Table 1.

Characteristics of the four functional forms of autophagy

Forms of autophagyCharacteristics
Cytoprotectivea. May confer resistance to therapy
b. Increased sensitivity to therapy when blocked
c. Increased apoptosis when blocked
d. Possibly involved in normal tissue homeostasis
Cytotoxica. Promotes cell death when induced
b. Cell death may be associated with subsequent apoptosis
c. Reduced sensitivity to therapy when blocked
d. Unlikely to mediate actions of conventional therapeutic modalities
Cytostatica. Mediates growth inhibition
b. Results in reduced clonogenic survival
c. Potentially associated with senescence
d. Involved in tumor growth delay/dormancy?
Nonprotectivea. Does not differ in intensity from other forms
b. Inhibition does not influence sensitivity to therapy
c. Relevance related to efforts to enhance response to therapy through autophagy inhibition