Identification of a tumor-targeting-peptide and development of a tumor-targeted-cytokine vector for systemic treatment of primary and metastatic malignancies

Advances in cancer therapies continue to be improved, yet cancer continues to be one of the deadliest diseases in the world. Harnessing the power of the body’s immune system to attack cancer is a promising strategy that can further improve therapies for neoplastic diseases. As part of this strategy, cytokines such as interleukin (IL) 2 and interferon á are currently accepted cancer treatments, and other cytokines such as IL12 and GM-CSF also show potential as new treatments. Clinical trials with these cytokines have shown less than acceptable therapeutic efficacy and toxicities, but tumor-targeting motifs can improve these effects. Both antibodies and peptides specific for tumor antigens have been used in recombinant protein and gene therapy systems to increase the intratumoral cytokine accumulation and decrease systemic toxicities. Still, these treatments have not been capable of overcoming the obstacles for clinical acceptance. The hypothesis tested in this dissertation is that inserting tumor-targeting peptide coding sequences into IL12 plasmid DNA will create a novel systemic gene therapy approach which will increase the antitumor efficacy and decrease toxicity for cancer treatments. To accomplish this goal, a reporter gene mediated screening strategy was developed to identify a peptide which can target multiple tumor models. While preparing this method, it was discovered that these peptides can have a strong effect on the activity of the conjugated reporter gene. Once this strategy was finalized, the peptide VNTANST was found to increase the intratumoral accumulation of the reporter gene in five tumor models including a human xenogeneic model. The VNTANST coding sequence was then inserted into an IL12 plasmid to examine the antitumor efficacy. In breast adenocarcinoma, squamous cell carcinoma, and colon carcinoma models, VNTANST-IL12 plasmid DNA treatments distal from the tumor site increased tumor inhibition and, in two models, prolonged survival. Also, these treatments reduced the development of metastatic lung tumors in a spontaneous metastatic model. As expected, these tumor-targeted IL12 treatments decreased the level of liver toxicity compared to wild-type treatments. The receptor for VNTANST was identified as vimentin, which is a potentially powerful target for human cancers

Administering plasmid DNA encoding tumor vessel-anchored IFN-α for localizing gene product within or into tumors

Tumor-targeted gene delivery has been intensively studied in the field of gene therapy, but no attention has been given to targeting the therapeutic gene products, which are transcribed and translated from the injected genes, into tumors. Targeting immune stimulatory gene products into tumors is the key to triggering tumor-specific CD8+ T-cell responses and reducing systemic toxicity. To target the gene products generated from the injected genes into tumors, genes encoding the tumor-targeted fusion gene product were generated and administered locally and systemically via electroporation. As anticipated, administration of a therapeutic gene encoding IFN-α and the tumor vessel-targeted peptide CDGRC fusion gene product minimizes the leakage of immunostimulatory cytokine from tumors into the blood circulation, increases the infiltration of CD8+ T cells into tumors, induces a high magnitude of cytotoxic T-cell lysis (CTL) activity, and reduces tumor vessel density. As a result, tumor growth was more significantly inhibited by administering the IFN-α-CDGRC gene than by administering the wild-type IFN-α gene. The same result was obtained with the systemic administration of the tumor-targeted IFN-α gene. This gene product-based tumor-targeted gene therapy approach could complement any other tumor-targeted gene delivery method for improving tumor-targeting efficiency

WSX1 Expression in Tumors Induces Immune Tolerance via Suppression of Effector Immune Cells

Crosstalk between tumor cells and the cognate microenvironment plays a crucial role in tumor initiation and progression. However, only a few genes are known to affect such a crosstalk. This study reveals that WSX1 plays such a role when highly expressed in tumor cells. The expression of WSX1 in Lewis Lung Carcinoma (LLC) and the melanoma cell line AGS induces the death of T cells and inhibits the production of the effector cytokine IFNγ from NK and T cells, resulting in the promotion of tumor growth. These pro-tumorigenic properties of WSX1 are independent of IL27. This key observation reveals a new pathway of tumor-host interaction, which will ultimately lead to better strategies in immune therapy to reverse tumor tolerance

Electroporation Protocols: Preclinical and Clinical Gene Medicine

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Intricacies for Posttranslational Tumor-Targeted Cytokine Gene Therapy

The safest and most effective cytokine therapies require the favorable accumulation of the cytokine in the tumor environment. While direct treatment into the neoplasm is ideal, systemic tumor-targeted therapies will be more feasible. Electroporation-mediated transfection of cytokine plasmid DNA including a tumor-targeting peptide-encoding sequence is one method for obtaining a tumor-targeted cytokine produced by the tumor-bearing patient’s tissues. Here, the impact on efficacy of the location of targeting peptide, choice of targeting peptide, tumor histotype, and cytokine utilization are studied in multiple syngeneic murine tumor models. Within the same tumor model, the location of the targeting peptide could either improve or reduce the antitumor effect of interleukin (IL)12 gene treatments, yet in other tumor models the tumor-targeted IL12 plasmid DNAs were equally effective regardless of the peptide location. Similarly, the same targeting peptide that enhances IL12 therapies in one model fails to improve the effect of either IL15 or PF4 for inhibiting tumor growth in the same model. These interesting and sometimes contrasting results highlight both the efficacy and personalization of tumor-targeted cytokine gene therapies while exposing important aspects of these same therapies which must be considered before progressing into approved treatment options