Brain
metastasis is the most commonly occurring intracranial
tumor whose incidence seems to be increasing. With standard
therapy, the average survival time of patients is approximately 8 months, and treatment often leads to
neurologic dysfunction in long-term survivors, emphasizing the need for novel
therapeutics.
Clostridium perfringens enterotoxin (CPE) has recently been shown to rapidly and specifically destroy
cancer cells expressing CPE receptors
claudin-3 and
claudin-4. Unfortunately, the utility of CPE is precluded by systemic toxicity because its receptors are expressed in numerous organs. Here, we provide the first preclinical evidence that CPE may be uniquely suited to the local treatment of brain
metastasis. By immunohistochemical analysis,
claudin-3 and
claudin-4 were expressed frequently in
metastases from breast (15 of 18), lung (15 of 20), and colon (12 of 14)
carcinoma, and infrequently in
metastases from
renal cell carcinoma (2 of 16) and
melanoma (2 of 16). In contrast, expression of
claudin-3 and
claudin-4 was absent in adjacent normal brain tissue. Further examination of the central nervous system (CNS) revealed low or undetectable levels of
claudin-3 and
claudin-4 in all regions tested by Western and immunohistochemical analysis. Treatment of
breast cancer cell lines (MCF-7, MDA-MB-468, NT2.5-luc) and normal human astrocytes with CPE in vitro resulted in rapid and dose-dependent cytolysis exclusively in
breast cancer cells, correlating with
claudin-3 and
claudin-4 expression. Moreover, intracranial CPE treatment significantly inhibited
tumor growth and increased survival in two murine models of
breast cancer brain
metastasis, without any apparent local or systemic toxicity. These data suggest that CPE
therapy may have efficacy against a wide variety of
brain metastases without CNS toxicity.