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Spermidine/spermine N1-acetyltransferase (SSAT) activity in human small-cell lung carcinoma cells following
Tracy Murray-Stewart1, Nancy B Applegren, Wendy Devereux
1Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Bunting Blaustein Building, Room 551, 1650 Orleans Street, Baltimore, MD 21231, USA.
Abstract:
Spermidine/spermine N (1)-acetyltransferase (SSAT) activity is typically highly inducible in non-small-cell lung carcinomas in response to treatment with anti-tumour polyamine analogues, and this induction is associated with subsequent cell death. In contrast, cells of the small-cell lung carcinoma (SCLC) phenotype generally do not respond to these compounds with an increase in SSAT activity, and usually are only moderately affected with respect to growth. The goal of the present study was to produce an SSAT-overexpressing SCLC cell line to further investigate the role of SSAT in response to these anti-tumour analogues. To accomplish this, NCI-H82 SCLC cells were stably transfected with plasmids containing either the SSAT genomic sequence or the corresponding cDNA sequence. Individual clones were selected based on their ability to show induced SSAT activity in response to exposure to a polyamine analogue, and an increase in the steady-state SSAT mRNA level. Cells transfected with the genomic sequence exhibited a significant increase in basal SSAT mRNA expression, as well as enhanced SSAT activity, intracellular polyamine pool depletion and growth inhibition following treatment with the analogue N (1), N (11)-bis(ethyl)norspermine. Cells containing the transfected cDNA also exhibited an increase in the basal SSAT mRNA level, but remained phenotypically similar to vector control cells with respect to their response to analogue exposure. These studies indicate that both the genomic SSAT sequence and polyamine analogue exposure play a role in the transcriptional and post-transcriptional regulation and subsequent induction of SSAT activity in these cells. Furthermore, this is the first production of a cell line capable of SSAT protein induction from a generally unresponsive parent line.
Insights
Researchers created a small-cell lung carcinoma (SCLC) cell line that overexpresses Spermidine/spermine N (1)-acetyltransferase (SSAT). This new SSAT-overexpressing SCLC line shows promise for studying anti-cancer drug responses.
Area of Science:
- Biochemistry
- Molecular Biology
- Oncology
Background:
- Spermidine/spermine N (1)-acetyltransferase (SSAT) activity is inducible in non-small-cell lung cancer, linked to cell death from polyamine analogues.
- Small-cell lung carcinoma (SCLC) cells typically lack SSAT induction and show moderate growth inhibition with these drugs.
Purpose of the Study:
- To develop an SSAT-overexpressing SCLC cell line for investigating SSAT's role in response to anti-cancer polyamine analogues.
- To understand the regulation of SSAT activity in SCLC.
Main Methods:
- NCI-H82 SCLC cells were stably transfected with SSAT genomic or cDNA sequences.
- Clones were selected based on induced SSAT activity and increased SSAT mRNA levels after polyamine analogue exposure.
Main Results:
- Genomic SSAT transfectants showed increased basal SSAT mRNA, enhanced SSAT activity, polyamine depletion, and growth inhibition with N(1),N(11)-bis(ethyl)norspermine.
- cDNA transfectants had increased basal SSAT mRNA but similar responses to controls upon analogue treatment.
- This study successfully generated an SSAT-inducible SCLC cell line from a previously unresponsive parent line.
Conclusions:
- Both the genomic SSAT sequence and polyamine analogue exposure are crucial for SSAT activity regulation in SCLC.
- The newly developed SSAT-overexpressing SCLC cell line is a valuable tool for studying SSAT's function in cancer therapy.
