SUMMARY
Background. Triple-negative breast cancers (TNBCs) present with advanced histological grade and
aggressive clinical behavior. They are overwhelmingly unresponsive to conventional systemic treatments, and
patients with refractory disease have increased recurrence and dismal 5-year survival rates. Reliable
biomarkers and targeted therapies for TNBC are therefore critically needed, but remain to be defined.
Preliminary findings. We found that PTX3 was particularly abundant in TNBC specimens and in patient-
derived xenografts (PDX), and that its levels positively and specifically correlated with adverse TNBC patient
survival. We show that PTX3 propagated cancer-stem-cell (CSC) -like traits, that it promoted cancer cell
growth in suspension, and that it promoted multifold increase in TNBC metastasis. In addition, we demonstrate
that PTX3 activated anti-apoptotic pathways and de-sensitized TNBC cells to chemotherapy. Genetic
suppression of PTX3 inhibited oncogene-induced cell growth, and quelled malignant features of TNBC cells,
such as migration and anchorage-independent growth. Importantly, we show that circulating levels of PTX3,
which is secreted by TNBC cells, associated with tumor burden in preclinical models and were particularly
elevated in TNBC patients. Finally, we show that antibody neutralization of PTX3 caused TNBC cell death.
Hypotheses. We hypothesize that PTX3 is a critical biomarker for risk stratification of TNBC patients, and
that it is a decisive functional driver of malignancy and a tractable therapeutic target of translational utility in
TNBC management.
Specific aims and study design. We will establish PTX3 as a prognostic biomarker in clinical TNBC (aim
1), determine how PTX3 regulates malignant progression (aim 2), and establish PTX3 as a TNBC therapeutic
target (aim 3). To this end, we will correlate tumoral and circulating levels of PTX3 to patient survival in
retrospective analyses of a large TNBC patient cohort using PCR-, -in situ, and ELISA-based approaches
(aims 1.1 and 1.2). We will then determine the role of PTX3 in regulating self-renewal and tumor-initiating
functions of CSCs (aim 2.1), identify the metastatic steps facilitated by PTX3 (aim 2.2) and assess its
contributions to chemoresistance in vitro and in vivo (aim 2.3). Finally, we will determine the essentiality of
PTX3 to the initiation (aim 3.1), survival, and growth of established metastases (aim 3.2) using xenograft
models, as well as investigate the ability of anti-PTX3 neutralizing antibodies to suppress tumorigenic growth
using patient-derived xenograft and syngeneic murine cancer models (aim 3.3).
Impact. Our sought results will introduce novel theranostics of potential groundbreaking utility in managing
aggressive and difficult-to-treat breast cancers for which targeted therapies are sorely needed.