Targeted gene delivery by free-tissue transfer in oncoplastic reconstruction

Reconstructive flap surgery in head and neck cancer patients: an interdisciplinary view of the challenges encountered by radiation oncologists in postoperative radiotherapy

Background

Major advances have been made in reconstructive surgery in the last decades to reduce morbidity in head and neck cancer. Flaps are now present in 80% of patients with oral cavity cancer to cover anatomic, functional, and cosmetic needs. However, gaps in interdisciplinary innovation transfer from surgery to postoperative radiotherapy (poRT) remain challenging. We aimed to provide an interdisciplinary view of the challenges encountered by radiation oncologists in planning head and neck postoperative radiotherapy.

Methods

A systematic and critical review was conducted to address areas of optimization in surgery and radiology that may be relevant to poRT.

Results

Despite extensive surgical literature on flap techniques and salvage surgery, 13 retrospective series were identified, where flap outcomes were indirectly compared between surgery alone or poRT. These low-evidence studies suggest that radiotherapy accelerates flap atrophy, fibrosis, and osteoradionecrosis and deteriorates functional outcomes. Preliminary evidence suggests that tumor spread occurs at the flap-tissue junction rather than in the flaps. One prospective 15-patient study showed 31.3% vs. 39.2% flap volume reduction without or with poRT. In an international consensus, experts recognized the needs for optimized flap-sparing poRT against flap-related functional deterioration and bone damage. CT, MRI, and PET-CT modalities show potential for the delineation of the junction area between native tissues and flap for flap segmentation and to characterize flap-specific changes quantitatively and correlate them with patterns of relapse or complications.

Conclusion

Flap management in poRT is insufficiently documented, but poRT seems to damage flaps. Current gaps in knowledge underscore the need for prospective flap assessment and interdisciplinary trials investigating flap morbidity minimization by flap-sparing poRT planning.

Thermosensitive Polymer Conjugated Prodrug-Activating Enzyme with Enhanced Tumor Retention and Antitumor Efficacy

Enzyme-activated prodrug therapy has emerged as an effective strategy for cancer therapy. However, the inefficient delivery of prodrug-activating enzymes into tumor tissues leads to unsatisfactory antitumor efficacy and undesirable toxicity to normal tissues. Herein, we report in situ growth of a thermosensitive polymer of poly(diethylene glycol) methyl ether methacrylate (PDEGMA) from horseradish peroxidase (HRP) to yield a HRP-PDEGMA conjugate with well-retained activity as compared to HRP. The conjugate shows a sharp phase transition behavior with a lower critical solution temperature of 23 °C. The conjugate catalyzes the conversion of non-cytotoxic indole-3-acetic acid (IAA) into cytotoxic species for killing tumor cells. Notably, the PDEGMA conjugation not only increases the stability and cellular uptake of HRP but also prolongs the tumor retention time of HRP upon intratumoral injection. As a result, in mice bearing melanoma, the conjugate inhibits the growth of melanoma much more efficiently than HRP. These results demonstrate that the thermosensitive polymer conjugation of an enzyme is an effective strategy that can enhance the antitumor efficacy of an enzyme-activated prodrug.

Selective Microvascular Tissue Transfection Using Minicircle DNA for Systemic Delivery of Human Coagulation Factor IX in a Rat Model Using a Therapeutic Flap

BACKGROUND

Gene therapy is a promising treatment for protein deficiency disorders such as hemophilia B. However, low tissue selectivity and efficacy are limitations of systemic vector delivery. The authors hypothesized that selective transfection of rat superficial inferior epigastric artery flaps could provide systemic delivery of coagulation factor IX, preventing the need for systemic vector administration.

METHODS

Minicircle DNA containing green fluorescent protein, firefly luciferase, and human coagulation factor IX was created. Vector constructs were validated by transfecting adipose-derived stromal cells isolated from Wistar rat superficial inferior epigastric artery flaps and evaluating transgene expression by fluorescence microscopy, bioluminescence, and enzyme-linked immunosorbent assay. Minicircle DNA luciferase (10 and 30 μg) was injected into murine (wild-type, C57/BL/6) inguinal fat pads (n = 3) and followed by in vivo bioluminescence imaging for 60 days. Wistar rat superficial inferior epigastric artery flaps were transfected with minicircle DNA human coagulation factor IX (n = 9) with plasma and tissue transgene expression measured by enzyme-linked immunosorbent assay at 2 and 4 weeks.

RESULTS

Transfected adipose-derived stromal cells expressed green fluorescent protein for 30 days, luciferase for 43 days, and human coagulation factor IX (21.9 ± 1.2 ng/ml) for 28 days in vitro. In vivo murine studies demonstrated dose-dependence between minicircle DNA delivery and protein expression. Ex vivo rat superficial inferior epigastric artery flap transfection with minicircle DNA human coagulation factor IX showed systemic transgene expression at 2 (266.6 ± 23.4 ng/ml) and 4 weeks (290.1 ± 17.1 ng/ml) compared to control tissue (p < 0.0001).

CONCLUSIONS

Rat superficial inferior epigastric artery flap transfection using minicircle DNA human coagulation factor IX resulted in systemic transgene detection, suggesting that selective flap or angiosome-based tissue transfection may be explored as a treatment for systemic protein deficiency disorders such as hemophilia B.

The future application of nanomedicine and biomimicry in plastic and reconstructive surgery

Plastic surgery encompasses a broad spectrum of reconstructive challenges and prides itself upon developing and adopting new innovations. Practice has transitioned from microsurgery to supermicrosurgery with a possible future role in even smaller surgical frontiers. Exploiting materials on a nanoscale has enabled better visualization and enhancement of biological processes toward better wound healing, tumor identification and viability of tissues, all cornerstones of plastic surgery practice. Recent advances in nanomedicine and biomimicry herald further reconstructive progress facilitating soft and hard tissue, nerve and vascular engineering. These lay the foundation for improved biocompatibility and tissue integration by the optimization of engineered implants or tissues. This review will broadly examine each of these technologies, highlighting areas of progress that reconstructive surgeons may not be familiar with, which could see adoption into our armamentarium in the not-so-distant future.

Lentivirus-mediated CDglyTK gene-modified free flaps by intra-artery perfusion show targeted therapeutic efficacy in rat model of breast cancer

Background

Free flap-mediated gene therapy in the tumor bed following surgical resection is a promising approach in cancer targeted treatment of residual disease. We investigated the selective killing efficacy of a lentivirus-mediated cytosine deaminase-thymidine kinase (CDglyTK) gene in transplanted breast cancer delivered into a free flap by intra-artery perfusion.

Methods

Proliferation, apoptosis, and cell cycle of rat SHZ-88 breast cancer cells transfected with a lentivirus-mediated CD/TK gene were measured following treatment with ganciclovir and 5-flucytosine in vitro. A model of residual disease of breast cancer in a rat superficial inferior epigastric artery (SIEA) flap model was used to study the therapeutic potential of a double suicide CD/TK and prodrug system in vivo.

Results

Killing efficacy of the double suicide CD/TK and prodrug system on SHZ-88 cells was mediated by increased apoptosis and cell cycle arrest at the G1 phase with significant bystander effect. Following recombinant lentivirus transfection of rat SIEA flap by intra-artery perfusion, CD/TK gene expression was limited to the flap, and the volume and weight of transplanted tumors were significantly reduced without observable toxicity.

Conclusions

SIEA flaps transfected with a lentivirus-mediated CDglyTK gene by intra-artery perfusion effectively suppress transplanted breast tumor growth without obvious systemic toxic effects in rats.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-6111-5) contains supplementary material, which is available to authorized users.

Genetically modified lentiviruses that preserve microvascular function protect against late radiation damage in normal tissues

Improvements in cancer survival mean that long-term toxicities, which contribute to the morbidity of cancer survivorship, are being increasingly recognized. Late adverse effects (LAEs) in normal tissues after radiotherapy (RT) are characterized by vascular dysfunction and fibrosis causing volume loss and tissue contracture, for example, in the free flaps used for immediate breast reconstruction after mastectomy. We evaluated the efficacy of lentivirally delivered superoxide dismutase 2 (SOD2) overexpression and connective tissue growth factor (CTGF) knockdown by short hairpin RNA in reducing the severity of LAEs in an animal model of free flap LAEs. Vectors were delivered by intra-arterial injection, ex vivo, to target the vascular compartment. LVSOD2 and LVshCTGF monotherapy before irradiation resulted in preservation of flap volume or reduction in skin contracture, respectively. Flaps transduced with combination therapy experienced improvements in both volume loss and skin contracture. Both therapies reduced the fibrotic burden after irradiation. LAEs were associated with impaired vascular perfusion, loss of endothelial permeability, and stromal hypoxia, which were all reversed in the treatment model. Using a tumor recurrence model, we showed that SOD2 overexpression in normal tissues did not compromise the efficacy of RT against tumor cells but appeared to enhance it. LVSOD2 and LVshCTGF combination therapy by targeted, intravascular delivery reduced LAE severities in normal tissues without compromising the efficacy of RT and warrants translational evaluation as a free flap-targeted gene therapy.

Adenovirally delivered enzyme prodrug therapy with herpes simplex virus-thymidine kinase in composite tissue free flaps shows therapeutic efficacy in rat models of glioma

INTRODUCTION

Free flap gene therapy exploits a novel therapeutic window when viral vectors can be delivered into a flap ex vivo. The authors investigated the therapeutic potential of an adenovirally-delivered thymidine kinase/ganciclovir prodrug system expressed following vector delivery into a free flap.

METHODS

The authors demonstrated direct in vitro cytotoxicity by treating a panel of malignant cell lines with the thymidine kinase/ganciclovir system and demonstrated significant cell kill proportional to the multiplicity of infection of adenoviral vector expressing thymidine kinase. Bystander cytotoxicity was demonstrated using conditioned media from producer cells (expressing adenovirally-delivered thymidine kinase and treated with ganciclovir) to demonstrate cytotoxicity in naive tumor cells. The authors investigated the effect of adenoviral vector expressing thymidine kinase/ganciclovir therapy in vivo, using models of microscopic and macroscopic residual disease in a rodent superficial inferior epigastric artery flap model.

RESULTS

The authors observed retardation of tumor volume growth in both microscopic (p = 0.0004) and macroscopic (p = 0.0005) residual disease models and prolongation of animal survival. Gene expression studies demonstrated that viral genomic material was found predominantly in flap tissues but declined over time.

CONCLUSIONS

The authors describe the utility of virally delivered enzyme/prodrug therapy, using a free flap as a vehicle for delivery. They discuss the merits and limitations of this approach and the unique role of therapeutic free flaps among reconstructive techniques available to the plastic surgeon.

The role of gene therapy in regenerative surgery: updated insights

BACKGROUND

In the past two decades, regenerative surgeons have focused increasing attention on the potential of gene therapy for treatment of local disorders and injuries. Gene transfer techniques may provide an effective local and short-term induction of growth factors without the limits of other topical therapies. In 2002, Tepper and Mehrara accurately reviewed the topic: given the substantial advancement of research on this issue, an updated review is provided.

METHODS

Literature indexed in the National Center for Biotechnology Information database (PubMed) has been reviewed using variable combinations of keywords ("gene therapy," "regenerative medicine," "tissue regeneration," and "gene medicine"). Articles investigating the association between gene therapies and local pathologic conditions have been considered. Attention has been focused on articles published after 2002. Further literature has been obtained by analysis of references listed in reviewed articles.

RESULTS

Gene therapy approaches have been successfully adopted in preclinical models for treatment of a large variety of local diseases affecting almost every type of tissue. Experiences in abnormalities involving skin (e.g., chronic wounds, burn injuries, pathologic scars), bone, cartilage, endothelia, and nerves have been reviewed. In addition, the supporting role of gene therapies to other tissue-engineering approaches has been discussed. Despite initial reports, clinical evidence has been provided only for treatment of diabetic ulcers, rheumatoid arthritis, and osteoarthritis.

CONCLUSIONS

Translation of gene therapy strategies into human clinical trials is still a lengthy, difficult, and expensive process. Even so, cutting-edge gene therapy-based strategies in reconstructive procedures could soon set valuable milestones for development of efficient treatments in a growing number of local diseases and injuries.