Improvement of the Tumor-Suppressive Effect of Boron Neutron Capture Therapy for Amelanotic Melanoma by Intratumoral Injection of theTyrosinaseGene

Boron neutron capture therapy (BNCT) is successful when there is a sufficient (10)B concentration in tumor cells. In melanoma, (10)B-para-boronophenylalanine (BPA) accumulation is proportional to melanin-producing activity. This study was done to confirm enhancement of the tumor-suppressive effect of BNCT on amelanotic melanoma by intratumoral injection of the tyrosinase gene. D178 or FF amelanotic melanomas were implanted s.c. in Syrian hamsters. One group of D178- or FF-bearing hamsters (TD178 or TFF group) received intratumoral injections of pcDNA-Tyrs constructed as a tyrosinase expression plasmid. The other hamsters (pD178 and pFF groups) were injected with pUC119, and control hamsters (D178 and FF groups) only with transfection reagents. All the groups underwent immunofluorescence analysis of tyrosinase expression and BPA biodistribution studies. BNCT experiments were done at the Kyoto University Research Reactor. Tyrosinase expression increased in the tumors of the TD178 and TFF groups but remained the same in the pD178 and pFF groups. Tumor boron concentrations in the TD178 and TFF groups increased significantly (TD178: 49.7 +/- 12.6 versus D178: 27.2 +/- 4.9 microg/g, P < 0.0001; TFF: 30.7 +/- 6.6 versus FF: 13.0 +/- 4.7 microg/g, P < 0.0001). The BNCT tumor-suppressive effect was marked in the TD178 and TFF groups. In vivo transfection with the tyrosinase gene increased BPA accumulation in the tumors, the BNCT tumor-suppressive effect on amelanotic melanoma being significantly enhanced. These findings suggest a potential new clinical strategy for the treatment of amelanotic melanoma with BNCT.

A primary amelanotic melanoma of the vagina, diagnosed by immunohistochemical staining with HMB-45, which recurred as a pigmented melanoma

Usually, malignant melanoma is readily diagnosed by the presence of melanin granules. Although amelanotic melanoma contains a few melanin granules, it is often difficult to differentiate from non-epithelial malignant tumours. This report describes a case of amelanotic melanoma of the vagina, which was originally suspected to be a non-epithelial malignant tumour, but was subsequently correctly diagnosed by immunohistochemical staining with the HMB-45 antibody and for the S-100 protein. A light grey tumour with superficial ulceration was located in the upper third of the vagina. The patient was treated with irradiation followed by chemotherapy. Subsequently, the tumour disappeared and cytology was negative; thus, she achieved complete remission. However, 20 months after complete remission, the tumour recurred locally: the site had a grossly black appearance, which was pathognomonic for a malignant melanoma. Thus, HMB-45 and S-100 protein immunohistochemistry confirmed the diagnosis of amelanotic melanoma.

Effect of boron neutron capture therapy for melanotic and amelanotic melanoma transplanted into mouse brain

In order to develop a protocol to treat brain metastatic melanoma using our 10B-p-boronophenylalanine (BPA) boron neutron capture therapy (BNCT), we initiated the following studies (i), Comparative analyses of boron biodistribution between melanoma proliferating in the brain and skin among melanotic and amelanotic types, and (ii) Therapeutic evaluation of BPA-BNCT for brain melanoma models of both types, using survival times. Our present data have revealed that boron concentration in melanoma proliferating in the brain, the major prerequisite for successful BNCT, showed a positive correlation to melanin synthesizing activity in the same way as melanoma proliferating in skin. Further, the boron concentration ratio of melanoma to normal surrounding tissue for brain melanoma models was considerably higher than that for subcutaneous (s.c.) ones because of the existence of the blood-brain barrier (BBB). Additionally, from analyses of median and mean survival times following BNCT using low, middle, and high neutron doses, the therapeutic effect of BNCT for the amelanotic A1059 melanoma appeared at first glance to be higher than that for the highly BPA attracting and highly relative biological effect equivalent dose obtaining B15b melanoma. As the survival time was dependent on both regression and regrowth curves, and because the brain melanoma model in small animals made it difficult to evaluate these curves separately, we further examined the in vivo growth curve of both types of melanomas following implantation in s.c. tissue. The melanotic B15b melanoma was indeed found to possess much higher growth rate as compared with that of the amelanotic A1059 melanoma. The significance of boron biodistribution studies and BNCT survival curve analyses in forming an effective clinical protocol for individual human cases of melanoma brain metastasis is discussed.

Experimental ruthenium plaque therapy of amelanotic and melanotic melanomas in the hamster eye

The effects of beta-radiation on melanoma implanted into the hamster's eye were investigated. Two Bomirski hamster melanomas (BHMs), differing in their melanin content, were compared with regard to their radiosensitivity to ruthenium-106 (106Ru) radiation. Tumours growing in the iris were irradiated with 3, 6 or 10 Gy of 106Ru given as a single dose or in four fractions at 24 h Intervals. Tumour growth kinetics and distant metastases were studied, and the eyeballs were examined histologically. Dose-dependent delay of tumour growth was observed in both melanomas. After treatment with a dose of 6 Gy, the Ab amelanotic tumours grew 2.6 times slower, and the Ma melanotic tumours 1.4 times slower than untreated ones. The location of metastases differed in the two tested lines--pigmented metastases were found mainly in the lungs, while unpigmented metastases were found mainly in the kidneys. Histopathological analysis showed signs of blood vessel damage such as endothelial cells swelling, erythrocyte extravasation and tumour necrosis. This last finding increased with the rising dose of beta-radiation. Pigmented tumours were found to be two times more resistant to beta-radiation than amelanotic ones. The pattern of metastases of BHMs is determined by the type of melanoma (Ab or Ma). Exposure to beta-radiation from 106Ru did not significantly affect either the number or size of metastases except at a dose of 10 Gy. This dose caused a statistically significant decrease in the number of metastases in the Ma melanotic subline.

Monitoring of tumor reoxygenation following irradiation by 31P magnetic resonance spectroscopy: an experimental study of human melanoma xenografts

BACKGROUND AND PURPOSE

Inadequate tumor reoxygenation during radiation therapy may cause local treatment failure. This study was aimed at investigating the potential usefulness of 31P-MRS in monitoring tumor reoxygenation following radiation treatment.

MATERIALS AND METHODS

Tumors of two human melanoma xenograft lines (BEX-t and HUX-t) were exposed to 15.0 Gy, and then the fraction of radiobiologically hypoxic cells, measured by using the paired survival curve method, or tumor bioenergetic status, measured by 31P-MRS as the (PCr + NTPbeta)/Pi resonance ratio, was determined versus time after the radiation exposure.

RESULTS

Untreated BEX-t and HUX-t tumors showed similar fractions of radiobiologically hypoxic cells and similar bioenergetic status, whereas both parameters differed substantially between the lines in irradiated tumors. A close association was found between radiation-induced changes in tumor bioenergetic status and radiation-induced changes in the fraction of radiobiologically hypoxic cells.

CONCLUSION

31P-MRS is a potentially useful method for monitoring tumor reoxygenation following radiation treatment.

Choroidal metastasis in men with metastatic breast cancer

PURPOSE

To report two cases of choroidal metastasis in metastatic breast cancer in men.

METHOD

Case reports of a 50-year-old man with an 8-year history of breast cancer who was initially examined with a solitary amelanotic choroidal tumor and a 62-year-old man with an 8-month history of breast cancer who was initially examined with numerous unilateral amelanotic choroidal tumors.

RESULTS

Ophthalmoscopic and echographic characteristics of the choroidal tumors were typical for breast cancer metastasis. Systemic screening disclosed advanced metastatic disease in both patients. Choroidal metastasis could be effectively treated by external beam irradiation.

CONCLUSIONS

Although breast cancer is a rare condition in men, it should be considered as a possible primary cancer in cases of choroidal metastasis.

Enhanced melanogenesis induced by tyrosinase gene-transfer increases boron-uptake and killing effect of boron neutron capture therapy for amelanotic melanoma

Specific and powerful cancer killing effect for melanoma by boron neutron capture therapy (BNCT) using DOPA analogue, 10B-p-boronophenylalanine (10B-BPA), has been established, but amelanotic melanoma is insufficiently responsive to 10B-BPA BNCT in comparison with actively melanin-producing melanoma. Although the accumulation mechanism of 10B-BPA within melanoma was not established, we have recently obtained findings suggesting that melanin monomers, key intermediates for melanin polymer formation, play a critical role in 10B-BPA accumulation. In addition, there are some kinds of human amelanotic melanomas, such as MEL2A, in which expression of tyrosinase is repressed or lacking though tyrosinase-related protein (TRP)-1 and TRP-2 are well expressed. Thus, by using a similarly tyrosinase-lacking mouse amelanotic melanoma cell line, A1059, we constructed TA1059 cells by transfecting human tyrosinase-cDNA into these cells. TA1059 cells acquired higher DOPA-oxidase and DOPAchrome tautomerase activity as well as eumelanin content at even higher levels than those of B16F10 cells. TA1059 cells showed about 2.5 times higher P-boronophenylalanine (BPA) uptake than A1059 cells in culture. In animal experiments, by using these cell lines, tumor growth of TA1059 was significantly suppressed by 10B-BPA BNCT as compared with A1059. These findings indicate that the induction of active melanin biosynthesis by melanogenic gene-transfer effectively improves the treatment of amelanotic melanoma by BNCT.

[Choroid melanoma associated with 2 other primary malignant lesions. Apropos of a case]

A case of choroidal melanoma associated to two other primitive malignancies is reported. The patient, a 65-year-old woman had an amelanotic choroidal tumor of her left eye. In her clinical history was found a previously treated kidney carcinoma eight years ago. A choroidal metastasis was therefore diagnosed. After radiation therapy, an initial regression was observed. Fifteen months later, the tumor grew again. Enucleation was performed, and histopathology concluded on choroidal malignant melanoma. Three years later, a mammal carcinoma was discovered and treated by mammectomy. Her ophthalmologic and general status remained normal until now. Amelanotic choroidal tumors are difficult to diagnose. Regular follow-up can lead to a change in the diagnosis. The occurrence of multiple cancers is still not fully understood.

Visualization of uveal amelanotic melanoma with technetium-99m(V) dimercaptosuccinic acid

The possibility of using technetium-99m(V) dimercaptosuccinic acid, Tc-99m DMSA, in the evaluation of uveal amelanotic melanoma was assessed in this study. Both planar and SPECT images clearly demonstrated the tumor. Following confirmation of our results by contemporaneous ultrasonography and MRI the patient was treated with Iodine-125 brachytherapy. In combination with other diagnostic tests, Tc-99m(V) DMSA scintigraphy may play a role in the detection of uveal melanoma and its possible systemic metastases.

Oral malignant melanoma in Japan

Clinical examination was performed on 20 cases of malignant melanoma in the oral region encountered at the First Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Tokyo Medical and Dental University, during the 22-year period from 1970 to 1991. In addition, we reviewed 140 cases reported in the Japanese literature since the last major review in 1974. The results of our study revealed that the clinical course of malignant melanoma in the oral region is worse than oral squamous cell carcinoma and that treatment by radiotherapy is effective in prolonging the life of these patients. Clinically, the tumors were classified into five types: (1) pigmented nodular type; (2) nonpigmented nodular type; (3) pigmented macular type; (4) pigmented mixed type; and (5) nonpigmented mixed type. We suggest that oral malignant melanoma might be different from cutaneous malignant melanoma and that new criteria for diagnosis and therapy for oral disease should be considered.

Validity and usefulness of human tumor models established by intratibial cell inoculation in nude rats

Intratibial injection in nude rats of 1 x 10(6) OHS, MHMX, and LOX human tumor cells resulted in each case in progressively growing bone tumors. When the diameter of the affected leg had increased by 2-3 mm, the animals were examined for uptake of 99mTc-methylenediphosphonate. The OHS osteosarcoma tumors caused sclerotic lesions with high and uniform isotope uptake, and the MHMX unclassified sarcoma showed a mixed pattern with both sclerotic and lytic areas, whereas the LOX melanoma caused lytic bone lesions with low uptake of the radionuclide. These findings were compared with the results of analogous investigations previously performed in the patients from whom the tumor lines originated. Striking similarities in both the morphology and the scintigraphic images were observed between corresponding tumors in rats and humans, with results supporting the clinical relevance of the model systems. When the LOX model was used for therapy experiments, doxorubicin had no effect on the growth of the tibial tumors, which in the control group appeared after a latency of 13.5 days. The alkylating agent mitozolomide increased the median tumor-free latency to 47 days in 7 rats, and 5 animals did not develop tumors within the observation period of 60 days. Doxorubicin was ineffective also against the OHS tumor, whereas ifosfamide and the radionuclide 89Sr-chloride showed significant antitumor activity. The disease-free latency increased from 20 days, in the control animals, to 45 and 28.5 days, respectively, in the 2 treated groups, in which 2 of 7 and 2 of 10 rats were without tumors at 60 days. The data demonstrate that the tibial models discriminated between the action of the different therapeutic agents, and suggest that they may be useful in selecting compounds with clinical activity against skeletal tumors.