Clostridium perfringens Enterotoxin as a Novel-Targeted Therapeutic for Brain Metastasis

Abstract

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 f8 months, and treatment often leads to neurologic dysfunction in longterm 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. [Cancer Res 2007;67(17):7977-82]

Novel Clostridium perfringens enterotoxin suicide gene therapy for selective treatment of claudin-3- and -4-overexpressing tumors

“…Other in vivo studies of external therapeutic application of recombinant CPE also reported strong necrosis in the tumor tissues. 33,[35][36][37] In conclusion, we report the successful tumor-targeted CPE gene therapy in vitro and in vivo. This approach efficiently eradicates tumor cells, and provides an attractive therapeutic option for the potential local treatment of refractory solid tumors (including unresectable tumor lesions, residual tumors or recurrences), originating from colon, mammary, pancreas or prostate cancer, which overexpress claudin-3 or -4.…”

“…Application of recombinant CPE protein leads to the dose-dependent rapid eradication of claudin-4-or claudin-3-overexpressing pancreas, breast or colon cancer cells in vitro and in vivo. 17,18,[33][34][35][36][37] The intratumoral in vivo application of recombinant CPE did not induce toxinassociated side effects, supporting its great therapeutic potential. However, these approaches require repeated, almost continuous regional or loco-regional application of recombinant CPE at doses ranging from 0.5 to 1.0 mg CPE per application to achieve therapeutic effects.…”

“…However, these approaches require repeated, almost continuous regional or loco-regional application of recombinant CPE at doses ranging from 0.5 to 1.0 mg CPE per application to achieve therapeutic effects. 33,36,37 Furthermore, high interstitial pressure in the tumor might hinder proper distribution of externally applied CPE limiting its therapeutic action. 38 Alternatively, intratumoral gene transfer of CPE-expressing vectors could significantly improve duration of toxin availability associated with optimized intratumoral distribution and accumulation.…”

A Key Claudin Extracellular Loop Domain is Critical for Epithelial Barrier Integrity

“…18 -21 This further underscores a role for claudin EL domains in the formation and maintenance of TJ barriers and suggests a pharmacological approach to transiently increase paracellular permeability. [22][23][24] Although the specificity of CPE can be an advantage for this approach, 20,25 whether CPE interacts with other claudins is still being explored. The recent structural analysis of the CPE claudin binding site is an important step in determining the range of claudins other than claudin-3 and claudin-4 with the ability to interact with CPE.…”

Recent Advances in Claudin-Targeting Technology

“…14,15) Furthermore, administration of Clostridium perfringens enterotoxin (cPE), whose receptor is cL-3 and cL-4, showed antitumor activity. [16][17][18] Because cL-4 is highly expressed in the epithelium covering mucosal immune tissues, the delivery of antigen to these tissues using a cL-4 ligand may lead to the development of mucosal vaccines. 19) Therefore cLs are very attractive as targets for drug delivery.…”