Identification of a novel candidate gene, MENC, in a consensus region of allelic deletion at chromosome 10q26 in human endometrial cancer

P Baldinu PhD^a, A Cossu MD^b, A Manca PhD^a, MP Satta, S Tech^a, MC Sini PhD^a, C Rozzo PhD^a, M Pisano PhD^a, M Casula PhD^a, M Colombino PhD^a, PP Demuro PhD^a, G Palomba PhD^a, A Pintus MD^b, A Deiana MD^b, S Dessole MD^c, PL Cherchi MD^c, F Tanda MD^b, G Palmieri MD^a

^aICB-CNR, Alghero, Italy, ^bIstituto di Anatomia Patologica, ^cDipartimento di Ostetricia e Ginecologia; Università di Sassari, Italy

AIM: Loss of heterozygosity (LOH) at 10q25-q26 chromosomal region has been widely reported in endometrial cancer (EC), suggesting the presence of tumor suppressor gene(s) involved in EC pathogenesis. We have identified a minimum consensus region of LOH at 10q25-q26 and here described the molecular analyses performed in order to search candidate gene(s) in this region. METHODS: Microsatellite analysis was performed on paired tumor and normal tissue samples from 146 sardinian EC patients. Bioinformatic approaches allowed to identify ESTs within the candidate region, which were confirmed by both RT-PCR assays and Northern blot hybridization on tissue mRNAs. RACE method was used to further extend the cDNA ends. Germline and somatic DNA from EC patients was used for mutational screening by DHPLC and sequencing analysis. Expression studies by real-time RT-PCR on total RNAs was performed on various paired normal and tumor tissues or cancer cell lines. RESULTS: A 160 kb consensus region of allelic deletion between D10S1236 and WIAF3299 markers was defined at chromosome 10q26. Using a positional candidate approach, we identified three alternative transcripts of a novel human gene, designated MENC (mutated in endometrial cancer); they share the first three exons while they differ in the composition of the downstream ones (MENCa, MENCb, and MENCc). One of such transcripts, MENCa, encodes a short protein of 102 aminoacids with no similarity to any other known gene product. As evidenced by real-time RT-PCR assays, MENCa expression seems to decrease in various tumors as compared to the corresponding normal tissues. Three (7%) MENCa mutations were identified in tumor DNAs from 44 EC patients and in none of the 102 normal controls. One of these mutations is a deletion with a truncation effect on the predicted protein. CONCLUSIONS: Expression of MENCa mRNA seems to be downregulated in several types of cancer (including EC), suggesting that it may act as a potential tumor suppressor gene. The very low mutation rate, taken together with MENCa expression pattern, seems to indicate that inactivation of this putative tumor suppressor gene may occur through epigenetic/regulative modifications. Functional studies on the gene products and, particularly, on the predicted protein could further explain the pathogenic pathway, in which MENC acts, leading to the development of endometrial cancer, or, more in general, to the tumorigenesis.

Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in oral session 896 (Tumor suppressor genes).