Numerous genetic and epigenetic changes are involved in tumorigenesis and the progression of various cancers including breast cancer . PIAS3 a modulator of DNA-binding transcription factors was originally identified as a specific inhibitor of the STAT3 signaling pathway which was hyper-activated in various cancers and has been cited in the pathogenesis of breast cancer . Now, it is well recognized that the PIAS family regulates a variety of cytokines and transcription factors with downstream alterations in apoptosis, angiogenesis, and a number of signaling pathways .
PIAS3 gene was shown to be a target of many epigenetic modifications including microRNAs. miRNA-18a was found to be a modulator of STAT3 activity through negative regulation of PIAS3 during gastric adenocarcinogenesis, and it was shown that miRNA-18a suppress their targets in response to different environmental stimuli, which may or may not favor cancer . To clarify the role of PIAS3 and miRNA-18a in breast cancer, we analyzed the expression of PIAS3 mRNA and miRNA-18a in 25 tissue samples of breast cancer (Tumor group) and 25 paired samples of non-cancerous tissue from the same resected breast (Normal group), and they were statistically analyzed along with the clinicopathological data of the studied patients.
In the current work, PIAS3 mRNA expression was significantly downregulated in the tumor group compared to the normal group (p = 0.040). In agreement with this, Chandhoke et al.  revealed that reduction of PIAS3 might be important for the invasive behavior of breast cancer cell-derived organoids via sumoylation of Smurf2, and they suggested that PIAS3 and Smurf2 may serve as biologically relevant biomarkers in human breast cancer. In addition, Yang et al.  found that the total PIAS3 protein decreased in 62% of breast cancer tissues compared with that in the adjacent non-cancerous tissues. Consistently, lower PIAS3 expression has also been observed in various cancers. Liu et al.  revealed that the expression levels of PIAS3 protein and mRNA were significantly lower in gastric cancerous tissues than in its adjacent non-tumor tissues, and also lower in gastric cancer cell lines. Kluge et al.  found that the expression of PIAS3 is variable in lung cancer cell lines with 2 of 3 squamous cell carcinoma cell lines having no or little PIAS3 protein expression, and they found the majority of human small cell carcinoma of the lung lack PIAS3 expression by immunohistochemistry.
On the contrary, McHale et al.  showed a substantial increase in the expression of PIAS3 protein levels in malignant breast tissues as compared to benign/hyperplastic epithelium. In addition, Wang et al.  observed increased PIAS3 expression in 100/103 samples examined in a variety of human cancers including lung, breast, prostate, colon-rectum, and brain tumors.
PIAS proteins act as small ubiquitin-like modifier E3 ligases, and sumoylation of transcription factors can significantly alter their function and their intranuclear localization. By acting as inhibitors of DNA binding, mediators of sumoylation, and/or recruiters of coregulatory proteins, PIAS family members can significantly modify the function of transcription factors that include members of the STAT family, promoting the oncogenic effects of their activation. A previous study showed that PIAS3 overexpression in breast cancer cell lines can significantly modulate STAT5-mediated gene expression and induce cellular apoptosis . In addition, PIAS3 has a vast STAT3-independent effect by binding to a number of transcription factors with downstream alterations in apoptosis, angiogenesis, and a number of signaling pathways, for instance, it interacts with nuclear hormone receptors, androgen receptors, estrogen receptors, p53, BRCA1, and metastasis tumor antigen .
MicroRNAs play a critical role in the carcinogenesis and progression of breast cancer, whereas miRNA-18a has both oncogenic and tumor-suppressive roles . Guo et al.  showed that miRNA-18a was under-expressed in human breast cancer, and thought to have a role as a tumor suppressor. In addition, Krutilina et al.  showed in their animal model that high expression of miRNA-18a had led to decreased spontaneous lung metastasis and tumor growth and increased apoptosis in vitro in response to hypoxic and acidotic conditions, supporting its role as a tumor suppressor.
In contrast, Yoshimoto et al.  showed in their study on 171 breast cancer samples that miRNA-18a was overexpressed in estrogen receptor-negative breast tumors which implicates that it is an oncogene. Also, Mouw et al.  showed that miRNA-18a was upregulated in basal-like breast cancers and its expression correlated with increased future disease aggression for patients with luminal breast cancers identifying miRNA-18a as a mechanically regulated tumor enhancer.
In the present work, miRNA-18a was overexpressed in the tumor group compared to the normal group, but it was not statistically significant (p = 0.861) (Table 2), and this result favored its oncogenic role.
In the present study, miRNA-18a expression was negatively correlated with PIAS3 mRNA expression (r = − 0.469, p = 0.018) (Fig. 3), and this favors that PIAS3 mRNA may be a target to miRNA-18a. Pichiorri et al.  showed that miRNA derived from the miRNA-17–92 cluster including miRNA-18a modulated STAT3 phosphorylation in multiple myeloma cells. In addition, Shuai et al.  found that under physiological conditions, the activation of STAT proteins is rapid and transient because of negative regulation by proteins such as SOCS and PIAS3. Activated STAT3 protects tumor cells from apoptosis and promotes the expression of cell proliferation-associated proteins, such as Bcl-xL, Mcl-1, Bcl-2, Fas, cyclin D1, Survivin, and c-Myc . Wu et al.  speculated that miRNA-18a might target a negative regulator of the STAT3 signaling pathway and determined that the 3′-untranslated region of PIAS3 contains a potential binding site for miRNA-18a and that miRNA-18a could directly target PIAS3 in tumor cell line.
We next examined the association of the expression levels of both PIAS3 mRNA, and miRNA-18a, and the clinicopathological characteristics of the studied patients (Table 3). Only miRNA-18a fold expression was positively correlated with the grade of the tumor (p = 0.029). This was in agreement with Wu et al.  who found that miRNA-18a was highly expressed in high-grade gliomas. Also Blenkiron et al.  revealed that miRNA-18a was overexpressed in grade III tumors. In addition, Motoyama et al.  revealed that miRNA-18a overexpression was associated with poor prognosis in human colorectal cancer. Together, these findings provide a support that miRNA-18a may have a role in tumor proliferation and progression and may be used to develop future biomarkers for prognosis of breast cancer.