ABSTRACT
The original version of this Article contained an error in Fig. 7. In panel b, the survival curves were shifted relative to the y axis. This error has been corrected in both the PDF and HTML versions of the Article.
ABSTRACT
Elevated MYC expression sensitizes tumor cells to apoptosis but the therapeutic potential of this mechanism remains unclear. We find, in a model of MYC-driven breast cancer, that pharmacological activation of AMPK strongly synergizes with BCL-2/BCL-XL inhibitors to activate apoptosis. We demonstrate the translational potential of an AMPK and BCL-2/BCL-XL co-targeting strategy in ex vivo and in vivo models of MYC-high breast cancer. Metformin combined with navitoclax or venetoclax efficiently inhibited tumor growth, conferred survival benefits and induced tumor infiltration by immune cells. However, withdrawal of the drugs allowed tumor re-growth with presentation of PD-1+/CD8+ T cell infiltrates, suggesting immune escape. A two-step treatment regimen, beginning with neoadjuvant metformin+venetoclax to induce apoptosis and followed by adjuvant metformin+venetoclax+anti-PD-1 treatment to overcome immune escape, led to durable antitumor responses even after drug withdrawal. We demonstrate that pharmacological reactivation of MYC-dependent apoptosis is a powerful antitumor strategy involving both tumor cell depletion and immunosurveillance.
Subject(s)
Antibodies, Monoclonal/pharmacology , Antineoplastic Agents/pharmacology , Apoptosis/drug effects , Genes, myc/drug effects , Immunotherapy , Aniline Compounds/pharmacology , Animals , Antibodies, Monoclonal, Humanized , Apoptosis/immunology , Breast Neoplasms/drug therapy , Breast Neoplasms/pathology , Bridged Bicyclo Compounds, Heterocyclic/pharmacology , CD8-Positive T-Lymphocytes , Cell Line, Tumor/drug effects , Cell Survival/drug effects , Clustered Regularly Interspaced Short Palindromic Repeats , Drug Combinations , Female , HEK293 Cells , Heterografts , Humans , Metformin/pharmacology , Mice , Mice, Transgenic , Proto-Oncogene Proteins c-bcl-2 , Sulfonamides/pharmacology , bcl-X ProteinABSTRACT
Oncogenic transcription factor Myc deregulates the cell cycle and simultaneously reprograms cellular metabolism to meet the biosynthetic and bioenergetic needs of proliferation. Myc also sensitizes cells to mitochondria-dependent apoptosis. Although metabolic reprogramming has been circumstantially connected to vulnerability to apoptosis, the connecting molecular pathways have remained poorly defined. Here, we show that Myc-induced altered glutamine metabolism involves ATP depletion and activation of the energy sensor AMP-activated protein kinase (AMPK), which induces stabilizing phosphorylation of p53 at Ser15. Under influence of Myc, AMPK-stabilized tumor suppressor protein p53 accumulates in the mitochondria and interacts with the protein complex comprised of B-cell lymphoma 2 (Bcl-2) antagonist/killer (BAK) and Bcl2-like 1 (Bcl-xL). Mitochondrial p53 induces conformational activation of proapoptotic Bak without disrupting the Bak-Bcl-xL interaction. Further liberation of Bak specifically from the p53-activated Bak-Bcl-xL complex leads to spontaneous oligomerization of Bak and apoptosis. Thus, Myc-induced metabolic changes are coupled via AMPK and phospho-p53 to the mitochondrial apoptosis effector Bak, demonstrating a cell-intrinsic mechanism to counteract uncontrolled proliferation.
