Preclinical Modeling and Therapeutic Avenues for Cancer Metastasis to the Central Nervous System

De novo GTP synthesis is a metabolic vulnerability for the interception of brain metastases

Patients with brain metastases (BM) face a 90% mortality rate within one year of diagnosis and the current standard of care is palliative. Targeting BM-initiating cells (BMICs) is a feasible strategy to treat BM, but druggable targets are limited. Here, we apply Connectivity Map analysis to lung-, breast-, and melanoma-pre-metastatic BMIC gene expression signatures and identify inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in the de novo GTP synthesis pathway, as a target for BM. We show that pharmacological and genetic perturbation of IMPDH attenuates BMIC proliferation in vitro and the formation of BM in vivo. Metabolomic analyses and CRISPR knockout studies confirm that de novo GTP synthesis is a potent metabolic vulnerability in BM. Overall, our work employs a phenotype-guided therapeutic strategy to uncover IMPDH as a relevant target for attenuating BM outgrowth, which may provide an alternative treatment strategy for patients who are otherwise limited to palliation.

Intratumoral Delivery of Chimeric Antigen Receptor T Cells Targeting CD133 Effectively Treats Brain Metastases

PURPOSE

Brain metastases (BM) are mainly treated palliatively with an expected survival of less than 12 months after diagnosis. In many solid tumors, the human neural stem cell marker glycoprotein CD133 is a marker of a tumor-initiating cell population that contributes to therapy resistance, relapse, and metastasis.

EXPERIMENTAL DESIGN

Here, we use a variant of our previously described CD133 binder to generate second-generation CD133-specific chimeric antigen receptor T cells (CAR-T) to demonstrate its specificity and efficacy against multiple patient-derived BM cell lines with variable CD133 antigen expression.

RESULTS

Using both lung- and colon-BM patient-derived xenograft models, we show that a CD133-targeting CAR-T cell therapy can evoke significant tumor reduction and survival advantage after a single dose, with complete remission observed in the colon-BM model.

CONCLUSIONS

In summary, these data suggest that CD133 plays a critical role in fueling the growth of BM, and immunotherapeutic targeting of this cell population is a feasible strategy to control the outgrowth of BM tumors that are otherwise limited to palliative care. See related commentary by Sloan et al., p. 477.

Therapy of breast cancer brain metastases: challenges, emerging treatments and perspectives

Brain metastases are the most common central nervous system tumors in adults, and incidence of brain metastases is increasing due to both improved diagnostic techniques (e.g. magnetic resonance imaging) and increased cancer patient survival through advanced systemic treatments. Outcomes of patients remain disappointing and treatment options are limited, usually involving multimodality approaches. Brain metastases represent an unmet medical need in solid tumor care, especially in breast cancer, where brain metastases are frequent and result in impaired quality of life and death. Challenges in the management of brain metastases have been highlighted in this review. Innovative research and treatment strategies, including prevention approaches and emerging systemic treatment options for brain metastases of breast cancer, are further discussed.