Tumor accessibility, heterogeneity, and microenvironment vary between the two classes of malignancies.
Kerry Grens
Kerry served as The Scientist’s news director until 2021. Before joining The Scientist in 2013, she was a stringer for Reuters Health, the senior health and science reporter at...
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Apr 1, 2019
ABOVE: © LAURIE O'KEEFE
Approved CAR T-cell therapies have led to remarkable regressions in cancers of the blood and bone marrow, so-called liquid cancers. Scientists are now hoping to apply CAR T therapy to treat solid tumors. Both types of cancer present challenges.
Brain tumor
© LAURIE O’KEEFE
Blood cancer
© LAURIE O’KEEFE
| Solid tumors | Liquid cancers | |
| Heterogeneity | Cells of a solid tumor do not all present the same mix of antigens on their surfaces, so a given CAR will likely miss some of the cancer. | Although all cancerous B cells present the CD19 antigen targeted by approved CAR T therapies, normal B cells do as well, which can lead to severe side effects when healthy cells are destroyed. |
| Microenvironment | Solid tumors produce immune-suppressing agents such as the checkpoint molecule PD-L1. | The blood is T cells’ home turf, and engineered CAR T cells readily expand once they are introduced into circulation, although an immune overreaction by the cells can lead to cytokine release syndrome. |
| Delivery | A solid mass of cells thousands of layers thick is difficult for T cells to infiltrate. While some trials deliver the cells systemically, others aim to improve efficacy by administering CAR T cells directly to the site of the tumor. | Approved CAR T therapies are infused into the blood where they can easily access malignant B cells. |
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