tirapazamine and Skin-Neoplasms

Although melanoma accounts for only 5.3% of skin cancer, it results in >75% of skin-cancer-related deaths. To avoid disfiguring surgeries on the head and neck associated with surgical excision, there is a clear unmet need for other strategies to selectively remove cutaneous melanoma lesions. Mohs surgery is the current treatment for cutaneous melanoma lesions and squamous and basal cell carcinoma. While Mohs surgery is an effective way to remove melanomas in situ, normal tissue is also excised to achieve histologically negative margins. This paper describes a novel combination therapy of nonthermal plasma (NTP) which emits a multitude of reactive oxygen species (ROS) and the injection of a pharmaceutical agent. We have shown that the effects of NTP are augmented by the DNA-damaging prodrug, tirapazamine (TPZ), which becomes a free radical only in conditions of hypoxemia, which is often enhanced in the tumor microenvironment. In this study, we demonstrate the efficacy of the combination therapy through experiments with B16-F10 and 1205 Lu metastatic melanoma cells both in vitro and in vivo. We also show the safety parameters of the therapy with no significant effects of the therapy when applied to porcine skin. We show the need for the intratumor delivery of TPZ in combination with the surface treatment of NTP and present a model of a medical device to deliver this combination therapy. The importance of functional gap junctions is indicated as a mechanism to promote the therapeutic effect. Collectively, the data support a novel therapeutic combination to treat melanoma and the development of a medical device to deliver the treatment in situ.

Topics: Animals; Combined Modality Therapy; Melanoma; Melanoma, Cutaneous Malignant; Skin Neoplasms; Swine; Tirapazamine; Tumor Microenvironment

The purpose of this investigation was to compare the effect on intratumour quiescent (Q) cells in vivo of hexamethylenetetramine (HMTA) or tirapazamine (TPZ) in combination with gamma-irradiation and cisplatin treatment. Squamous cell carcinoma (SCC) VII tumour-bearing mice were administered 5-bromo-2'-deoxyuridine (BrdU) continuously to label all intratumour proliferating (P) cells. The mice then received HMTA or TPZ intraperitoneally or continuously with or without gamma-irradiation or cisplatin treatment. Other tumour-bearing mice received HMTA or TPZ intraperitoneally immediately after gamma-irradiation. Immediately after gamma-irradiation or cisplatin treatment following HMTA or TPZ, or 24 h after gamma-irradiation followed by HMTA or TPZ, the response of Q cells was assessed in terms of the micronucleus frequency using immunofluorescence staining for BrdU. The response of all tumour cells (P + Q) was determined from the BrdU-non-treated tumours. HMTA was more toxic to the subset of Q cells than to the population of tumour cells as a whole, similar to the findings for TPZ. The radiosensitising effect of HMTA was similar to that of TPZ in both all cells and Q cells. The recovery-inhibiting effect of HMTA was reliable, but not as great as that of TPZ. The cisplatin sensitivity-enhancing effect of HMTA was similar to or slightly greater than that of TPZ. Continuous administration of both HMTA and TPZ resulted in higher radiosensitivity- and cisplatin sensitivity-enhancing effects than did a single i.p. administration. We concluded that, in terms of the total tumour cell killing effect, including killing of Q cells, gamma-irradiation and cisplatin treatment combined with continuous HMTA administration is a promising strategy given that HMTA is used in clinics.

Topics: Animals; Antineoplastic Agents; Carcinoma, Squamous Cell; Cell Hypoxia; Cisplatin; Combined Modality Therapy; Female; Gamma Rays; Infusions, Subcutaneous; Methenamine; Mice; Mice, Inbred C3H; Radiation-Sensitizing Agents; Skin Neoplasms; Tirapazamine; Treatment Outcome; Triazines; Tumor Cells, Cultured

Tirapazamine is a hypoxic cytotoxin currently undergoing Phase II/III clinical evaluation in combination with radiation and chemotherapeutics for the treatment of non-hematological cancers. Tissue penetration studies using multicellular models have suggested that tirapazamine exposure may be limited to cells close to blood vessels. However, animal studies show tirapazamine enhances the anti-tumour activity of radiation and chemotherapy and clinical studies with tirapazamine, so far, are promising. To investigate this apparent paradox we examined the microregional effects of tirapazamine in vivo by mapping drug effects with respect to the position of blood vessels in tumour cryosections.. Tirapazamine was administered i.p. to mice bearing HCT-116 tumours, which were excised at various times after treatment. Images of multiple-stained cryosections were overlaid to provide microregional information on the relative position of proliferating cells, hypoxia, perfusion and vasculature.. We observed extensive and permanent vascular dysfunction in a large proportion of tumours from mice treated with tirapazamine. In the affected tumours, blood flow ceased in the centrally located tumour vessels, leaving a rim of functional vessels around the periphery of the tumour. This vascular dysfunction commenced within 24 h after tirapazamine administration and the areas affected appeared to be replaced by necrosis over the following 24-48 h.. Because the majority of hypoxic cells are located in the center of tumours we propose that the activity of tirapazamine in vivo may be related to its effects on tumour vasculature and that its activity against hypoxic cells located distal to functional blood vessels may not be as important as previously believed.

Topics: Animals; Antimetabolites; Antineoplastic Agents; Blood Vessels; Bromodeoxyuridine; Cell Hypoxia; Cell Proliferation; Coloring Agents; Female; HCT116 Cells; Humans; Image Processing, Computer-Assisted; Immunohistochemistry; Mice; Mice, Inbred NOD; Mice, SCID; Necrosis; Platelet Endothelial Cell Adhesion Molecule-1; Regional Blood Flow; Skin Neoplasms; Tirapazamine; Transplantation, Heterologous; Triazines

We clarified the usefulness of the continuous administration of tirapazamine (TPZ) in combination with reduced dose-rate irradiation (RDRI) using gamma-rays or reactor thermal neutrons. Squamous cell carcinoma (SCC) VII tumour-bearing mice received a continuous administration of 5-bromo-2'-deoxyuridine (BrdU) to label all proliferating (P) cells. Then, they received a single intraperitoneal injection or 24 h continuous subcutaneous infusion of TPZ in combination with conventional dose-rate irradiation (CDRI) or RDRI using gamma-rays or thermal neutrons. After irradiation, the tumour cells were isolated and incubated with a cytokinesis blocker, and the micronucleus (MN) frequency in cells without BrdU labelling ( = quiescent (Q) cells) was determined using immunofluorescence staining for BrdU. The MN frequency in the total tumour cells was determined using tumours that were not pre-treated with BrdU. The sensitivity of both total and Q cells, especially of Q cells, was significantly reduced with RDRI compared with CDRI. Combination of TPZ increased the sensitivity of both populations, with a slightly more remarkable increase in Q cells. Furthermore, the continuous administration of TPZ raised the sensitivity of both total and Q cell populations, especially the former, more markedly than the single administration, whether combined with CDRI or RDRI using gamma-rays or thermal neutrons. From the viewpoint of solid tumour control as a whole, including intratumour Q-cell control, the use of TPZ, especially when administered continuously, combined with RDRI, is useful for suppressing the reduction in the sensitivity of tumour cells caused by the decrease in irradiation dose rate in vivo.

Topics: Animals; Bromodeoxyuridine; Carcinoma, Squamous Cell; Cell Survival; Fluorescent Antibody Technique; Gamma Rays; Hyperthermia, Induced; Infusions, Parenteral; Mice; Mice, Inbred C3H; Micronucleus Tests; Neoplasm Transplantation; Neutrons; Radiation-Sensitizing Agents; Radiotherapy Dosage; Skin Neoplasms; Tirapazamine; Treatment Outcome; Triazines