UNRAVELING MOLECULAR MECHANISMS UNDERLYING MEIS1ONCOGENIC ACTIVITY; POSSIBLE COMPETITION WITH PREP1

Meis1 and Prep1 homeodomain-containing transcription factors are essential for the normal embryonic development of several tissues and organs. Although they both can recruit Pbx at least for some of their biological function using the same homology region, the Meis1-Pbx and Prep1-Pbx complexes bind different DNA sequences and play opposite roles in tumorigenicity. In cancer, Meis1 has been extensively implicated in leukemia and neuroblastoma. Overexpression of Meis1 greatly shortens the latency and affects the penetrance of myeloid leukemia induced by Hox genes retroviral transduction. Furthermore, Meis1 has essential oncogenic function in all human leukemic MLL- translocation. Although, Meis1 is strongly suggested for involvement in human neuroblastoma and glioma, its function in non-hematological malignancies and solid tumors remains poorly defined. In contrast, Prep1 does not accelerate Hox-induced leukemogenesis. In fact heterozygous or homozygous Prep1-deficient mice develop tumors at high frequency. In mice, Prep1 haploinsufficiency causes spontaneous tumor formation and accelerates development of tumors in E\u3bcMyc transgenic mice. In human tumors, PREP1 is absent or downregulated in a large fraction of tumors including lung, breast and colon cancers. Therefore, Prep1 exerts tumor suppressor function in the cell by maintaining genomic stability and hence preventing neoplastic transformation. Here I show that Meis1 is involved in malignant transformation of Prep1-deficient MEFs and that this can be partially rescued by re-expression of Prep1. I demonstrate that the Pbx-interacting domain of Prep1 is involved in its tumor suppressor function. Moreover, Both Meis1 and Prep1 require Pbx1 for their oncogenic and tumorsppressive functions, respectively. Therefore Meis1 and Prep1 do compete for Pbx1 in the context of tumor development. Furthermore, I find Meis1 interacts with Ddx3x and Ddx5 RNA helicases,which is perturbed in the presence of Prep1. Together, the presented results suggest that Meis1 is a bona-fide oncogene also in non-hematic cells and that Prep1 impairs Meis1 tumorigenicity by either competing for Pbx1 or preventing its interaction with transcriptionally relevant partners

Development of a quantitative Real-Time PCR for micrometastasis detection using CEA in peripheral blood and bone marrow specimens of gastric cancer patients

"n Normal 0 false false false EN-US X-NONE AR-SA MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi;} Background: Gastric adenocarsinoma is the first leading fatal malignancy in Iran. Despite advances in novel therapeutics approaches for gastric cancer (GC) patient, tumor dissemination via blood stream to distant organ is still the major cause of death. Therefore, there is urgent need to establish sensitive methods for early detection of disseminated tumor cells in peripheral blood (PB) and bone marrow (BM) specimens of gastric cancer patients. "n"nMethods: In the present study, we use Carcinoma Embryonic Antigen (CEA) as a tumor marker and Glyceraldehyde 3-Phosphate Dehydrogenase (GAPDH) as an internal control to detection and quantification of disseminated tumor cells in PB and BM specimens of affected individuals. Total RNA was extracted from AGS (gastric cancer) cell line and CEA and GAPDH fragments were generated by reverse transcription. The amplified fragments were cloned into pTZ57R/T vector separately. Double cloning of these genes has done into one pTZ57R/T vector. Serial dilution of this recombinant plasmid is used to construct standard curve, each containing a known amount of input copy number. Total RNA was extracted from BP and BM specimens of 35 GC patients. cDNA of the specimens were synthesized by reverse transcription and subjected to Quantitative Real-Time PCR (QRT-PCR)."n"nResults: We developed a highly sensitive and specific quantitative PCR for CEA and GAPDH using Real-Time PCR based on TaqMan technology. CEA mRNA was detected in 23% of PB and 20% of BM specimens. There was no CEA mRNA detecting in control group."n"nConclusions: The QRT-PCR for CEA can be a useful technique for detection of micrometastases in the PB and BM specimens of gastric cancer patients."

Homeodomain transcription factor and tumor suppressor Prep1 is required to maintain genomic stability

Prep1 is a homeodomain transcription factor that is essential in embryonic development and functions in the adult as a tumor suppressor. We show here that Prep1 is involved in maintaining genomic stability and preventing neoplastic transformation. Hypomorphic homozygous Prep1i/i fetal liver cells and mouse embryonic fibroblasts (MEFs) exhibit increased basal DNA damage and normal DNA damage response after γ-irradiation compared with WT. Cytogenetic analysis shows the presence of numerous chromosomal aberrations and aneuploidy in very early-passage Prep1i/i MEFs. In human fibroblasts, acute Prep1 down-regulation by siRNA induces DNA damage response, like in Prep1i/i MEFs, together with an increase in heterochromatin-associated modifications: rapid increase of histone methylation and decreased transcription of satellite DNA. Ectopic expression of Prep1 rescues DNA damage and heterochromatin methylation. Inhibition of Suv39 activity blocks the chromatin but not the DNA damage phenotype. Finally, Prep1 deficiency facilitates cell immortalization, escape from oncogene-induced senescence, and H-RasV12–dependent transformation. Importantly, the latter can be partially rescued by restoration of Prep1 level. The results show that the tumor suppressor role of Prep1 is associated with the maintenance of genomic stability