What is the primary action of Tamoxifen in treating metastatic breast carcinoma?

Tamoxifen is classified as a selective estrogen receptor modulator (SERM) and is primarily utilized in the treatment of hormone receptor-positive metastatic breast carcinoma. Its mechanism of action involves competing with estradiol, the primary form of estrogen, for binding sites on estrogen receptors in tissues. This competition effectively inhibits the estrogen receptor's activation, which is critical in promoting the growth and proliferation of certain types of breast cancer cells that are driven by estrogen.

By blocking estradiol's access to its receptors, Tamoxifen can help slow down or halt the growth of tumors that require estrogen for proliferation. This is particularly beneficial in cases where the cancer cells are estrogen receptor-positive, making Tamoxifen a cornerstone treatment option in managing this specific type of breast cancer.

While increasing DNA and RNA synthesis, promoting nucleic acid biosynthesis, or increasing the concentration and response of estrogen may have potential relevance in broader contexts of cell biology, they do not accurately describe the primary pharmacological action of Tamoxifen in this specific therapeutic setting.