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Laboratory science
Allelic imbalance at 13q31 is associated with reduced GPC6 in Chinese with sporadic retinoblastoma
  1. Charles S L Lau1,
  2. Christopher B O Yu1,
  3. H K Wong2,
  4. Dorothy S P Fan1,
  5. H T Mak1,
  6. K W Wong1,
  7. Dennis S C Lam1,
  8. Chi Pui Pang1,
  9. Kwong Wai Choy2
  1. 1Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong SAR
  2. 2Department of Obstetrics & Gynaecology, The Chinese University of Hong Kong, Shatin, Hong Kong SAR
  1. Correspondence to Dr Kwong Wai Choy, Department of Obstetrics & Gynaecology, The Chinese University of Hong Kong, 1E, Prince of Wales Hospital, Shatin, Hong Kong SAR; richardchoy{at}


Background/aims Loss of heterozygosity (LOH) has been discovered in retinoblastoma (RB) in previous studies. In this study, we aimed to discover potential tumour suppressor genes through investigation of the incidence of allelic loss in chromosome 1, 6, 9, 13, 19, 20, 21, 22 and X in Chinese sporadic retinoblastoma patients and to study the expression of genes flanking LOH region 13q31.

Methods Twenty-five microdissected RB samples were analysed to investigate the LOH in 140 microsatellite markers. Expression of genes flanking D13S265 was investigated by real-time quantitative-PCR on available frozen samples. The promoter and entire coding region of GPC6 were examined for sequence changes in an extended batch of 29 RB samples.

Results Allele losses were found in 92% (23/25) of the tumours. We identified a new LOH locus at 13q31 (D13S265) with a high occurrence rate (67%, 14/21) apart from the RB1 locus (68%, 17/25). Expression study detected the reduced expression of Glypican 6 (GPC6) transcript significantly associated with the LOH at 13q31 (p=0.024). Furthermore, mutation screening revealed no remarkable sequence alteration in GPC6 that could affect its expression.

Conclusion Results suggest that a reduction in GPC6 mRNA in retinoblastoma is associated with the non-random allelic loss at 13q31 that could contribute to RB development.

  • Retinoblastoma
  • LOH
  • RB1, 13q31
  • genetics
  • neoplasia
  • experimental and laboratory

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  • Funding The work described in this paper was supported in part by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No CUHK 4091/01M) and Action for Vision Research Foundation.

  • Competing interests None.

  • Ethics approval Ethics approval was provided by the Ethic Committee for human research, the Chinese University of Hong Kong.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.