Allelic imbalance and microsatellite instability in chromosomes 2p, 3p, 5q, and 18q in esophageal squamous carcinoma in patients from South Africa

Microsatellite polymerase chain reaction (PCR) and fluorescent DNA technolo gy was used to assess allelic imbalance (AI) or loss of heterozygosity (LOH ) and microsatellite instability (MSI) in chromosomes 2p, 3p, 5q, and 18q i n esophagectomy specimens from 39 patients who had squamous carcinoma and w ho lived in a high-incidence geographic location in South Africa. The squam ous carcinomas were graded by conventional light microscopy and staged usin g the tumor-node-metastasis (TNM)-Union Internationale Contre Le Cancer (UI CC) criteria. The DNA was isolated using proteinase K digestion and standar d phenol-chloroform extraction procedure. Microsatellite PCR was performed using fluorescent, CY5-labeled primers for the following markers: (3p), D5S 346 (5q), DCC (18q), D18S34 (18q), and D18S58 (18q). These markers were cho sen because they are the most frequently used and most informative markers for these particular gene loci. Results were analyzed using software attach ed to an automated DNA sequencer. Molecular changes obtained wale correlate d with clinicopathologic parameters. Molecular analysis did not correlate w ith clinicopathologic features, such as tumor grade, stage, or lymph node s tatus. No correlation with patient outcome was seen, though only limited fo llow-ups were obtained. Rates of MSI and LOH on 3p and 18q in these specime ns are similar to the range seen in studies from other geographic areas. Ho wever, a striking point of departure is the high LOH (30% of informative ca ses) seen on 2p.