Systemic photodynamic therapy with aminolaevulinic acid delays the appearance of ultraviolet-induced skin tumours in mice

BACKGROUND

Photodynamic therapy (PDT) with topical aminolaevulinic acid (ALA) has recently been approved by the US Food and Drug Administration for the treatment of actinic keratoses.

OBJECTIVES

To determine whether weekly systemic suberythemogenic ALA-PDT could prevent the appearance of ultraviolet (UV) -induced skin tumours in hairless mice.

METHODS

One group of 20 mice received daily UV radiation from FS 20 tubes, and weekly intraperitoneal injections of ALA 40 mg kg(-1), each followed 3 h later by 12 J cm(-2) of white light (ALA-PDT). Control groups consisted of mice exposed only to UV, to UV and ALA without white light, or UV and white light without ALA, as well as untreated mice.

RESULTS

The tumour-free survival was significantly longer for mice exposed to daily UV and weekly ALA-PDT as compared with the control groups. Neither the mortality nor the incidence of large skin tumours was higher in the UV/ALA-PDT group than in mice exposed only to UV. In vivo fluorescence spectroscopy showed that the 635-nm fluorescence emission within tumours was lower than in normal skin 3 h after ALA administration. This was also confirmed by quantitative fluorescence microscopy.

CONCLUSIONS

Systemic ALA-PDT can delay the appearance of UV-induced skin tumours in mice without increasing mortality or the incidence of large tumours.

In situ distribution of integrin alpha 2 beta 1 and alpha-actinin in melanocytic proliferations

Integrin alpha 2 beta 1 is a transmembrane protein receptor for collagen and laminin previously reported as a melanoma tumor progression antigen. alpha-Actinin is an actin-binding protein reported to interact with the cytoplasmic domain of the beta 1-integrin chain of alpha 2 beta 1. In vitro, both alpha 2 beta 1 and alpha-actinin play a role in melanoma cell motility. In turn, increased melanoma cell line motility (measured as mean migration rates), correlates with metastasis. To determine the in situ distribution of these proteins, we used monoclonal antibodies directed against the alpha 2-integrin subunit of alpha 2 beta 1 and alpha-actinin on frozen sections of 33 melanocytic proliferations, which included dermal nevi, primary melanomas, and metastatic melanomas. We found that the superficial portion of all of the melanocytic proliferations tested stained for alpha-actinin. In benign nevi and superficial spreading melanoma, there was a notable loss of staining for alpha-actinin in the cells in the deep reticular dermis. In contrast, alpha-actinin was present on almost all of the tumor cells in the nodular melanomas and the melanoma metastases. Tumors stained either uniformly positive or uniformly negative for alpha 2 beta 1; the expression of this protein correlated with the later stages of melanoma progression. Our findings suggest that alpha-actinin protein levels initially decrease and then increase during melanocytic tumor progression, whereas the alpha 2 subunit protein appears in the later stages of melanoma progression. The variable distribution of these proteins is evidence for the differential adhesive and motile properties of subpopulations of cells in melanocytic proliferations.

Histologic spectrum of cutaneous involvement in patients with myelogenous leukemia including the neutrophilic dermatoses

BACKGROUND

Cutaneous manifestations of myeloid leukemia can be specific or nonspecific. The study was designed to determine the prevalence and histologic appearance of cutaneous lesions in patients with myeloid leukemia and various myeloproliferative disorders.

METHODS

The histologic changes of cutaneous lesions in 52 patients with myelodysplastic syndrome, polycythemia vera, and myeloid, myelomonocytic, or monocytic leukemia are presented in this study.

RESULTS

Two types of cellular infiltrates were identified. In the first group, the most common pattern was a diffuse involvement by the leukemic cells through the entire dermis with preservation of a "grenz zone" in the superficial dermis. Two cases exhibited a Kaposi's sarcoma-like pattern, with prominent slit-like blood-filled spaces lined by myeloblasts against a fibrocellular stroma. The second group of lesions was characterized by dense, neutrophilic dermal infiltrates resembling acute neutrophilic dermatosis (Sweet's syndrome) or pyoderma gangrenosum. In two of these cases, scattered immature blast cells admixed with the mature neutrophilic elements were identified.

CONCLUSIONS

Awareness of these different morphologic features and application of special stains are of value in the evaluation of suspicious cutaneous infiltrates in patients with myeloid leukemia and various myeloproliferative disorders.

Actin-binding protein expression in benign and malignant melanocytic proliferations

Studies on melanoma cell lines indicate the expression of actin-binding protein (ABP), a peripheral cytoplasmic protein that crosslinks actin, is important for melanoma cell motility. We used an ABP-specific monoclonal antibody to characterize ABP expression in 18 benign nevi and 28 primary and metastatic malignant melanomas. Heterogeneous expression of ABP staining was observed in metastatic melanoma. No clear differences in ABP staining were identified among compound nevi, dysplastic nevi, and superficial spreading melanoma; however, the lentiginous intraepidermal component of the benign and malignant lesions and the pagetoid cells of superficial spreading malignant melanoma were negative for ABP. In contrast, the nested intraepidermal and dermal components of both benign nevi and primary malignant melanoma were positive. The differential expression of ABP of the lentiginous component as opposed to the intraepidermal nests and pagetoid cells of benign nevi or melanoma may represent a capacity of the nested melanocytes to migrate from the epidermis to the dermis during maturation or invasion. Taken together, the findings support that ABP may be important for cell-cell adhesion during tumorigenesis and may play a role in tumor cell ameboid motility during tissue invasion.

Very late metastasis (27 years) of cutaneous malignant melanoma arising in a halo giant congenital nevus

We report a case of primary cutaneous melanoma with the incidental finding of a lung metastasis 27 years following the original diagnosis. The case is exceptional in that it is a late metastasis of a melanoma that arose in association with a halo giant congenital nevus. The original tumor was a large dermal/subcutaneous nodule composed of very well-differentiated cells reminiscent of type B nevomelanocytes. The metastasis displayed similar histology. This case emphasizes the unpredictable behavior of malignant melanoma. In cases with 'unusual' histology such as this one, the usual prognostic parameters are less helpful in predicting survival. Melanoma should be included in the differential diagnosis of an undiagnosed lesion suspicious for metastasis even if the primary was removed in the remote past.