Abstract A81: A microRNA signature identified for chemoresistance and mesenchymal phenotype is also found in advanced pancreatic cancer

Recent studies link cancer cells that possess an epithelial to mesenchymal transition (EMT) and cancer stem cell properties with chemoresistance and metastatic potential. Here, we investigated the molecular bases of the chemoresistant mesenchymal phenotype (CRMP) with emphasis on identifying a micro-RNA (miRNA) signature in advanced pancreatic ductal adenocarcinoma (PDAC). We developed a gemcitabine resistant cell model from a PDAC cell line, BxPC3. This gemcitabine resistant cell line (BxPC3-GZR) showed a pronounced mesenchymal phenotype and expressed high levels of CD44 a marker found on stem cells and showed a highly significant increase in expression of nine miRNAs and decrease in eight miRNAs. Based on relevance to cancer and on validation by q-RT-PCR we chose six of the miRNAs (miR-100, miR-125b, miR-21, miR-205, miR-27b and miR-455-3p) as a signature to determine whether they were similarly deregulated in 43 advanced PDAC tumor specimens previously analyzed as part of the Total Cancer Genome Atlas (TCGA). A strong correlation was observed for five of the six miRNAs in the tumor specimens compared to normal pancreas tissue.

To assess the functional relevance we initially focused on miRNA-125b, which is over-expressed in both cellular CRMP and advanced PDAC. Knockdown of miRNA-125b in BxPC3-GZR and Panc-1 cells caused a partial reversal of the mesenchymal phenotype and enhanced response to gemcitabine. Moreover, RNA-seq data from each of 40 advanced PDAC tumor specimens from the TCGA data base indicate a negative correlation between expression of miRNA-125b and five of six potential target genes (BAP1, BBC3, NEU1, BCL2, STARD13). Thus far, two of these target genes, BBC3 and NEU1, that are tumor suppressor genes but not yet studied in PDAC, appear to be functional targets of miR-125b since knockdown of miR125b caused their up regulation. The results of this study suggests that CRMP is caused in part by deregulation of a specific set of miRNAs and that these miRNAs are also deregulated in advanced PDAC. These miRNAs and their molecular targets may serve as targets to enhance sensitivity to chemotherapy and reduce metastatic spread.

Citation Format: James W. Freeman, Alakesh Bera, Venkatasubbarao Kolaparthi. A microRNA signature identified for chemoresistance and mesenchymal phenotype is also found in advanced pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A81.

Targeted therapy of human osteosarcoma with 17AAG or rapamycin: characterization of induced apoptosis and inhibition of mTOR and Akt/MAPK/Wnt pathways

Osteosarcoma is highly resistant to current chemotherapy regimens. Novel therapeutic approaches, potentially involving targeting of specific survival pathways, are needed. We used 17-AAG to inhibit Hsp90 and rapamycin to inhibit mTOR, in the osteosarcoma cell lines, HOS and KHOS/NP. HOS and KHOS cells were treated for 24 and 48 h with 17-AAG or rapamycin and studied drug-induced apoptosis, cell cycle, mitochondrial membrane potential and levels of reduced glutathione (GSH), dephosphorylation of signal transduction proteins in the Akt/MAP kinase pathway and mTOR signaling. 17-AAG was a potent inducer of apoptosis, involving effective depletion of GSH and mitochondrial membrane (MM) depolarization, strong activation of caspase-8 and -9 and release of AIF from mitochondria to the cytosol. Furthermore, 17-AAG down-regulated pAkt, p44Erk, p-mTOR, p70S6, TSC1/2 and pGSK-3beta. Treatment with 17-AAG also caused down-regulation of cyclin D1, GADD45a, GADD34 and pCdc2 and upregulation of cyclin B1 and mitotic block. A decrease in Hsp90 and increase in Hsp70 and Hsp70 C-terminal fragments were also observed. Rapamycin was a less potent inducer of apoptosis, involving a small decrease in GSH and MM potential with no activation of caspases or release of AIF. Rapamycin strongly inhibited cell growth with an increase in G1 and a decrease in S-phase of the cell cycle concomitant with down-regulation of cyclin D1. Rapamycin also down-regulated the activity of p70S6, pAkt and p-mTOR, but had no effect on pGSK-3beta, p44Erk, pCdc2, TSC1/2 or Hsp70 or Hsp90. We conclude that Hsp90 inhibition merits further study in the therapy of osteosarcoma.