In vivo antitumor effects of electrochemotherapy in a tongue cancer model

Chronic mechanical trauma/irritation and oral carcinoma: A systematic review showing low evidence to support an association

BACKGROUND

Chronic trauma of oral mucosa, resulting from repeated and persistent mechanical irritative action of an intraoral injury agent, has repeatedly been reported to be possibly implicated in the development of oral squamous cell carcinoma (OSCC).

OBJECTIVES

The present systematic review aimed to assess whether chronic mechanical trauma can be considered a risk factor for OSCC.

DATA SOURCES

PubMed, CENTRAL (Cochrane Central Register of Controlled Trials), Scopus; EMBASE, Web of Science.

STUDY ELIGIBILITY CRITERIA

Cohort studies comparing OSCC incidence among subjects with/without chronic mechanical trauma or case-control or cross-sectional studies comparing chronic mechanical trauma among subjects with/without OSCC.

RESULTS

Only one prospective case-control study fulfilled the inclusion criteria, but the quality of the evidence provided is not enough to define trauma as a risk factor for OSCC. The main limitation is the presence of only one case-control study at high risk of bias. In the absence of strong evidence supporting the role of trauma in OSCC, a thorough discussion on trauma and carcinogenesis has been performed.

CONCLUSIONS

Available evidence does not support an active role for chronic trauma in oral carcinogenesis, neither as promoter nor as progressor factor. Prospective cohort studies able to better assess trauma in OSCC are needed.

Animal models for the study of squamous cell carcinoma of the upper aerodigestive tract: a historical perspective with review of their utility and limitations. Part A. Chemically-induced de novo cancer, syngeneic animal models of HNSCC, animal models of transplanted xenogeneic human tumors

Understanding the complex histological, genetic and molecular changes that lead to malignant transformation of squamous epithelia of the head and neck will likely guide the development of methods for improved diagnosis, monitoring and treatment of head and neck squamous cell carcinoma (HNSCC). The development and use of animal models that closely mimic the histopathology and molecular pathogenesis of HNSCC in humans would greatly expand the research possibilities and provide a means of testing potential therapeutic agents. However, many available animal models of HNSCC fall short of this objective. In order for investigators to select the appropriate model to answer scientific questions, it is important to understand the benefits and limitations of available animal models for the study of HNSCC. The purpose of this work is to give an overview of the most pertinent animal models of HNSCC, and to discuss future directions of research in this field.

The role of intratumour therapy with electroporation and bleomycin in the management of advanced squamous cell carcinoma of the head and neck

OBJECTIVES

To determine the safety and efficacy of electroporation with bleomycin in patients with advanced squamous cell carcinoma of the head and neck.

METHODS

Two open-label, multicenter, single-arm Phase II studies of intratumour electroporation therapy. Sixty-two patients with 86 squamous cell carcinoma tumours of the head and neck were enrolled. Twenty-five patients were treated with bleomycin alone. Fifty-four patients (17 initially treated with bleomycin alone) were treated with electroporation and bleomycin therapy. Local tumour response was measured.

RESULTS

In the bleomycin alone group, one tumour showed a partial response and 36 tumours showed no response to treatment. In the bleomycin with electroporation groups, 17 tumours showed complete response, 22 tumours showed partial response and 30 failed to achieve more than a 50% reduction in tumour size (no response). Bleomycin with electroporation had a significantly (p<0.001) greater number of patients showing a partial or complete response to the therapy when compared to bleomycin alone. Thirteen adverse events were reported which included five episodes of local bleeding, six local infections, one local tongue swelling and one cardiac arrhythmia.

CONCLUSIONS

Fifty-seven percent of squamous cell carcinomas of the head and neck demonstrated a partial or complete response to intratumour electroporation with bleomycin suggesting that further work investigating its use as a treatment for local control of these lesions should be pursued.

Enhancing the effectiveness of drug-based cancer therapy by electroporation (electropermeabilization)

Many conventional chemotherapeutic drugs, as well as DNA for cancer gene therapy, require efficient access to the cell interior to be effective. The cell membrane is a formidable barrier to many of these drugs, including therapeutic DNA constructs. Electropermeabilization (EP, often used synonymously with "electroporation") has become a useful method to temporarily increase the permeability of the cell membrane, allowing a broad variety of molecules efficient access to the cell interior. EP is achieved by the application of short electrical pulses of relatively high local field strength to the target tissue of choice. In cancer therapy, EP can be applied in vivo directly to the tumor to be treated, in order to enhance intracellular uptake of drugs or DNA. Alternatively, EP can be used to deliver DNA into cells of healthy tissue to achieve longer-lasting expression of cancer-suppressing genes. In addition, EP has been used in ex vivo therapeutic approaches for the transfection of a variety of cells in suspension. In this paper, we communicate results related to the development of a treatment for squamous cell carcinomas of the head and neck, using electropermeabilization to deliver the drug bleomycin in vivo directly into the tumor cells. This drug, which is not particularly effective as a conventional therapeutic, becomes highly potent when the intracellular concentration is enhanced by EP treatment. In animal model experiments we found a drug dose of 1 U/cm(3) tumor tissue (delivered in 0.25 mL of an aqueous solution/cm3 tumor tissue) and an electrical field strength of 750 V/cm or higher to be optimal for the treatment of human squamous cell tumors grown subcutaneously in mice. Within 24-48 hours, the majority of tumor cells are rapidly destroyed by this bleomycin-electroporation therapy (B-EPT). This raises the concern that healthy tissue may be similarly affected. In studies with large animals we showed that normal muscle and skin tissue, normal tissue surrounding major blood vessels and nerves, as well as healthy blood vessels and nerves themselves, are much less affected than tumor tissue. Normal tissues did show acute, focal, and transitory effects after treatment, but these effects are relatively minor under standard treatment conditions. The severity of these effects increases with the number of electric pulse cycles and applied voltage. The observed histological changes resolved 20 to 40 days after treatment or sooner, even after excessive EP treatment. Thus, B-EPT is distinct from other ablative therapies, such as thermal, cryo, or photodynamic ablation, which equally affect healthy and tumor tissue. In comparison to surgical or radiation therapy, B-EPT also has potential as a tissue-sparing and function-preserving therapy. In clinical studies with over 50 late stage head and neck cancer patients, objective tumor response rates of 55-58%, and complete tumor response rates of 19-30% have been achieved.

Theory and in vivo application of electroporative gene delivery

Efficient and safe methods for delivering exogenous genetic material into tissues must be developed before the clinical potential of gene therapy will be realized. Recently, in vivo electroporation has emerged as a leading technology for developing nonviral gene therapies and nucleic acid vaccines (NAV). Electroporation (EP) involves the application of pulsed electric fields to cells to enhance cell permeability, resulting in exogenous polynucleotide transit across the cytoplasmic membrane. Similar pulsed electrical field treatments are employed in a wide range of biotechnological processes including in vitro EP, hybridoma production, development of transgenic animals, and clinical electrochemotherapy. Electroporative gene delivery studies benefit from well-developed literature that may be used to guide experimental design and interpretation. Both theory and experimental analysis predict that the critical parameters governing EP efficacy include cell size and field strength, duration, frequency, and total number of applied pulses. These parameters must be optimized for each tissue in order to maximize gene delivery while minimizing irreversible cell damage. By providing an overview of the theory and practice of electroporative gene transfer, this review intends to aid researchers that wish to employ the method for preclinical and translational gene therapy, NAV, and functional genomic research.