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Elastin-like polypeptides (ELP) are thermally responsive polypeptides that are soluble in solutions at 37°C, but which aggregate above 42°C. ELP can be used as effective carrier systems of anticancer molecules, because they can be targeted to tumor sites through the application of local hyperthermia. Since molecular size largely influences how successfully therapeutic agents can cross the vasculatures of tumors, it was crucial to determine an optimal molecular size. In this study, we designed and evaluated three ELP macromolecules with varying molecular weights (43, 63, and 122 kDa), with the goal of determining which would optimize the ELP drug delivery system. The N-terminus of the ELP macromolecule was modified with the cell penetrating peptide Bac to enhance intratumoral and intracellular uptake, and it was also confirmed that each polypeptide had the target transition temperature of 37-42°C and the results of the studies, using tumor-bearing mice, showed that the tumor accumulations increased in the case of all three peptides when local hyperthermia was applied, but that the elimination patterns from these tumors varied according to peptide size. Local hyperthermia was found to produce prolonged retention of all ELP conjugates in tumors except Bac-ELP43. In addition, the pharmacokinetic analysis showed that two larger polypeptides with 63 and 122 kDa have increased AUC in comparison with the 43 kDa polypeptide. These results suggest that, when combined with local hyperthermia, the larger ELP conjugates (63 and 122 kDa) have advantages over the smaller Bac-ELP43 polypeptide in terms of enhanced permeability and higher retention effects., (Copyright © 2014 Elsevier B.V. All rights reserved.)

S100B, a glial-secreted protein, is believed to play a major role in neurodegeneration in Alzheimer's disease, Down syndrome, traumatic brain injury, and spinocerebellar ataxia type 1 (SCA1). SCA1 is a trinucleotide repeat disorder in which the expanded polyglutamine mutation in the protein ataxin-1 primarily targets Purkinje cells of the cerebellum. Currently, the exact mechanism of S100B-mediated Purkinje cell damage in SCA1 is not clear. However, here we show that S100B may act via the activation of the receptor for advanced glycation end product (RAGE) signaling pathway, resulting in oxidative stress-mediated injury to mutant ataxin-1-expressing neurons. To combat S100B-mediated neurodegeneration, we have designed a selective thermally responsive S100B inhibitory peptide, Synb1-ELP-TRTK. Our therapeutic polypeptide was developed using three key elements: (1) the elastin-like polypeptide (ELP), a thermally responsive polypeptide, (2) the TRTK12 peptide, a known S100B inhibitory peptide, and (3) a cell-penetrating peptide, Synb1, to enhance intracellular delivery. Binding studies revealed that our peptide, Synb1-ELP-TRTK, interacts with its molecular target S100B and maintains a high S100B binding affinity as comparable with the TRTK12 peptide alone. In addition, in vitro studies revealed that Synb1-ELP-TRTK treatment reduces S100B uptake in SHSY5Y cells. Furthermore, the Synb1-ELP-TRTK peptide decreased S100B-induced oxidative damage to mutant ataxin-1-expressing neurons. To test the delivery capabilities of ELP-based therapeutic peptides to the cerebellum, we treated mice with fluorescently labeled Synb1-ELP and observed that thermal targeting enhanced peptide delivery to the cerebellum. Here, we have laid the framework for thermal-based therapeutic targeting to regions of the brain, particularly the cerebellum. Overall, our data suggest that thermal targeting of ELP-based therapeutic peptides to the cerebellum is a novel treatment strategy for cerebellar neurodegenerative disorders., (Copyright © 2011 IBRO. Published by Elsevier Ltd. All rights reserved.)

The chemotherapeutic drug doxorubicin (Dox) is widely used as an antitumor agent in hematological malignancies and solid tumors. However, one of the limitations of its clinical use is that systemic administration of an effective dose of Dox results in nonselective cardiac toxicity and myelosuppression. In order to minimize this nonspecific toxicity, Elastin-like polypeptide (ELP) was examined for its ability to serve as a macromolecular carrier for thermally targeted delivery of Dox. The ELP-based doxorubicin delivery vehicle (Tat-ELP-GFLG-Dox) consists of: (1) a peptide derived from the HIV-1 Tat protein to facilitate its cellular uptake, (2) ELP to allow thermal targeting, and (3) the lysosomally degradable glycylphenylalanylleucylglycine (GFLG) spacer and a cysteine residue conjugated to a thiol reactive doxorubicin derivative. Cytotoxicity of Tat-ELP-GFLG-Dox in MES-SA uterine sarcoma cells was enhanced 20-fold when aggregation of ELP was induced with hyperthermia. The ELP delivered doxorubicin displayed a cytoplasmic distribution and induced temperature dependent caspase activation.

Topoisomerase II inhibitors are widely used in cancer chemotherapy. However, their use is limited by severe adverse effects to normal tissues, including cardiotoxicity. One approach to reduce the cytotoxicity in normal tissues may be to sensitize cancer cells to the toxicity of these agents, allowing them to be administered in a lower and safer dose. A hallmark of many types of cancer is overexpression of c-Myc, and a molecule which targets c-Myc will affect the cancer cells more significantly than the normal tissues. This report demonstrates that pretreatment of cells with a polypeptide, which inhibits c-Myc transcriptional function causes cells to be more susceptible to the topoisomerase II inhibitors doxorubicin and etoposide. Inhibition of c-Myc and Max dimerization by this polypeptide leads to as much as a 2-fold reduction in the doxorubicin and etoposide IC(50) in three different cell lines tested. Furthermore, the c-Myc inhibitor affects the cell cycle distribution of MCF-7 breast cancer cells by enhancing the G(0)/G(1) accumulation induced by doxorubicin and etoposide. We have shown that this effect is not due to enhanced drug accumulation or inhibited drug efflux. Rather, it is likely due to the transcriptional consequences of c-Myc inhibition, specifically reduction in the levels of the polyamine synthesizing enzyme ornithine decarboxylase. In summary, our results suggest that polypeptides, which inhibit c-Myc transcriptional function, may prove to be a useful tool in combination therapy with topoisomerase II inhibiting drugs.