Esophageal squamous cell carcinomas with DNA replication errors (RER+) are associated with p16/pRb loss and wild-type p53.
OBJECTIVE
Microsatellite instability (MSI) as a determinant of propensity to esophageal squamous cell carcinoma (ESCC) at seven microsatellite markers at 2p (2p15-16), 3p (3p13, 3p14.1-3, 3p25, and 3p26) and 16q (16q12.1-3) was investigated to analyze their putative role as indicators of predisposition to esophageal malignancies.


METHODS
Seven microsatellite loci were amplified by polymerase chain reaction, from surgically resected tumor tissues from 30 ESCC patients from Indian population, to assess the loss of heterozygosity (LOH) and replication error repeats (RER) and to correlate these alterations with aberrations in major cell cycle regulatory proteins and histopathological parameters.


RESULTS
LOH and RER analyses at these loci demonstrated moderate microsatellite alterations, suggesting the involvement of MSI in esophageal tumorigenesis in a subset of the Indian population. MSI, defined as RER in at least two or more of the loci studied, was observed in ten of 30 (33%) patients. Twenty-two of 30 patients (73%) showed LOH at one or more loci, while 17 of the 30 patients (60%) showed RER in at least one of the loci studied. RER-positive patients showed a trend towards better prognosis when compared to RER-negative patients. MSI demonstrated a significant association with concomitant loss of p16 and pRb (p16-/pRb- phenotype) (P=0.046). Interestingly, we observed an inverse correlation between MSI and p53 mutations (P=0.03) suggesting that MSI may provide a p53-independent pathway for esophageal tumorigenesis in RER+ patients. MSI showed a trend towards longer survival and absence of distant organ metastasis (P=0.06).


CONCLUSIONS
The present study demonstrates the probable role of MSI in esophageal squamous cell carcinoma in the Indian population. Instability associated with the repetitive sequences--the revealing marks of loss of DNA replication fidelity may serve as an indicator of predisposition to esophageal cancer.
Mathew
R
R
Department of Biochemistry, All India Institute of Medical Sciences, Ansari Nagar, New Delhi.
Arora
S
S
Mathur
M
M
Chattopadhyay
T K
TK
Ralhan
R
R
D002294:Carcinoma, Squamous Cell / Q000235:genetics*; D002874:Chromosome Mapping; D002882:Chromosomes, Human, Pair 13; D002889:Chromosomes, Human, Pair 2; D002893:Chromosomes, Human, Pair 3; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics*; D004261:DNA Replication; D004938:Esophageal Neoplasms / Q000235:genetics*; D005819:Genetic Markers; D006801:Humans; D019656:Loss of Heterozygosity; D018895:Microsatellite Repeats; D019853:O(6)-Methylguanine-DNA Methyltransferase; D016160:Retinoblastoma Protein / Q000235:genetics*
D019941:Cyclin-Dependent Kinase Inhibitor p16; D005819:Genetic Markers; D016160:Retinoblastoma Protein; D019853:O(6)-Methylguanine-DNA Methyltransferase