Molecular Profile of Human Serine Palmitoyltransferase-1 Proximate of Chromosome 9 Disease Susceptibility Gene Cluster in Inflammatory Cancer Cell Lines

Abstract

Background: Over 1100 genes have been annotated for human chromosome 9, including disease genes implicated in inflammation, atherosclerosis, cancer and neurodegeneration. The serine palmitoyltransferase-1, SPTLC1, gene is at the 9q22.2 cytogenetic band, a high G+C content region with common genetic alterations sufficient to modify cellular behavior. The sequence is highly conserved among diverse species from bacteria to humans, including a recently discovered 126 nucleotide alternate open reading frame, AltORF. The protein encoded by the reading frames has domains of biological interest and considerable overlapping molecular functions associated with cellular behavior and cancer progression. Methods: Here we examined molecular features of SPTLC1 in a group of inflammation associated cancer cell lines SKN-SH, MDA-PCa, Glioma LN18, PC3 and 647V. Subcellular localization of SPTLC1 was assessed by immunofluorescence microscopy and recombinant green fluorescent protein expression. In addition, PCR, DNA sequencing and bioinformatics analysis were used for molecular profiling of the SPTLC1 genomic and reverse transcribed cDNA fragments. Results: SPTLC1 is detected in all cell lines examined, with intense peri-nuclear staining, consistent with localization in the cytoplasm. Genomic DNA sample, but not the cD NA of SKN cells could be amplified with an AltORF primer set. The PC3 and MDA-PCa cancer cell lines which are both of prostate origin, show differences in SPTLC1 PCR amplification. Similar levels of SPTLC1 AltORF transcripts were detected by quantitative RT-PCR in all cell lines, except the PC3 cell line with low transcript level whose cDNA did not generate nucleotide base sequence information. Conclusions: This is the first reported transcriptional expression of the SPTLC1 AltORF for the inflammation associated human cancer cell lines. Interestingly, it is proximate of oncogenic cancer susceptibility genes and distal of tumor suppressor genes, the high content of short nucleotide repeats in the SPTLC1 AltORF sequence suggesting the region may be genetically unstable. This nominal functional genomics report on the human SPTLC1 AltORF will contribute to compiling a more detailed SPTLC1 gene ontology and is expected to help shed more insight into unique molecular attributes of SPTLC1 in the context of cancer cell behavior, malignant progression and the design of treatment for inflammation associated cancers.