CancerQuest | Drugs that Affect Molecular Receptors

Our cells constantly monitor their surroundings for the presence (or sometimes an absence) of regulatory molecules in the environment. These signals control decisions regarding cell division, movement and even death. One way in which the external environment is monitored is through receptor molecules located in the membrane of the cell. These proteins act like cellular antennas. Upon binding of a signal molecule, the receptor molecules transmit information to other molecules within the cytoplasm and nucleus resulting in an appropriate response. An example is the HER-2/neu oncogene product, that functions as a growth factor receptor. This gene is discussed more in the section on oncogenes.⁽¹⁾ Many different diseases, including cancer, can be traced back to dysfunctional signaling pathways. In cancer these malfunctions may lead to unregulated cell division and the development of tumors. Particular signaling pathways are often affected in a given type of cancer. Drugs designed to inhibit these specific signaling pathways promise to inhibit cancer growth without harming normal cells. Blockage of the receptors is an active area of clinical investigation. ⁽¹⁾

Specific receptor inhibition remains a relatively new but promising area of medical research. One potential problem with the receptor inhibitors are the long-term side effects of these drugs. The treatments are relatively new so the side effects are also not well described at this time. As a general rule the side effects documented to date are much less severe than conventional chemotherapy treatments.

There are now several drugs that work by binding to cell surface proteins and receptors. The list below is not intended to be exhaustive. We have chosen drugs that interfere with different pathways to provide an overview of the approaches being taken:

Approved Treatments:
Bexarotene (Targretin®)
Denileukin diftitox (ONTAK®)

Additional specific receptor antagonists target hormone receptors located within cells. Information on these inhibitors is located in the Hormonal section of the Cancer Treatments section.
Breast Cancer - Selective Estrogen Receptor Modifiers (SERM's)
Prostate Cancer - Selective Androgen Receptor Modifiers (SARM's)

Drugs that block blood vessel growth are described in the section on angiogenesis inhibitors.