Questions: In breast cancer, cancer cells have progesterone receptors on their surface that bind to progesterone released by the cancer cell themselves. This is an example of signaling. autocrine paracrine endocrine exocrine

The answer is the first one: autocrine signaling.

Explanation for each option:

1. Autocrine signaling: This is when a cell produces a signal to which it itself responds. In the context of the question, breast cancer cells release progesterone, which then binds to progesterone receptors on the same cancer cells. This is a classic example of autocrine signaling.

2. Paracrine signaling: This involves signaling where the target cells are nearby but not the same cell that releases the signal. Since the question specifies that the cancer cells themselves have the receptors for the progesterone they release, this is not paracrine signaling.

3. Endocrine signaling: This involves hormones being released into the bloodstream to affect distant cells. The question describes a local interaction where the cancer cells affect themselves, not distant cells, so this is not endocrine signaling.

4. Exocrine signaling: This involves the release of substances through ducts to the outside of the body or into a body cavity. The question does not describe such a process, so this is not exocrine signaling.

In summary, the interaction described in the question is an example of autocrine signaling, where the cancer cells respond to signals they themselves produce.