Modular nanotransporters: a multipurpose in vivo working platform for targeted drug delivery

Abstract

Background: Modular nanotransporters (MNT) are recombinant multifunctional polypeptides created to exploit a cascade of cellular processes, initiated with membrane receptor recognition to deliver selective short-range and highly cytotoxic therapeutics to the cell nucleus. This research was designed for in vivo concept testing for this drug delivery platform using two modular nanotransporters, one targeted to the α-melanocyte-stimulating hormone (αMSH) receptor overexpressed on melanoma cells and the other to the epidermal growth factor (EGF) receptor overexpressed on several cancers, including glioblastoma, and head-and-neck and breast carcinoma cells. Methods: In vivo targeting of the modular nanotransporter was determined by immunofluorescence confocal laser scanning microscopy and by accumulation of 125 I-labeled modular nanotransporters. The in vivo therapeutic effects of the modular nanotransporters were assessed by photodynamic therapy studies, given that the cytotoxicity of photosensitizers is critically dependent on their delivery to the cell nucleus.Results: Immunohistochemical analyses of tumor and neighboring normal tissues of mice injected with multifunctional nanotransporters demonstrated preferential uptake in tumor tissue, particularly in cell nuclei. With 125 I-labeled MNT{αMSH}, optimal tumor:muscle and tumor:skin ratios of 8:1 and 9.8:1, respectively, were observed 3 hours after injection in B16-F1 melanoma-bearing mice. Treatment with bacteriochlorin p-MNT{αMSH} yielded 89%-98% tumor growth inhibition and a two-fold increase in survival for mice with B16-F1 and Cloudman S91 melanomas. Likewise, treatment of A431 human epidermoid carcinoma-bearing mice with chlorin e 6 -MNT{EGF} resulted in 94% tumor growth inhibition compared with free chlorin e 6 , with 75% of animals surviving at 3 months compared with 0% and 20% for untreated and free chlorin e 6 -treated groups, respectively. Conclusion:The multifunctional nanotransporter approach provides a new in vivo functional platform for drug development that could, in principle, be applicable to any combination of cell surface receptor and agent (photosensitizers, oligonucleotides, radionuclides) requiring nuclear delivery to achieve maximum effectiveness.

Modular Nanotransporters for Targeted Intracellular Delivery of Drugs: Folate Receptors as Potential Targets

“…injection. These results confirmed the ability of MNT to be selectively delivered to tumors bearing the receptor of interest in vivo [26, 28]. Immunohistochemical analyses of tumor and neighboring normal tissues isolated from Cloudman S91 melanoma bearing mice injected i.v.…”

“…Therefore, the problem of creating the optimal PS distribution in the cell becomes critical, especially taking into account that the most sensitive target for PSs is the cell nucleus [13, 22–24], where uptake of free PSs has not been detected [13, 25]. Thus, there exists a real possibility to significantly increase the effectiveness of PSs by achieving their delivery to the nucleus of target cells, reducing doses required to reach a therapeutic threshold, and thus diminishing side effects [8, 26–28]. …”

“…Currently, several kinds of MNTs [8, 16, 29], including the most extensively studied versions with ligands for melanocortin receptor type 1 (MC1R) [12, 24, 26, 28] and epidermal growth factor receptor (EGFR) [22, 23, 25–27, 37, 38] have been created. However, numerous growth factor receptors are known whose expression is highly increased during tumorigenesis.…”

Radiolabeling and in vitro evaluation of 67Ga-NOTA-modular nanotransporter – A potential Auger electron emitting EGFR-targeted radiotherapeutic

“…Having established that MNT-mediated nuclear delivery of short-range therapeutics such as photosensitizers [12,13,16], and α-particle-emitting radionuclides [7] increased their therapeutic effect, we hypothesized that MNT also could be a useful carrier for delivering ultra-short range Auger electron-emitting radionuclides to the cell nucleus. Although previous work demonstrated proof of concept with the prototypical Auger electron-emitting radionuclide 125 I, its 60-day half-life is not ideal for targeted radiotherapy application in patients [21].…”

“…The 76.3-kDa MNT used in the present study contained epidermal growth factor (EGF) as the ligand module to be able to target the multiple malignancies including breast cancer and glioblastoma that overexpress EGF receptors (EGFR) [10,11]. Previous studies established that this MNT was highly effective in enhancing the cytotoxicity of short range of action photosensitizers [12,13] and α-particles [7] against EGFR-expressing cancer cells. Moreover, we have recently demonstrated the potential utility of MNT as a delivery platform for Auger electron emitters in proof of principle studies with 125 I using the residualizing prosthetic agent N -succinimidyl 4-guanidinomethyl-3-[ 125 I]iodobenzoate ([ 125 I]SGMIB) [14].…”