Breast Cancer (BC) is the leading cause of cancer-related death in women. Therapy resistance is a major
limiting factor. Therefore, the long-term goal of this grant is to elucidate novel molecular mechanisms
underlying therapy resistance. BC stem cells (CSCs) may mediate treatment resistance in part by altering the
tumor microenvironment (TME) to promote immune evasion. p27 plays a dual role: as a tumor suppressor, it
inhibits cell cycle; and as an oncogene, it promotes metastasis when phosphorylated by PI3K activated
kinases on its C-terminal at T157 and T198 (p27pTpT). p27pTpT acts as a transcriptional regulator of cJun,
driving EMT/pro-metastatic gene profiles. My thesis work showed it also coactivates STAT3 to upregulate
CSCs and cancer promoting-inflammation. My overarching hypothesis is that p27pTpT co-activates STAT3
gene profiles to expand cancer stem cells and promote immune evasion. My thesis work in AIM1.1 made
the novel observation that p27pTpT upregulates stem cell properties including sphere formation and embryonic
stem cell transcription factors (ES-TFs, MYC, OCT4, NANOG, and KLF4), by co-activating STAT3. My ChIP-
seq/RNA-seq showed p27 recruits STAT3 to gene promoters to induce broad profiles of p27/STAT3 co-targets,
including MYC and JAG1, to increase tumor-initiating stem cells (TISC) in vivo. I showed p27pTpT-driven CSC
expansion is in part mediated through the novel p27/STAT3 co-target gene, ANGPTL4. In the F99, AIM1.2,
pursues the hypothesis that p27pTpT/STAT3 promotes tumor immune evasion by re-shaping the TME. I will
expand my research into cancer immunology which provides me with an outstanding training opportunity. My
ATAC-seq showed p27pTpT increases chromatin accessibility to co-recruit p27/STAT3 at promoters of
oncogenic, proinflammatory genes (IL-6, NF-κB (RELA), VEGFA) and the mediator of immune evasion, PDL1.
p27pTpT also increased NF-κB (p65), IL6 proteins and secreted CCL2. Next, I will test if p27pTpT drives
cancer-promoting inflammation and shapes the TME toward a more tumor-permissive state in vivo. First, I will
identify how p27pTpT modulates both tumor cell and immune cell signatures and cytokine expression by single
cell RNA-seq of BC and Luminex assays of cytokines in peripheral blood of tumor bearing mice in vivo. I will
also test how p27pTpT might drive immune evasion by modulating CD4, CD8 T cell and NK cell infiltration in
TME and test if p27pTpT recruits MDSCs, Tregs and increases the M2/M1 macrophage ratio in the TME by
IHC and by flow cytometry. In AIM2, my K00 addresses mechanisms underlying the greater prevalence and
mortality of breast cancer in obese women. My K00 will investigate if p27pTpT promotes the chronic
inflammation of obesity by cooperating with the estrogen receptor (ER) to activated NFB/STAT3 to promote
immune evasion and endocrine therapy resistance. I will further investigate if dual therapy with ER blockade
and checkpoint inhibitors can reverse endocrine resistance in breast cancers in obese hosts. The F99/K00 will
help my transition from predoctoral to postdoctoral research and, ultimately, into an independent investigator.
