Objectives: Previously, we demonstrated that the LOT1 (PLAGL1/ZAC1) gene encodes a zinc-finger transcription factor and has growth suppressive effects in carcinoma cell lines. The gene is localized on chromosome 6q24-25, a common site for loss of heterozygosity (LOH) in many solid tumors including ovarian cancer. In this study, we evaluated the LOT1 gene expression and allelic deletion in the tumor tissues in order to provide additional evidence to support the gene's potential role in cancer.
Methods: The LOT1 gene expression was analyzed in malignant ovarian epithelium obtained from frozen human ovarian tumor tissues using laser capture microdissection (LCM) and real-time PCR techniques. Highly frequent single nucleotide polymorphic (SNP) sites within the LOT1 gene were identified and used for PCR and direct sequencing to determine the occurrence of allelic imbalance in a series of surgically resected ovarian and breast carcinomas.
Results: The analysis revealed that LOT1 mRNA expression was not detectable in 12 of 31 (39%) cases of ovarian cancer and was variable between the remaining 19 tumor specimens. These findings are consistent with the previous data that showed altered expression of LOT1 in different human ovarian carcinoma cell lines. In addition, we analyzed the occurrence of LOT1 allelic deletion in different ovarian tumor genomic DNA samples that included papillary serous (majority), mucinous, and primary peritoneal adenocarcinomas of low- to high-grade and the corresponding normal lymphocytes. The informative samples showed 12 out of 33 or about 36.4% LOH of this gene based on allelic loss of one or more polymorphic sites within the LOT1 genomic sequences. Similarly, primary breast carcinomas, which included invasive ductal (majority), spindle cell, mucinous, giant cell, and atypical medullary carcinomas, were examined on genomic DNA from patients for the allelic loss of LOT1. The informative cases showed 4 out of 10 samples or 40% LOH of this candidate tumor suppressor gene locus in breast cancer.
Conclusions: The altered expression and LOH of the LOT1 locus support the gene's potential role, at least in part, in the pathogenesis of ovarian cancer and possibly in other types of cancer.