Polyclonal nature of diffuse proliferation of interstitial cells of Cajal in patients with familial and multiple gastrointestinal stromal tumours

Abstract

Background: Diffuse proliferation of interstitial cells of Cajal (ICCs) in the myenteric plexus layer of the intestine has been described in patients with familial and multiple gastrointestinal stromal tumours (GISTs). However, it is not fully understood whether proliferation is polyclonal or monoclonal.

Aims: To evaluate the clonal nature of diffuse ICC proliferation in familial and multiple GIST cases, we carried out clonal analysis using inactivation at the human androgen receptor (HUMARA) locus.

Materials and methods: Diffuse ICC proliferation tissues from three female patients were microdissected using a laser capture microdissection (LCM) system. Normal intestinal mucosal tissues were also microdissected for polyclonal controls and GIST tissues for monoclonal controls from the same patients, and genomic DNA was extracted. After digestion by restriction enzyme HhaI, the HUMARA locus was amplified by a fluorescent polymerase chain reaction (PCR) procedure and the PCR products were analysed.

Results: One case was uninformative because it was homozygous at the HUMARA locus. In the two other cases, PCR products from the diffuse ICC proliferation showed two alleles as well as those from normal intestinal mucosal tissues, indicating that ICC proliferation was polyclonal. In contrast, PCR products from associated GIST tissues showed only one allele, indicating that GISTs were monoclonal.

Conclusion: The results suggested that diffuse ICC proliferation in familial and multiple GIST cases was non-neoplastic hyperplasia.

Figure 1

Tissues were microdissected using a laser capture microdissection system from normal intestinal mucosa ((A) before microdissection, (B) after microdissection), diffuse interstitial cells of Cajal proliferation ((C) before microdissection, (D) after microdissection), and gastrointestinal stromal tumours ((E) before microdissection, (F) after microdissection). Representative figures are shown.

Figure 2

Clonal analysis was carried out using undigested and digested DNA from normal mucosa, diffuse interstitial cells of Cajal (ICC) proliferation, and gastrointestinal stromal tumours (GISTs). In case No 1, all of the polymerase chain reaction (PCR) products of undigested (A1) and digested (A2) DNA from normal intestinal mucosa, digested DNA from diffuse ICC proliferation (A3), and GIST (A4) showed only one major peak with an allelic size of 246 bases, indicating that it was uninformative. In case No 2, the PCR product of digested DNA from normal intestinal mucosa (B1) and diffuse ICC proliferation (B2) showed two major peaks with allelic sizes of 231 and 246 bases, while that of digested DNA derived either from a small GIST (B3) or from a large GIST (B4) showed only one allele with a lower molecular weight (allelic size of 231 bases). In case No 3, the PCR product of digested DNA from normal intestinal mucosa (C1) and diffuse ICC proliferation (C2) showed two major peaks with allelic sizes of 240 and 252 bases, and that of digested DNA from a large GIST showed one allele with a lower molecular weight (allelic size of 240 bases) (C3), while that of digested DNA from a small GIST demonstrated the other allele with higher molecular weight (allelic size of 252 bases) (C4).