Abstract. Annexins are associated with metastasis and infiltration of cancer cells. Proteomic analysis and immunohistochemical staining were used to understand whether several annexins play important roles in cancer alone and/ or synergistically. Seven fresh breast cancer samples with 23 paraffin specimens, three fresh pancreatic samples and five fresh laryngeal carcinoma samples with 25 paraffin specimens were obtained from humans, as well as ten golden hamster pancreatic cancer tissue samples, and they were used to observe differential expression of annexins compared with normal tissues using proteomics and immunohistochemical staining. Annexin A2, A4 and A5 were overexpressed in human breast cancer and laryngeal carcinoma tissues and in golden hamster pancreatic cancer tissue samples, respectively, as shown by proteomics and immunohistochemical staining. In addition, annexin A4 and A5 were expressed in breast cancer tissues, while annexin A1 was not expressed. Annexin A1, A2 and A4 were expressed in human laryngeal carcinoma tissues as shown by immunohistochemical staining. Annexin A1, A2, A4 and A5 played important roles in breast cancer, pancreatic cancer and laryngeal carcinoma, alone and/or synergistically, and they may be targets of therapy for malignant tumors. The choice of which annexins to target should depend on their respective biological behaviors.

S1P binding to S1P5 inhibits the proliferation and migration of S1P5-transfected Eca109 cells. Esophageal cancer cells may down-regulate the expression of S1P5 to escape the inhibitory effect.

Abnormal expression of annexin A2 contributes to metastasis and infiltration of cancer cells. To elucidate the cause of abnormal expression of annexin A2, Western blotting, immunoproteomics and immunohistochemical staining were performed to analyze differentially ubiquitinated proteins between fresh breast cancer tissue and its adjacent normal breast tissue from five female volunteers. We detected an ubiquitinated protein that was up-regulated in the cancer tissue, which was further identified as annexin A2 by mass spectrometry. These results suggest that abnormal ubiquitination and/or degradation of annexin A2 may lead to presence of annexin A2 at high level, which may further promote metastasis and infiltration of the breast cancer cells.

The present study used RNA interference (RNAi) to study how the expression of annexin A2 was affected by ubiquitin protein ligase E3A (UBE3A). In addition, the proliferation, apoptosis and invasiveness of BT-549 breast cancer cells was studied following knockdown of UBE3A. Three pairs of small interfering RNA (siRNA) fragments targeting UBE3A were designed and transfected into the BT-549 cells. The effects of silencing UBE3A were detected by reverse transcription-polymerase chain reaction and western blotting, and the same methods were used to detect the expression levels of annexin A2. Cell proliferation was determined using the Cell Counting kit-8, and flow cytometry and a Transwell chamber assay were used to assess the rate of cell apoptosis and invasion, respectively. Following transfection with the three siRNAs targeting UBE3A for 72 h, the mRNA expression levels of UBE3A were downregulated, as compared with those in the untreated groups, and siRNA1 was the shown to be the most effective siRNA for silencing UBE3A expression. The protein expression levels were concordant with the mRNA expression levels of UBE3A. In addition, the mRNA and protein expression levels of annexin A2 were downregulated. Cellular proliferation and invasion of the siRNA1 group was inhibited as compared with those in the untreated groups, and apoptosis of UBE3A-siRNA1 cells was increased as compared with that in the untreated groups. The results of the present study indicated that UBE3A may regulate the expression of annexin A2, resulting in promotion of proliferation and invasion and suppression of apoptosis in BT-549 cells.