SERPINB5 and AKAP12-- Expression and promoter methylation of metastasis suppressor genes in pancreatic ductal adenocarcinoma

Abstract

BackgroundEarly metastasis and infiltration are survival limiting characteristics of pancreatic ductal adenocarcinoma (PDAC). Thus, PDAC is likely to harbor alterations in metastasis suppressor genes that may provide novel diagnostic and therapeutic opportunities. This study investigates a panel of metastasis suppressor genes in correlation to PDAC phenotype and examines promoter methylation for regulatory influence on metastasis suppressor gene expression and for its potential as a diagnostic tool.MethodsMetastatic and invasive potential of 16 PDAC cell lines were quantified in an orthotopic mouse model and mRNA expression of 11 metastasis suppressor genes determined by quantitative RT-PCR. Analysis for promoter methylation was performed using methylation specific PCR and bisulfite sequencing PCR. Protein expression was determined by Western blot.ResultsIn general, higher metastasis suppressor gene mRNA expression was not consistent with less aggressive phenotypes of PDAC. Instead, mRNA overexpression of several metastasis suppressor genes was found in PDAC cell lines vs. normal pancreatic RNA. Of the investigated metastasis suppressor genes, only higher AKAP12 mRNA expression was correlated with decreased metastasis (P < 0.05) and invasion scores (P < 0.01) while higher SERPINB5 mRNA expression was correlated with increased metastasis scores (P < 0.05). Both genes' promoters showed methylation, but only increased SERPINB5 methylation was associated with loss of mRNA and protein expression (P < 0.05). SERPINB5 methylation was also directly correlated to decreased metastasis scores (P < 0.05).ConclusionsAKAP12 mRNA expression was correlated to attenuated invasive and metastatic potential and may be associated with less aggressive phenotypes of PDAC while no such evidence was obtained for the remaining metastasis suppressor genes. Increased SERPINB5 mRNA expression was correlated to increased metastasis and mRNA expression was regulated by methylation. Thus, SERPINB5 methylation was directly correlated to metastasis scores and may provide a diagnostic tool for PDAC.

Emerging Roles for SSeCKS/Gravin/AKAP12 in the Control of Cell Proliferation, Cancer Malignancy, and Barriergenesis

“…Thus, although AKAP12 expression is high in many tissues, the loss its expression in transgenic mice results in hyperplasia and/or dysplasia in only some sites (21). Similarly, this may be why AKAP12 downregulation plays a direct role in metastasis suppression in specific tumor sites such as the prostate or pancreas (116). …”

Prognostic Impact of Novel Molecular Subtypes of Small Intestinal Neuroendocrine Tumor

“…LAMA3 hypermethylation has not previously been described in NETs but is a feature of gastric adenocarcinoma, prostate cancer, and breast cancer, and in the case of breast and prostate cancers, hypermethylation of the gene is associated with poorer clinical outcomes (29)(30)(31). SERPINB5 has been described as a "metastasis suppressor gene," and hypermethylation of this gene is associated with metastatic potential in pancreatic adenocarcinoma and poorer clinical outcomes in breast cancer (32,33). Methylation of SERPINB5 in NETs has previously been demonstrated by Verdugo and colleagues; however, determination of hypermethylation compared with normal tissue was not performed (34).…”

Suppression of tumor and metastasis progression through the scaffolding functions of SSeCKS/Gravin/AKAP12

“…The Src-induced downregulation of both α and β AKAP12 promoters involves cis- acting sequences proximal to the transcription start site that bind USF1, Sp1, Sp3, HDAC1 [27], plus a form of TFII-I that converts to a transcriptional repressor once tyrosine phosphorylated by activated Src [28]. Once downregulated, the AKAP12 promoter undergoes hypermethylation at promoter CpG islands in many cancer types such as colon, gastric, prostate, lung, pancreatic and skin [29–37], although a recent case of AKAP12 silencing in multiple myeloma by changes in histone acetylation has been reported [38]. …”

“…For example, AKAP12 silencing via promoter hypermethylation [39, 40] has been shown to function as a neoplastic biomarker in the progression of Barrett’s esophagus to esophageal adenocarcinoma [41]. AKAP12 loss correlates with increased cancer incidence in breast cancer [42, 43], hepatocellular carcinoma [44] and chronic myeloid leukemia [45], and increased lung metastasis in cases of pancreatic cancer [37]. …”