Papillary and follicular thyroid carcinomas show a different pattern of ras oncogene mutation

Abstract

In a small initial study of oncogene activation in differentiated thyroid cancer, using DNA transfection and tumorigenicity assays, we identified activating ras mutations in 80% (4/5) of follicular carcinomas, but in only 20% (2/10) of papillary carcinomas (Lemoine et al., 1988). However, Suarez et al. (1988), using the 'focus' transformation assay, reported two out of a total of three papillary carcinomas to have activated ras oncogenes, while Fusco et al. (1987), also using DNA transfection techniques, failed to find any activating ras mutations in 20 papillary cases analysed. These conflicting results indicated the need for further study of the prevalence of ras mutations in thyroid cancer.We now report a further series of papillary carcinomas, analysed by polymerase chain reaction (PCR) amplification and oligonucleotide probing of archival material, and summarise our data on the incidence and type of mutation in a total of 33 differentiated thyroid carcinomas.Wax-embedded tissue blocks of eight papillary thyroid carcinomas (up to 7 years old) were obtained from the archives of the Department of Pathology, University of Wales College of Medicine. Sections of 5.m were deparaffinised twice with xylene, washed twice with ethanol and vacuum desiccated (Shibata et al., 1988). Dried pellets were mixed with sterile water, denatured for 10 min at 95°C and rapidly cooled to 4'C. PCR incubations were prepared with a Perkin Elmer/Cetus Gene Amp kit according to the manufacturers' protocol. Final concentrations were 10 mM Tris pH 8.3, 50 mM KCI, 1.5 mM MgCl2, 0.2 mM of each dNTP, 1 tIM of each of a pair of amplimers and 2.5 units of Taq DNA polymerase (Saiki et al., 1986). Amplimers were 20 bases long, each pair enclosing an amplified region of 100 bp. Samples received 50 cycles of amplification in a Cetus thermal cycler, with 1 min denaturation at 94°C, 2.5 min annealing at 55'C and 3 min extension at 72°C. A 10 pl aliquot of each incubation was run on a 2.5% agarose gel to check for specific amplification, and reactions were repeated until sharp single bands were obtained.After an initial quantitation, 5-12gdl of each PCR-amplified mixture was diluted to 200 t l I in 1O mM Tris pH 8.0/ 1 mM EDTA, denatured at 95°C for 5 min and cooled rapidly to 4'C. Replicate slotblots, prepared using Hybond-N filters (Amersham) and a Millipore vacuum slotblot apparatus were prehybridised at 56°C for 30 min in 3 M tetramethylammonium chloride (TEMAC)/50 mM Tris pH 7.5/2 mM EDTA/0.3% SDS/5 x Denhardts solution, 100 flg ml-' denatured herring sperm DNA (Wood et al., 1985). Filters were hybridised for 1-2 h at 56°C with 32P-endlabelled 20mer oligonucleotide probes specific for mutations altering aminoacids at the 12, 13, and 61 positions of each of the three human ras genes. As a check on quantitation, filters were first autoradiographed after non-stringent washes in 2 x SSPE/0.1% SDS at room temperature. They were then Correspondence:

c-Ki-ras gene mutations in dysplasia and carcinomas complicating ulcerative colitis

“…Wright et al (1989) found 3/17 (17%) of papillary carcinomas (which classically arise de novo), contained ras mutations compared to 8/15 (53%) of follicular carcinomas which arise through an adenoma-carcinoma sequence; this difference is statistically significant (2 = 4.95 P <0.05). The difference in the prevalence of ras mutations found between carcinomas arising from dysplasia as opposed to origin from adenomas in both colorectal and thyroid tumours may also become apparent in other tumour systems, and suggests that molecular changes may underlie morphological abnormalities.…”

Variability of Ha-ras (codon 12) proto-oncogene mutations in diverse thyroid cancers

“…In papillary carcinomas, Ha-ras codon 12 mutations were found in 4 of 66 (6%) cases. Suarez et al (20) and Du Villard et al (7) found a high frequency of mutations: 50% and 44% of cases respectively, (Table 3), but Wright et al (6) and Manenti et al (13) observed no mutations in these cancers. In eight cases of undifferentiated carcinomas, we detected no point mutation of Ha-ras, in agreement with the findings of Suarez et al (20) and Du Villard et al (7).…”

“…Mutations of the ras (Ha-, Ki-, N-ras) proto-oncogene have been reported in 20-60% of thyroid tumours, particularly in follicular types (3,5,6,15,17), and more frequently in iodine-deficient areas (16). For this reason, ras mutations have been suggested as an important pronostic marker for thyroid cancer (17).…”

“…Studies of various types of benign and malignant thyroid tumours have revealed the presence of activated ras oncogenes in some of them (3)(4)(5)(6)(7). Although the number of tumours included in each study was relatively small, it appears that mutations in ras genes are frequent in thyroid tumours, and can affect all three ras genes.…”

The role of wild-type p53 in the differentiation of primary hemopoietic and muscle cells

“…In myeloid leukemia the chronic phase is characterized by loss of proliferation control but maintenance of di erentiation capacity, while the conversion to the acute, blastic phase is associated with loss of di erentiation capacity (Champlin and Golde, 1985) and, in 50 ± 60% of the cases, mutation in the TP53 gene (Feinstein et al, 1991). In thyroid, the relatively benign, well di erentiated carcinomas do not present TP53 mutations, which are only found in the aggressive, anaplastic forms (Wright et al, 1991, reviewed in Fagin, 1994. Interestingly, a similar correlation has been also found in p53 knock-out mice where chromosomal abnormalities and anaplastic phenotypes are more frequent and severe in p53 7/7 mice than in wild type mice (Kemp et al, 1993;Venkatachalam et al, 1998).…”