American Association for Cancer Research
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FIGURE 5 from MARCH2, a Novel Oncogene-regulated SNAIL E3 Ligase, Suppresses Triple-negative Breast Cancer Metastases

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posted on 2024-03-28, 14:20 authored by Koichi Ito, Ibuki Harada, Criseyda Martinez, Katsutoshi Sato, EunJee Lee, Elisa Port, Jessica H. Byerly, Anupma Nayak, Ekta Tripathi, Jun Zhu, Hanna Y. Irie

PTK6 inhibition enhances MARCH2:SNAIL association. A, MDA-MB-231 cells expressing FLAG-Snail and HA-MARCH2 (WT) were treated with vehicle control or P21d for 4 or 18 hours in the presence of MG132. MARCH2–SNAIL interaction was assessed by immunoblotting FLAG immunoprecipitates with anti-HA antibody. B, Endogenous MARCH2–SNAIL interaction following P21d treatment of MDA-MB-231 was assessed by Duolink PLA. Cells were treated with DMSO or P21d for 8 hours and MG132 cotreatment for the last 4 hours. Cells were stained with antibodies to Snail and MARCH2. PLA signals/cell were quantitated using ImageJ (left). Scale bar, 15 µm.


Susan G. Komen (SGK)

American Cancer Society (ACS)

Breast Cancer Research Foundation (BCRF)

New York State Department of Health (NYSDOH)



Epithelial–mesenchymal transition (EMT) in cancer promotes metastasis and chemotherapy resistance. A subset of triple-negative breast cancer (TNBC) exhibits a mesenchymal gene signature that is associated with poor patient outcomes. We previously identified PTK6 tyrosine kinase as an oncogenic driver of EMT in a subset of TNBC. PTK6 induces EMT by stabilizing SNAIL, a key EMT-initiating transcriptional factor. Inhibition of PTK6 activity reverses mesenchymal features of TNBC cells and suppresses their metastases by promoting SNAIL degradation via a novel mechanism. In the current study, we identify membrane-associated RING-CH2 (MARCH2) as a novel PTK6-regulated E3 ligase that promotes the ubiquitination and degradation of SNAIL protein. The MARCH2 RING domain is critical for SNAIL ubiquitination and subsequent degradation. PTK6 inhibition promotes the interaction of MARCH2 with SNAIL. Overexpression of MARCH2 exhibits tumor suppressive properties and phenocopies the effects of SNAIL downregulation and PTK6 inhibition in TNBC cells, such as inhibition of migration, anoikis resistance, and metastasis. Consistent with this, higher levels of MARCH2 expression in breast and other cancers are associated with better prognosis. We have identified MARCH2 as a novel SNAIL E3 ligase that regulates EMT and metastases of mesenchymal TNBC. EMT is a process directly linked to drug resistance and metastasis of cancer cells. We identified MARCH2 as a novel regulator of SNAIL, a key EMT driver, that promotes SNAIL ubiquitination and degradation in TNBC cells. MARCH2 is oncogene regulated and inhibits growth and metastasis of TNBC. These insights could contribute to novel strategies to therapeutically target TNBC.

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