Biology subjects

Rheinheimer, B.

Publications and source records attributed to Rheinheimer, B..

4 recordsLinked to original sources

bioRxiv2020

Inhibition of Sphingosine-1-Phosphate signaling in pancreatic ductal adenocarcinoma leads to downregulation of growth and invasion

BackgroundDeregulated phosphorylation of sphingosine by the sphingosine kinases and signaling through the EDG family of receptors enhances growth and survival in many cell types. Therefore, we sought to elucidate the effect of alterations in the ceramide/sphingosine/S1P rheostat on driving human pancreatic ductal adenocarcinoma towards a malignant phenotype. MethodsPancreatic cancer cell lines were treated with exogenous S1P, FTY720, and siRNA to Sphk1. Migration was evaluated by wound healing assays, cell growth by MTT assays, and invasion by tumorsphere assays. Expression of S1PR1, S1PR3, Sphk1, and Sphk2 were measured by quantitative PCR, western blot, and immunohistochemistry. ResultsS1PR1, S1PR3, and Sphk2 were overexpressed in all pancreatic cancer cell lines. Sphk1 translocated from the cytoplasm to the nucleus in cells located at the leading edge of cell clusters. Exogenous S1P increased cell migration while treatment with FTY720 and Sphk1 siRNA decreased cell growth and invasion. ConclusionsOur results suggest that increased S1PR1 expression may be an early event in pancreatic cancer pathogenesis. Additionally, altered Sphk1 localization may provide a mechanism through which pancreatic ductal adenocarcinoma cells at the leading edge invade into the surrounding matrix. Finally, inhibition of sphingosine-1-phosphate signaling may provide a novel therapeutic target for patients with metastatic disease.

cancer biology↗

bioRxiv2020

Transcriptional regulation of SLIT2 expression in pancreatic cancer cell lines

BackgroundSLIT2 has been shown to serve as a tumor suppressor in breast, lung, colon, and liver cancers. Additionally, expression of SLIT2 has been shown to be epigenetically regulated in prostate cancer. Therefore, we sought to determine transcriptional regulation of SLIT2 in pancreatic ductal adenocarcinoma. MethodsRNA expression of SLIT2, SLIT3, and ROBO1 was examined in a panel of pancreatic ductal adenocarcinoma cell lines while protein expression of ROBO1 and SLIT2 was examined in tumor tissue. Methylation of the SLIT2 promoter was determined using Sequenom while histone modifications were queried by chromatin immunoprecipitation. Reexpression of SLIT2 was tested by treatment with 5-aza-2deoxycytidine and Trichostatin A. ResultsPancreatic cancer cell lines fall into three distinct groups based on SLIT2 and ROBO1 expression. The SLIT2 promoter is methylated in pancreatic ductal adenocarcinoma and SLIT2 expression is dependent on the level of methylation at specific CpG sites. Treatment with 5-aza-2deoxycytidine (but not Trichostatin A) led to SLIT2 reexpression. The SLIT2 promoter is bivalent in pancreatic ductal adenocarcinoma and histone marks around the transcriptional start site are responsible for transcription. ConclusionsLoss of SLIT2 expression modulated by epigenetic silencing may play a role in pancreatic ductal adenocarcinoma progression.

cancer biology↗

bioRxiv2020

Identification and transcriptional regulation of the mir-218-1 alternative promoter

BackgroundmiRNAs are small, endogenous non-coding RNAs approximately 22 nucleotides in length that account for approximately 1% of the genome and play key regulatory roles in multiple signaling pathways. mir-218-1 is an intronic miRNA located within intron 15 of the SLIT2 gene. Public datasets showed enrichment of H3K4me3 within intron 4 of the SLIT2 gene. Therefore, we sought to determine the genomic location and transcriptional regulatory elements of the mir-218-1 candidate alternative promoter in pancreatic ductal adenocarcinoma. MethodsExpression of mir-218 was evaluated in a panel of pancreatic ductal adenocarcinoma cell lines. The mir-218-1 candidate alternative promoter was characterized by chromatin immunoprecipitation, Sequenom, and luciferase assays. Transcriptional regulation of the mir-218-1 candidate alternative promoter was assessed using chromatin immunoprecipitation and an inhibitor to NF-kB. ResultsWe found that expression of mir-218-1 does not correlate with SLIT2 expression and that mir-218-1 has a novel transcriptional start site separate from the SLIT2 promoter. This novel transcriptional start site showed transcriptional activity and was regulated by NF-kB. Conclusionsmir-218-1 is transcribed from an independent and novel transcriptional start site located within intron 4 of the SLIT2 gene in pancreatic ductal adenocarcinoma. Additionally, mir-218-1 expression is regulated by Nf-kB at this alternative transcriptional start site in pancreatic cancer.

cancer biology↗

bioRxiv2020

mir-218 modulates ARF6 expression and inhibits pancreatic ductal adenocarcinoma invasion

BackgroundPancreatic ductal adenocarcinoma is an extremely malignant disease with the majority of patients having metastatic disease upon diagnosis. Recently, it was shown the SLIT2 plays a regulatory role in melanoma invasion through the control of invadopodia. Therefore, we sought to determine the mechanism behind miR-218 inhibition of pancreatic cancer invasion. Methodsmir-218 target genes were discovered using three miRNA target prediction websites. Modulation of mir-218 target ARF6 was determined by transfection with antagomirs and mimics to mir-218. Pancreatic cancer migration and invasion were measured using Boyden chamber assays. Invasion was further measured using matrix degradation assays. ResultsWe found that mir-218 modulates ARF6 RNA and protein expression in pancreatic cancer. mir-218 did not inhibit pancreatic cancer cell migration, but did inhibit invasion. mir-218 did not affect the formation of invadopodia in pancreatic cancer cells, but did inhibit the total area of matrix degradation caused by functional invadopodia. ConclusionsThis work suggests that miR-218 is a suppressor of pancreatic ductal adenocarcinoma invasion through a pathway that regulates invadopodia maturation.

cancer biology↗