± 89.8 pg/mL) compared to the group with localized BC. In the second part of the research, qRT-PCR was performed to analyze the expression of the CDH1 gene across all sample types. CDH1 was shown to have the greatest fold expression (2.550 ± 0.164) in cases with locally progressed and metastatic BC. Compared to the seemingly healthy control group, the fold expression for localized BC was 1.456 ± 0.055, and for malignant tissue it was 1.886 ± 0.08621. In conclusion, this study provides compelling evidence supporting CDH1 as an oncogene in BC. The significance of CDH1 in BC tumorigenesis underscores its potential for the development of novel detection biomarkers and targeted therapeutic approaches for BC treatment. Notably, CDH1 exhibited elevated expression levels in BC tissues and demonstrated an association with an unfavorable distant metastasis-free survival outcome.

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