- Email: [email protected]
MORE ABOUT HUMAN ONCOGENES
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linked to changes in the histological appearance of chronic hepatitis than are the results of conventional tests. In none of these reports, however, was the correlation between serum bile acid levels and histological findings so close that liver biopsy could be deemed unnecessary. Rather than a marker of disease, serum bile acid levels may be of more value in ruling it out; thus, where Gilbert’s syndrome is suspected because of lone unconjugated hyperbilirubinaemia, the finding of normal serum bile acid levels would make that diagnosis more certain. 50 In screening for liver disease serum bile acid levels are perhaps more sensitive than any other individual blood test, but probably not more so than the standard combination of liver tests offered by most laboratories. The assay systems for serum bile acid measurement do not lend themselves to auto-analysis. In view of the questionable clinical relevance of an extra, albeit more sensitive and specific, liver function test, measurement of serum bile-acid levels is likely to remain a research tool, or at least be restricted to centres with a special interest.
MORE ABOUT HUMAN ONCOGENES
ONCOGENES-specific segments of DNA which confer the properties of malignancy’ -have now been isolated from several human cancer cell lines. There is fierce competition to be the first to determine a precise mechanism for human cancer, and progress has been remarkable. Two separate groups have now found the difference between a human
bladder-cancer oncogene and its corresponding normal gene.2,3 The result is amazingly simple: the swapping (transversion) of a base pair from guanosine-cytosine to adenine-thymine at a defined position in the gene. Over the past two years several groups have isolated pieces of human DNA with oncogenic potential by means of the transfection assay. Here pieces of DNA are precipitated with calcium phosphate and mixed with an indicator cell line such as NIH 3T3, a non-transformed mouse fibroblast. Oncogenic DNA changes the growth pattern of the cells from a confluent monolayer into clumps of piled up, transformed fibroblasts. These cells now grow as tumours in mice whereas the NIH 3T3 cells do not. The beauty of this technique is that the oncogenic DNA can come from any species including man. By cloning of genes in suitable plasmid or bacteriophage vectors, unlimited quantities of defined pieces of DNA can be produced. The combination of gene cloning and the transfection assay provides a powerful tool by which human cancer genes can be isolated and analysed. In the newly reported experiments from the United States, DNA was prepared from two human bladder-carcinoma lines, EJ and T24. Restriction enzymes were used to JM, Berk PD, Hofmann AF, Martin JF, Wolkoff AW, Scharschmidt BF. fasting-state levels of serum cholyl conjugated bile acids in Gilbert’s syndrome: an aid to the diagnosis Hepatology 1982; 2: 340-43.
50. Vierling
Normal
1. Editorial. Human oncogenes Lancet 1982; ii: 195-96. 2. Tobin CT, Bradley SM, Borgmann CI, Weinberg RA, Papageorge AG, Scolnick EM, Dhor R, Lowry DR, Chang EG. Mechanism of activation ofa human oncogene. Nature 1982; 300: 143-49. 3. Reddy EP, Reynolds RK, Santos E, Barbacid M A point mutation is responsible for the acquisition of transforming properties by the T24 human bladder carcinoma oncogenes Nature 1982; 300: 149-52. 4. Weinberg RA. Use of transfection to analyse genetic information and malignant transformation Biochem Biophys Act 1981, 651: 25-35.
fragment the DNA, and the smallest piece with oncogenic potential in a transfection assay was immortalised by gene cloning. This turned out to be a sequence of 6600 nucleotide base pairs. The sequence showed remarkable homology to an RNA tumour virus oncogene (v-Ha-ras) which causes in rats.s The oncogene codes for a 21 000 dalton protein, p21. The cloned human oncogene was then compared with the corresponding DNA sequence isolated from normal bladder epithelium. By breaking and recombination of these two DNA sequences the site of the difference was identified and the DNA sequence determined. A single base-pair transversion was noted at position 35 in the functional p21 gene. Such a transversion causes the twelth aminoacid of p2l to be changed from glycine to valine. Several key questions are outstanding. How does p21 result in the alteration of a cell’s growth-control apparatus to cause malignant change? How universal is the mechanism involved? Perhaps most important of all is, how can this discovery be harnessed to reverse the changes of malignancy in patients? Biopsy material from patients with common solid tumours often contains DNA sequences related to the oncogenes of RNA tumour viruses, suggesting that these intriguing results are not artifacts of cell lines but provide a promising new avenue of research in clinical oncology. There are vast sums of money available to fund clinical cancer research but a dearth of new ideas. The time has come to group young clinicians able and willing to grasp the impact of modern molecular biology with energetic scientists in order to bring these developments to the bedside of the cancer sarcomas
patient as soon as possible. TOPICAL DILEMMAS IN ACNE TREATMENT THE mainstay in management of moderate or severe acne is long-term, low-dose antibiotic therapy with either erythromycin or one of the original tetracyclines such as tetracycline or oxytetracycline. Most patients so treated will respond well, but for maximum benefit the treatment must be continued for at least six months.6 In patients who do not respond the dose of the original antibiotic can be increased from the usual 0 - 5 g daily to 1 or even 2 g daily in severe cases, or the oral antibiotic can be changed to co-trimoxazole, minocycline, or clindamycin. Oral clindamycin is particularly effective in acne but when taken orally it occasionally causes antibiotic-associated colitis. What about the possibility of treating acne, and in particular minor degrees of acne, with topical antibiotics? Topical preparations of tetracycline, clindamycin, and erythromycin are all available in the United States and have been approved by the Food and Drugs Administration;but many dermatologists believe that topical antibiotics are generally less effective than conventional oral treatment.’ Three papers by Cunliffe and his co-workers 8-10 raise important points about topical application of antibiotics in 5. Prodha LF, Tobin CJ, Shih C, Weinberg RA. Human EJ bladder carcinoma oncogene is homologue of Harvey sarcoma virus rat gene. Nature 1982; 297: 474-78. 6. Cunliffe WJ, Clayden AD, Gould D, Simpson MB. Acne vulgaris—its aetiology and treatment. A review. Clin Exp Dermatol 1981, 6: 461-69. 7. Stoughton RB. Topical antibiotics for acne vulgaris. Current uses. Arch Dermatol 1979; 115: 486-89. 8. Eady EA, Holland KT, Cunliffe WJ. The use of antibiotics in acne therapy oral or topical administration? J Antimicrob Chemother 1982; 10: 89-115. 9. Eady EA, Holland KT, Cunliffe WJ. Topical antibiotics in acne therapy.J Am Acad Dermatol 1981; 5: 455-56. 10. Eady EA, Holland KT, Cunliffe WJ. Should topical antibiotics be used for the treatment of acne vulgaris? Br J Dermatol 1982; 107: 235-46
linked to changes in the histological appearance of chronic hepatitis than are the results of conventional tests. In none of these reports, however, was the correlation between serum bile acid levels and histological findings so close that liver biopsy could be deemed unnecessary. Rather than a marker of disease, serum bile acid levels may be of more value in ruling it out; thus, where Gilbert’s syndrome is suspected because of lone unconjugated hyperbilirubinaemia, the finding of normal serum bile acid levels would make that diagnosis more certain. 50 In screening for liver disease serum bile acid levels are perhaps more sensitive than any other individual blood test, but probably not more so than the standard combination of liver tests offered by most laboratories. The assay systems for serum bile acid measurement do not lend themselves to auto-analysis. In view of the questionable clinical relevance of an extra, albeit more sensitive and specific, liver function test, measurement of serum bile-acid levels is likely to remain a research tool, or at least be restricted to centres with a special interest.
MORE ABOUT HUMAN ONCOGENES
ONCOGENES-specific segments of DNA which confer the properties of malignancy’ -have now been isolated from several human cancer cell lines. There is fierce competition to be the first to determine a precise mechanism for human cancer, and progress has been remarkable. Two separate groups have now found the difference between a human
bladder-cancer oncogene and its corresponding normal gene.2,3 The result is amazingly simple: the swapping (transversion) of a base pair from guanosine-cytosine to adenine-thymine at a defined position in the gene. Over the past two years several groups have isolated pieces of human DNA with oncogenic potential by means of the transfection assay. Here pieces of DNA are precipitated with calcium phosphate and mixed with an indicator cell line such as NIH 3T3, a non-transformed mouse fibroblast. Oncogenic DNA changes the growth pattern of the cells from a confluent monolayer into clumps of piled up, transformed fibroblasts. These cells now grow as tumours in mice whereas the NIH 3T3 cells do not. The beauty of this technique is that the oncogenic DNA can come from any species including man. By cloning of genes in suitable plasmid or bacteriophage vectors, unlimited quantities of defined pieces of DNA can be produced. The combination of gene cloning and the transfection assay provides a powerful tool by which human cancer genes can be isolated and analysed. In the newly reported experiments from the United States, DNA was prepared from two human bladder-carcinoma lines, EJ and T24. Restriction enzymes were used to JM, Berk PD, Hofmann AF, Martin JF, Wolkoff AW, Scharschmidt BF. fasting-state levels of serum cholyl conjugated bile acids in Gilbert’s syndrome: an aid to the diagnosis Hepatology 1982; 2: 340-43.
50. Vierling
Normal
1. Editorial. Human oncogenes Lancet 1982; ii: 195-96. 2. Tobin CT, Bradley SM, Borgmann CI, Weinberg RA, Papageorge AG, Scolnick EM, Dhor R, Lowry DR, Chang EG. Mechanism of activation ofa human oncogene. Nature 1982; 300: 143-49. 3. Reddy EP, Reynolds RK, Santos E, Barbacid M A point mutation is responsible for the acquisition of transforming properties by the T24 human bladder carcinoma oncogenes Nature 1982; 300: 149-52. 4. Weinberg RA. Use of transfection to analyse genetic information and malignant transformation Biochem Biophys Act 1981, 651: 25-35.
fragment the DNA, and the smallest piece with oncogenic potential in a transfection assay was immortalised by gene cloning. This turned out to be a sequence of 6600 nucleotide base pairs. The sequence showed remarkable homology to an RNA tumour virus oncogene (v-Ha-ras) which causes in rats.s The oncogene codes for a 21 000 dalton protein, p21. The cloned human oncogene was then compared with the corresponding DNA sequence isolated from normal bladder epithelium. By breaking and recombination of these two DNA sequences the site of the difference was identified and the DNA sequence determined. A single base-pair transversion was noted at position 35 in the functional p21 gene. Such a transversion causes the twelth aminoacid of p2l to be changed from glycine to valine. Several key questions are outstanding. How does p21 result in the alteration of a cell’s growth-control apparatus to cause malignant change? How universal is the mechanism involved? Perhaps most important of all is, how can this discovery be harnessed to reverse the changes of malignancy in patients? Biopsy material from patients with common solid tumours often contains DNA sequences related to the oncogenes of RNA tumour viruses, suggesting that these intriguing results are not artifacts of cell lines but provide a promising new avenue of research in clinical oncology. There are vast sums of money available to fund clinical cancer research but a dearth of new ideas. The time has come to group young clinicians able and willing to grasp the impact of modern molecular biology with energetic scientists in order to bring these developments to the bedside of the cancer sarcomas
patient as soon as possible. TOPICAL DILEMMAS IN ACNE TREATMENT THE mainstay in management of moderate or severe acne is long-term, low-dose antibiotic therapy with either erythromycin or one of the original tetracyclines such as tetracycline or oxytetracycline. Most patients so treated will respond well, but for maximum benefit the treatment must be continued for at least six months.6 In patients who do not respond the dose of the original antibiotic can be increased from the usual 0 - 5 g daily to 1 or even 2 g daily in severe cases, or the oral antibiotic can be changed to co-trimoxazole, minocycline, or clindamycin. Oral clindamycin is particularly effective in acne but when taken orally it occasionally causes antibiotic-associated colitis. What about the possibility of treating acne, and in particular minor degrees of acne, with topical antibiotics? Topical preparations of tetracycline, clindamycin, and erythromycin are all available in the United States and have been approved by the Food and Drugs Administration;but many dermatologists believe that topical antibiotics are generally less effective than conventional oral treatment.’ Three papers by Cunliffe and his co-workers 8-10 raise important points about topical application of antibiotics in 5. Prodha LF, Tobin CJ, Shih C, Weinberg RA. Human EJ bladder carcinoma oncogene is homologue of Harvey sarcoma virus rat gene. Nature 1982; 297: 474-78. 6. Cunliffe WJ, Clayden AD, Gould D, Simpson MB. Acne vulgaris—its aetiology and treatment. A review. Clin Exp Dermatol 1981, 6: 461-69. 7. Stoughton RB. Topical antibiotics for acne vulgaris. Current uses. Arch Dermatol 1979; 115: 486-89. 8. Eady EA, Holland KT, Cunliffe WJ. The use of antibiotics in acne therapy oral or topical administration? J Antimicrob Chemother 1982; 10: 89-115. 9. Eady EA, Holland KT, Cunliffe WJ. Topical antibiotics in acne therapy.J Am Acad Dermatol 1981; 5: 455-56. 10. Eady EA, Holland KT, Cunliffe WJ. Should topical antibiotics be used for the treatment of acne vulgaris? Br J Dermatol 1982; 107: 235-46