Abstract
The expression of TGF-alpha in human colon and lung carcinoma cell lines has been reported previously, but its expression in primary tumours has not been described in detail. We have used the radio-immunoassay method to measure the specific content of immunoreactive TGF-alpha in the acid ethanol extracts of normal and cancerous tissues of human colon and lung. The average TGF-alpha content of colon carcinomas is 4 times that of the normal mucosa, and for non-small cell lung carcinomas it is twice that of the normal parenchyma. Because of variability in the TGF-alpha expression among individuals and in different segments of colon and lobes of lung, the ratio of TGF-alpha content of paired tumour and normal tissue was also calculated. On average, the tumour/normal ratio for colon carcinoma is higher than that for lung carcinoma. Although 55% of colon tumours show a ratio 4 times, or greater, only 33% of lung carcinomas demonstrate this ratio. The level of TGF-alpha in both colon and lung carcinomas does not correlate with histological type stage, grade nor degree of desmoplasia of these tumours. Northern blot analysis of total cellular RNA confirms the expression of an approximately 4.8 kb TGF-alpha mRNA in normal colonic mucosa and lung parenchyma. However, in contrast to the results of radio-immunoassay, significant over-expression of TGF-alpha mRNA is uncommon in primary human colon carcinomas.
Highlights
The amount of immuno-reactive TGF-o in extracts of normal mucosa of colons resected for diverticular disease was not significantly different from that of 'normal' mucosa of cancerous colons
A comparative study indicates that the level of TGF-a mRNA expression in these Discussion colonic tumours or normal mucosa is approximately one hundredth of that expressed by HT-29 colon carcinoma cell
We have further demonstrated the presence of the full-length (4.6-4.8 Kb) TGF-a mRNA species in the total cellular RNA extracts of normal human colonic mucosa, further confirming the expression of this growth factor in normal adult colon
Summary
Human colon and lung carcinoma tissues were obtained within 30 to 60 min after surgical resection. When enough tissue was available, grossly normal colonic mucosa at least 10 cm away from the edge of tumour and the posterior basal segment of the lobectomy specimen from each case was concurrently obtained and used as the paired 'normal/con-. Correspondence: Ming-Sound Tsao, Department of Pathology, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec, Canada H3G 1A4. Received 19 February 1990; and in revised form 9 May 1990. From colons resected for diverticular disease, was obtained. The specimens were snap-frozen in liquid nitrogen and stored at -80'C
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