Metastasis is the leading cause of mortality in patients with solid tumors. Since there are no clinically- approved targeted therapies for treating triple-negative breast cancer (TNBC), metastatic TNBC pre- sents a dire clinical situation for which intervention strategies are urgently needed. The long-term goal of this proposal is to elucidate novel tumor cell autonomous and non-autonomous mechanisms that drive TNBC progression and metastasis. The overall objective of this proposal is to define the molecu- lar/cellular basis by which post-translational hypusination and nucleocytoplasmic transport of eukaryotic initiation factor 5A (eIF5A1/2) governs pseudopodium-enriched atypical kinase one (PEAK1)-dependent invasion/dissemination and lipocalin two (LCN2)-mediated reprogramming of the premetastatic niche (PMN). Toward this end, evidence is presented that the eIF5A1/2 hypusination/activation pathway associates with poor TNBC prognosis and is required for TGF?/PEAK1-driven metastasis and LCN2 expression in TNBC cells. Furthermore, the eIF5A1/2-LCN2 axis is identified as a novel mechanism through which primary tumor cells remodel the PMN to support TNBC cell expansion. Thus, the central hypothesis of this proposal is that hypusination and cytoplasmic localization of eIF5A1/2 in TNBC cells drives PEAK1-dependent TGF?/fibronectin signaling crosstalk and LCN2-mediated anti-inflammatory reprogramming of the premetastatic niche to support metastasis. The approach is innovative because it represents a substantive departure from the status quo by elucidating targetable eIF5A1/2-dependent translational mechanisms of cell state plasticity at early and late stages in the metastatic cascade using the single-cell Cyclic ImmunoFluorescence (CycIF) platform, our novel in vivo/ex vivo tumor cell-free PMN reprogramming assay, the Multifunctional Approach to Pharmacological Screening (MAPS) platform and a suite of preclinical mouse models that faithfully recapitulate complementary aspects of human TNBC metastasis and progression. Furthermore, the proposed research is significant because it will define spatiotemporal mechanisms by which dysregulation of eIF5A1/2 expression, hypusination and subcellular localization drive TNBC pathogenesis and identify targeted treatment strategies for metastatic TNBC.
Specific Aim 1 will determine cancer cell autonomous mechanisms of eIF5A1/2- mediated TNBC cell invasion and dissemination.
Specific Aim 2 will identify eIF5A1/2-dependent mechanisms of premetastatic niche reprogramming that support TNBC cell seeding and expansion. The collective knowledge gained from these studies will elucidate targetable mechanisms that govern both early and late stages of TNBC metastasis and establish rationale for new therapeutic combina- tions to overcome TNBC progression and improve patient outcomes.
Metastatic triple-negative breast cancer (TNBC) patients have poor clinical outcomes, in part, because there are no targeted therapies approved to treat this aggressive breast cancer subtype. By elucidating new post-translational mechanisms of eIF5A1/2-dependent TGF?/fibronectin-induced heterogeneity and metastasis within primary and premetastatic niches, the proposed studies have the potential to identify new therapeutic strategies for abrogating TNBC progression. Additionally, this work has broad applicability across the field of oncology as many of the molecular regulators being investigated in this proposal have been reported to be altered or dysregulated in other solid tumor types where cancer metastasis is a primary cause of patient mortality.
