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Sequencing Small Non-coding RNA from Formalin-fixed Tissues and Serum-derived Exosomes from Castration-resistant Prostate Cancer Patients
Published on: November 19, 2019
Reciprocal deregulation of NKX3.1 and AURKA axis in castration-resistant prostate cancer and NEPC models
Moloud Aflaki Sooreshjani1, Mohini Kamra1, Amina Zoubeidi2
1Department of Chemistry and Purdue University Center for Cancer Research, 560 Oval Drive, West Lafayette, IN, 47907, USA.
Background:
NKX3.1, a prostate-specific tumor suppressor, is either genomically lost or its protein levels are severely downregulated, which are invariably associated with poor prognosis in prostate cancer (PCa). Nevertheless, a clear disconnect exists between its mRNA and protein levels, indicating that its post-translational regulation may be critical in maintaining its protein levels. Similarly, AURKA is vastly overexpressed in all stages of prostate cancer (PCa), including castration-resistant PCa (CRPC) and neuroendocrine PCa (NEPC), although its transcripts are only increased in ~ 15% of cases, hinting at additional mechanisms of deregulation. Thus, identifying the upstream regulators that control AURKA and NKX3.1's levels and/or their downstream effectors offer an alternative route to inhibit AURKA and upregulate NKX3.1 in highly fatal CRPC and NEPC. AURKA and NKX3.1 have not linked to each other in any study to date.
Methods:
A chemical genetic screen revealed NKX3.1 as a direct target of AURKA. AURKA-NKX3.1 cross-talk was analyzed using several biochemical techniques in CRPC and NEPC cells.
Results:
We uncovered a reciprocal loop between AURKA and NKX3.1 in CRPC and NEPC cells. We observed that AURKA-mediated NKX3.1 downregulation is a major mechanism that drives CRPC pathogenesis and NEPC differentiation. AURKA phosphorylates NKX3.1 at three sites, which degrades it, but AURKA does not regulate NKX3.1 mRNA levels. NKX3.1 degradation drives highly aggressive oncogenic phenotypes in cells. NKX3.1 also degrades AURKA in a feedback loop. NKX3.1-AURKA loop thus upregulates AKT, ARv7 and Androgen Receptor (AR)-signaling in tandem promoting highly malignant phenotypes. Just as importantly, we observed that NKX3.1 overexpression fully abolished synaptophysin and enolase expression in NEPC cells, uncovering a strong negative relationship between NKX3.1 and neuroendocrine phenotypes, which was further confirmed be measuring neurite outgrowth. While WT-NKX3.1 inhibited neuronal differentiation, 3A-NKX3.1 expression obliterated it.
Conclusions:
NKX3.1 loss could be a major mechanism causing AURKA upregulation in CRPC and NEPC and vice versa. NKX3.1 genomic loss requires gene therapy, nonetheless, targeting AURKA provides a powerful tool to maintain NKX3.1 levels. Conversely, when NKX3.1 upregulation strategy using small molecules comes to fruition, AURKA inhibition should work synergistically due to the reciprocal loop in these highly aggressive incurable diseases.
Insights
A reciprocal loop between AURKA and NKX3.1 drives aggressive prostate cancer. Targeting AURKA can maintain NKX3.1 levels, offering a therapeutic strategy for castration-resistant and neuroendocrine prostate cancer.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- NKX3.1, a prostate tumor suppressor, is lost or downregulated in prostate cancer (PCa), correlating with poor prognosis.
- AURKA is overexpressed in PCa, but transcript levels don't fully explain its upregulation, suggesting post-translational regulation.
- Understanding regulators of NKX3.1 and AURKA offers therapeutic avenues for advanced PCa.
Purpose of the Study:
- To investigate the relationship between AURKA and NKX3.1 in prostate cancer.
- To elucidate the mechanisms driving castration-resistant PCa (CRPC) and neuroendocrine PCa (NEPC).
Main Methods:
- Chemical genetic screen to identify NKX3.1 as an AURKA target.
- Biochemical analyses in CRPC and NEPC cell lines to study AURKA-NKX3.1 cross-talk.
Main Results:
- A reciprocal loop between AURKA and NKX3.1 was identified in CRPC and NEPC cells.
- AURKA phosphorylates and degrades NKX3.1, driving PCa pathogenesis and NEPC differentiation.
- NKX3.1 also degrades AURKA, and this loop upregulates AKT, ARv7, and AR signaling, promoting malignancy.
- NKX3.1 overexpression inhibits neuroendocrine phenotypes.
Conclusions:
- NKX3.1 loss may cause AURKA upregulation, and vice versa, in CRPC and NEPC.
- Targeting AURKA can maintain NKX3.1 levels, while AURKA inhibition may synergize with NKX3.1 upregulation strategies.
- These findings provide insights into therapeutic strategies for aggressive prostate cancer.
