ORIGINAL ARTICLE

Genetic evolution of fetoprotein producing gastric cancer

H Fujii¹, K Ichikawa², T Takagaki¹, Y Nakanishi³, M Ikegami⁴, S Hirose¹ and T Shimoda³

¹ Juntendo University School of Medicine, 2-1-1, Hongo, Bunkyo-ko, Tokyo, 113-8421, Japan
² Department of Pathology, Dokkyo University School of Medicine, Tochigi, Japan
³ Pathology Division, National Cancer Centre Research Institute and Hospital, Tokyo, Japan
⁴ Jikei University School of Medicine, Tokyo, Japan

Correspondence to:
Correspondence to:
Dr H Fujii
Department of Pathology II, Juntendo University School of Medicine, 2-1-1, Hongo, Bunkyo-ku, Tokyo 113-8421, Japan, hfujii{at}med.juntendo.ac.jp

Background: Fetoprotein (AFP) producing gastric cancer is an unusual form of aggressive adenocarcinoma with a complex histological picture, including enteroblastic and hepatoid differentiation.

Aims: To investigate the genetic events underlying the phenotypic diversity in AFP producing gastric cancer and the ability of these tumours to produce AFP ectopically.

Methods: Multiple foci from 19 AFP producing gastric adenocarcinomas were microdissected and loss of heterozygosity (LOH) analysis was performed with a panel of microsatellite markers on nine chromosomal arms.

Results: For informative cases, LOH was most frequently detected on 17p (100%), followed by 13q (88%), 3p (87%), 5q and 9p (80%), 11q (70%), 18q (58%), 16q (53%), and 8p (50%). The average fractional allelic loss was 0.72. LOH was detected either homogeneously throughout the microdissected foci, or only in some parts of the neoplastic foci for each case. Heterogeneous patterns of LOH indicated genetic progression and/or divergence in clonal evolution. Furthermore, in six cases with heterogeneous LOH of 13q, 13q LOH was restricted to immunohistochemically AFP positive neoplastic foci.

Conclusion: AFP-GC arises as an aggressive clone with extensive LOH and high fractional allelic loss. The presence of heterogeneous patterns of LOH suggested that the AFP producing carcinoma foci might evolve through genetic progression and/or genetic divergence. Silencing of the crucial gene on 13q may be involved in the acquisition of the AFP producing phenotype.

Keywords: fetoprotein; gastric cancer; loss of heterozygosity; genetics

Abbreviations: AFP, fetoprotein; AFP-GC, fetoprotein producing gastric cancer; FAL, fractional allelic loss; LOH, loss of heterozygosity; HCC, hepatocellular carcinoma; H&E, haematoxylin and eosin; HI, heterogeneity index; PCR, polymerase chain reaction

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