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Clinical Review Science, medicine, and the future

Molecular assessment of cancer

BMJ 1998; 316 doi: (Published 02 May 1998) Cite this as: BMJ 1998;316:1360
  1. Carlos Caldas, senior research associate (
  1. University of Cambridge Department of Oncology, Addenbrooke's Hospital, Box 193, Cambridge CB2 2QQ

    The recent announcement of cancer as the main cause of death in the United Kingdom comes at the end of two decades of exciting advances in understanding the basic biology of human tumours. It is now established that the development of neoplasia is due to accumulated genetic alterations in somatic cells. Identifying cell populations that share specific genetic alterations from samples of saliva, sputum, urine, stool, and blood is likely to be become a routine method of screening populations for common cancers. Genetic assessment will also be used to stage tumours and detect micrometastases. The correlation of specific profiles of genetic alterations with clinical outcome will help define prognosis more accurately and enable clinicians to target treatment more effectively.

    Cancer as a disease of genetic alterations

    The major discovery in cancer biology has been that tumorigenesis is a multistep process associated with accumulated genetic alterations in somatic cells. The progression of a tumour through preneoplasia to frank neoplasia and then invasion and metastasis is the result of successive rounds of clonal expansion of somatic cells that acquire a selective growth advantage as a result of mutations in genes that control cellular proliferation and death.1 Mutations result either in the activation of oncogenes, which promote cellular proliferation or inhibit cell death, or in the inactivation of tumour suppressor genes, which inhibit proliferation or promote cell death. To become a cancer cell, a normal cell needs to accumulate at least five or six of these mutations.1

    Mutations occur at a higher rate in cancer cells because their genetic material (chromosomes or DNA) is intrinsically unstable.1 This genetic instability seems to be a “property” of cancer cells.1

    Colorectal carcinoma is the best studied example of the genetic alterations that underlie human cancer.2 A normal mucosal cell with inactivation of a tumour suppressor gene called APC …

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