Transduction of E2F-1 TAT fusion proteins represses expression of hTERT in primary ductal breast carcinoma cell lines.
BACKGROUND
Telomerase expression is detectable in 81-95% of breast carcinomas and may serve as a therapeutic target. The objective of this study was to investigate repression of telomerase activity in primary ductal breast cancer cells through transcriptional regulation of the catalytic subunit hTERT. We hypothesized that inhibition of telomerase expression could be achieved via Tat mediated protein transduction of the repressor protein E2F-1.


METHODS
Protein purification techniques were refined to yield biologically active Tat fusion proteins (TFPs) capable of transducing the breast cancer cell lines HCC1937 and HCC1599. Cell lines were treated with wildtype E2F-1 (E2F-1/TatHA), mutant E2F-1 (E132/TatHA) and a control Tat peptide (TatHA) for 24 hours. Total RNA was isolated from treated cells, reverse transcribed and fold changes in gene expression for hTERT determined via real-time RT-qPCR.


RESULTS
Significant repression of the catalytic subunit of telomerase (hTERT) was present in both HCC1937 and HCC1599 cells following treatment with E2F-1/TatHA. In HCC1937 cells, hTERT was repressed 3.5-fold by E2F-1/TatHA in comparison to E132/TatHA (p < 0.0012) and the TatHA peptide controls (p < 0.0024). In HCC1599 cells, hTERT was also repressed with E2F-1/TatHA treatment by 4.0-fold when compared to the E132/TatHA control (p < 0.0001). A slightly lower hTERT repression of 3.3-fold was observed with E2F-1/TatHA in the HCC1599 cells when compared to the TatHA control (p < 0.0001).


CONCLUSIONS
These results suggest that transduction of E2F-1/TatHA fusion proteins in vitro is an effective repressor of hTERT expression in the primary ductal breast cancer cell lines HCC1937 and HCC1599.
Elliott
Kimberly A
KA
Center for Integrated BioSystems, ADVS Department, Utah State University, Logan, UT 84322-4815, USA. kimberly.elliott22@yahoo.com
Rickords
Lee F
LF
Labrum
J Marcelete
JM
D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D018270:Carcinoma, Ductal, Breast / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D050687:E2F1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D014161:Transduction, Genetic
D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D015696:Gene Products, tat; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D019098:Telomerase