Studies examining quantitative in vivo imaging of breast cancer-targeted,therapeutic human mast cells

ABSTRACT
Breast cancer (BC) continues to be a serious health problem in the United States. The oncogene HER2/neu
and the folate receptor alpha (FRa) are overexpressed in BC and validated targets for cancer therapeutics.
The humanized IgG1 monoclonal antibody (Ab) trastuzumab (Herceptin®) has been approved by the FDA for
the treatment of advanced BC and several humanized IgG Abs to FRa are in clinical trials. However, their
efficacy is limited and additional strategies to target HER2/neu and FRa overexpressing tumors are still
urgently needed. Interestingly, high densities of mast cells (MC) in BC tumors are associated with favorable
prognoses. We discovered that human adipose cells can be differentiated into autologous, fully functional MC
capable of releasing anti-tumor mediators TNF-a and GM-CSF upon FceRI stimulation and inducing BC cell
death. In addition, we have shown for the first time that primary human MC and their stem cell precursors can
be transduced with a lentiviral vector carrying green fluorescence (GFP) protein opening up the possibility they
could be transduced with other tumor killing molecules (e.g. TRAIL, granzyme, etc.) to create new ways to treat
BC by directing immune evading cells with anti-tumor agents to tumors. However, it is important to determine if
the ADMC will target cancer cells in vivo, determine the initial pharmacokinetics of this interaction, and
establish proof-of-principle in regards to efficacy. Our overall hypothesis is ADMC can be transduced with
genetic imaging modules that will allow for the visualization and quantification of binding to luciferase
transduced BC cells/tumors in vivo after i.v. injection. Herein, we will use a novel and safer lentivirus
vector system to transduce ADMC with genetic modules that will allow for in vivo visualization without affecting
BC cell killing capabilities by comparing their ability to induce BC cell death compared to non-transduced
ADMC. Further, we will visualize and quantify ADMC binding to BC cells in vivo and assess overt signs of
toxicology activity in xenograft tumor models.