leupeptins and Triple-Negative-Breast-Neoplasms

The aryl hydrocarbon receptor (AHR) is a ligand-activated signaling molecule expressed in many cell types, including triple-negative and non-triple-negative breast cancer cells. It affects breast cancer growth and crosstalk with estrogen receptor signaling. Normally, this receptor is degraded shortly after ligand activation via the 26S proteasome. Here, we report that AHR undergoes chaperone-mediated autophagy in MDA-MB-468 triple-negative breast cancer cells. This lysosomal degradation of AHR exhibits the following characteristics: (1) it is triggered by 6 amino-nicotinamide, starvation, and piperazinylpyrimidine compound Q18; (2) it is not observed in non-triple-negative breast cancer cells (MCF-7, T47D, and MDA-MB-361); (3) it can be inhibited by progesterone receptor B but not estrogen receptor alpha; (4) it can be reversed by chloroquine but not MG132; (5) it requires LAMP2A; and (6) it involves AHR-HSC70 and AHR-LAMP2A interactions. The NEKFF sequence localized at amino acid 558 of human AHR appears to be a KFERQ-like motif of chaperone-mediated autophagy, responsible for the LAMP2A-mediated AHR protein degradation.

Topics: Amino Acid Sequence; Basic Helix-Loop-Helix Transcription Factors; Cell Line, Tumor; Chaperone-Mediated Autophagy; Chloroquine; Cytochrome P-450 CYP1A1; Estrogen Receptor alpha; Humans; Leupeptins; Lysosomal-Associated Membrane Protein 2; Lysosomes; MCF-7 Cells; Proteolysis; Receptors, Aryl Hydrocarbon; Receptors, Progesterone; RNA Interference; Signal Transduction; Triple Negative Breast Neoplasms

Tumour metastasis, the spread of cancer cells from the original tumour site followed by growth of secondary tumours at distant organs, is the primary cause of cancer-related deaths and remains poorly understood. Here we demonstrate that inhibition of CDK4/6 blocks breast tumour metastasis in the triple-negative breast cancer model, without affecting tumour growth. Mechanistically, we identify a deubiquitinase, DUB3, as a target of CDK4/6; CDK4/6-mediated activation of DUB3 is essential to deubiquitinate and stabilize SNAIL1, a key factor promoting epithelial-mesenchymal transition and breast cancer metastasis. Overall, our study establishes the CDK4/6-DUB3 axis as an important regulatory mechanism of breast cancer metastasis and provides a rationale for potential therapeutic interventions in the treatment of breast cancer metastasis.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Cell Movement; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinase 6; Disease Models, Animal; Endopeptidases; Female; Gene Expression Regulation, Neoplastic; Humans; Leupeptins; Liver Neoplasms; Lung Neoplasms; MCF-7 Cells; Mice; Ovarian Neoplasms; Piperazines; Pyridines; RNA, Small Interfering; Signal Transduction; Snail Family Transcription Factors; Triple Negative Breast Neoplasms; Xenograft Model Antitumor Assays