The Pseudokinase TRIB3 Negatively Regulates the HER2 Receptor Pathway and Is a Biomarker of Good Prognosis in Luminal Breast Cancer

Abstract

Background: Tribbles pseudokinase 3 (TRIB3) has been proposed to both promote and restrict cancer generation and progression. However, the precise mechanisms that determine this dual role of TRIB3 in cancer remain to be understood. In this study we aimed to investigate the role of TRIB3 in luminal breast cancer, the most frequent subtype of this malignancy. Methods: We genetically manipulated TRIB3 expression in a panel of luminal breast cancer cell lines and analyzed its impact on cell proliferation, and the phosphorylation, levels, or subcellular localization of TRIB3 and other protein regulators of key signaling pathways in luminal breast cancer. We also analyzed TRIB3 protein expression in samples from luminal breast cancer patients and performed bioinformatic analyses in public datasets. Results: TRIB3 enhanced the proliferation and AKT phosphorylation in luminal A (HER2-) but decreased them in luminal B (HER2+) breast cancer cell lines. TRIB3 negatively regulated the stability of HER2 in luminal B breast cancer cell lines. TRIB3 expression was associated with increased disease-free survival and a better response to therapy in luminal breast cancer patients. Conclusions: Our findings support the exploration of TRIB3 as a potential biomarker and therapeutic target in luminal breast cancer.

Comprehensive Profiling of Mammalian Tribbles Interactomes Implicates TRIB3 in Gene Repression

“…Importantly, long-term overexpression of TRIB3 was recently linked to increased proliferation in MCF7 cells [ 62 ], which potentially confounds interactome profiles, but no significant effects on cell proliferation were observed within the 24-h timeframe of our experiments (data not shown). A summary of top 20 interactors for TRIB1 and TRIB3 ( Figure 3 D) is listed in Table 5 .…”

“…Having developed a robust AP–MS workflow to identify the interaction partners of Tribbles proteins, we wished to address the different roles of TRIB1 and TRIB3 in breast cancer, where high levels of both proteins have been reported to be associated with poor prognosis and lower survival rates [ 26 , 61 , 62 ]. For this we generated inducible TRIB1-tGFP and TRIB3-tGFP stable cell lines in the breast cancer cell line MCF7, a model for luminal A breast cancer, allowing immediate short-term overexpression of TRIB1 and -3, as well as control over the amount of protein being overexpressed.…”

“…These interactions, together with others described above, might suggest a role of Tribbles in DNA damage. Furthermore, whether for example the TRIB3–CDKN1 interaction contributes to the increased proliferation observed upon long-term overexpression of TRIB3 in MCF7 cells [ 62 ] remains to be established.…”

The Pseudokinase TRIB1 in Immune Cells and Associated Disorders

“…The cellular localization of TRIB1 has been reported as both the nucleus and cytoplasm [ 15 , 77 , 90 , 91 ]. Even with the same cell lines, different subcellular localizations were observed suggesting that cellular environment impacts TRIB1 localization.…”

“…Even with the same cell lines, different subcellular localizations were observed suggesting that cellular environment impacts TRIB1 localization. For example, while TRIB1 was found equally distributed between the nuclear and cytosolic fractions by Western blot in MCF7 and BT474 breast cancer cell lines [ 90 ], TRIB1 was mainly found in the cytoplasm of MCF7 cells in a recent report using confocal microscopy [ 76 ].…”