Hormone Receptor Status Of Breast Cancers

Breast cancer is diagnosed at a level of about 100,000-120,000 new cases per year in the United States, and 40,000 die each year from this most common cause of cancer in women. For some time breast cancers have been classified on the basis of receptor measurements from biopsy specimens. Thus, in general, these cancers fall into three categories: estrogen receptor (ER) positive and progesterone receptor (PR) positive; ER positive and PR negative; and ER negative and PR negative. These measurements show that in those cancers with normal levels of ER and PR the cells should be responsive to the growth-stimulating effects of estrogen. Furthermore, the positive expression of PR indicates that the ER is functional in that PR is a pheno-typic product of ER action. Such tumors are more amenable to treatment and therapy with antiestrogens and other maneuvers. The progression of tumor status from hormone dependent to hormone independent (ER-, PR-) is a bad sign, and a hormone-independent tumor is virtually impossible to control. A similar situation is obtained in prostatic cancer with regard to the hormone (dihydrotestosterone) dependence of the tumor for growth. As long as these tumors are hormone dependent, they can be treated with estrogen inhibitors (tamoxifen) in the case of mammary cancer or with androgen inhibitors in the case of prostatic cancer. Some ideas concerning the actions of estrogen and tamoxifen on ER-positive breast cancer cells are shown in Figure 20-5. As was mentioned before, tamoxifen is also being used in prostatic cancer and is probably effective due to its ability to inhibit the production of

Autocrine Growth Factors

TGF-cx

|STIMULATES|

Autocrine Growth Factors

TGF-cx

|STIMULATES|

52 kDa Protein

Plasminogen-Activator

35-39 kDa Protein

52 kDa Protein

Plasminogen-Activator

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