Following are public and technical abstracts for the Targeting B7-H3 Using CAR T-Cells project funded by the Department of Defense Kidney Cancer Research Program (KCRP) for 2017.
Principal Investigator: Hongwei Du
Institution: University of North Carolina at Chapel Hill
Funding Mechanism: Concept Award
Award Amount: $116,625
Public Abstract
Early stage kidney cancer is curable by partial or radical nephrectomy. However, the 5-year survival rate of patients with distant metastasis is less than 20%, without much improvement over the past decade. The adoptive transfer of chimeric antigen receptor (CAR) T cells (CAR-Ts) is emerging as a potential curative approach for cancer patients. Here, I propose that B7-H3 is an ideal candidate for CAR-T-based therapy in renal cell carcinoma (RCC) because it is aberrantly expressed in nearly 20% of tumor cells and 95% of tumor vasculature in clear cell RCC.
In my proposal, I will investigate whether CAR-Ts targeting the B7-H3 antigen (B7-H3.CAR-Ts) are effective in RCC and investigate whether B7-H3.CAR-Ts can also target the tumor-associated vasculature. The B7-H3.CAR-Ts I generated are very effective in preclinical models of other B7-H3+ solid tumors such as pancreatic cancer. Thus, I am confident that B7-H3.CAR-Ts can also effectively target B7- H3+ RCC.
The project is highly translational, and its long-term goal is to pave the way for developing a clinical trial to treat patients with metastatic RCC using B7-H3.CAR-Ts. If successful, B7-H3.CAR-Ts may represent a curable opportunity for metastatic kidney cancer patients and could also translate to other cancers with B7-H3 expression.
Technical Abstract
Background: Adoptive transfer of chimeric antigen receptor (CAR) T-cells (CAR-Ts) targeting CD19 received FDA approval for the treatment of relapsed B-cell malignancies. However, the development of CAR-Ts in solid tumors, including kidney cancer, remains challenging because tumor-associated antigens that are targetable by CAR-Ts are limited, generally not exclusively expressed by cancer cells, and act as passengers but not as drivers of tumorigenesis, causing antigenic drift. CAR-Ts targeting carboxyanhydrase-IX (CAIX) have been investigated in renal cell carcinoma (RCC). Unfortunately, due to the severe “on-target off-tumor toxicity,” this approach was not further developed. Thus, novel targets characterized by high expression in tumor cells, but with restricted expression in normal tissues, are urgently needed.
Hypothesis: Here, I propose that B7-H3 is an ideal candidate for CAR-T-based therapy in RCC because it is not expressed in normal organs, such as brain, spinal cord, peripheral nerves, muscle, heart, lung, and kidney, but it is aberrantly expressed in nearly 20% of tumor cells and 95% of tumor vasculature in clear cell RCC. Furthermore, B7-H3 expression in the tumor vasculature was associated with poor prognosis, indicating that B7-H3 promotes RCC tumor progression. This aspect is highly relevant for cancer immunotherapy, because targeting a molecule that is crucial for tumor progression prevents tumor immune escape due to the down-regulation or loss of the molecule.
Specific Aims: (1) To investigate the antitumor activity of B7-H3.CAR-Ts against B7-H3+ RCC in vitro and in vivo. (2) To investigate whether targeting murine B7-H3+ tumor-associated vasculature with B7-H3.CAR-Ts controls tumor growth.
Study Design
Aim 1: To investigate the antitumor activity of B7-H3.CAR-T against B7-H3+ RCC in vitro and in vivo. To evaluate the antitumor activity of B7-H3.CAR-Ts, control and B7-H3.CAR-Ts will be co-cultured in vitro with B7-H3+ and B7-H3- RCC cell lines. The co-culture supernatant will be collected to measure IFN-gamma and IL2 released by T cells by ELISA, and all cells will be collected at day 5 and analyzed by FACS to measure tumor elimination. I will then establish metastatic RCC models in NSG mice to assess the antitumor activity of B7-H3.CAR-Ts in vivo. Briefly, 1×10^6 tumor cells transduced with Firefly Luciferase (FFluc) will be injected intravenously (i.v.), and 2 weeks later, control and B7-H3.CAR-Ts will be infused also i.v. (5×10^6/mouse). Tumor growth will be monitored weekly by IVIS imaging for 3 months.
Aim 2: To investigate whether targeting murine B7-H3+ tumor-associated vasculature with B7-H3.CAR- Ts controls tumor growth. I will establish an orthotopic RCC tumor model in immunocompetent mice by inoculating the mB7-H3- murine RCC cell lines Renca into the right kidney of BALB/c male mice. Three weeks later, mice will be irradiated with a low-dose irradiation (400 Rad) to create lymphodepletion, and infused i.v. 2 days later with control or B7-H3.CAR-Ts (1×10^7 cells/mouse). Four weeks later, mice will be euthanized and I will assess the tumor size and weight, and evaluate tumor vasculature by IHC staining of the vasculature marker CD31.
Innovation: CAR-T therapy is emerging as a potential curative approach for cancer patients. I have generated novel CAR-Ts that specifically target the B7-H3 antigen (B7-H3.CAR-Ts) and showed effective antitumor activity when targeting pancreatic cancer. The first innovation of this proposal is to test if B7-H3.CAR-Ts control the growth of renal cell carcinoma (RCC) in vitro and in vivo. The second innovation of this proposal is to assess if B7-H3.CAR-Ts can reduce neoangiogenesis in RCC using an immunocompetent syngeneic mouse model, since more than 95% of RCC tumors have aberrant B7-H3 expression in the tumor-associated vasculature.
Impact: The B7-H3.CAR-Ts I generated are very effective in preclinical models of other B7-H3+ solid tumors such as pancreatic cancer. Thus, I am confident that B7-H3.CAR-Ts can also effectively target B7-H3+ RCC. The project is highly translational, and its long-term goal is to pave the way for developing a clinical trial to treat patients with metastatic RCC with B7-H3.CAR-Ts. If successful, B7-H3.CAR-Ts may represent a curable opportunity for metastatic RCC as observed with CD19-specific CAR-Ts in lymphoid malignancies.