Pigmented Nevi and Malignant Melanomas as Studied with a Specific Fluorescence Method

Concept of a fully-implantable system to monitor tumor recurrence

Current treatment for glioblastoma includes tumor resection followed by radiation, chemotherapy, and periodic post-operative examinations. Despite combination therapies, patients face a poor prognosis and eventual recurrence, which often occurs at the resection site. With standard MRI imaging surveillance, histologic changes may be overlooked or misinterpreted, leading to erroneous conclusions about the course of adjuvant therapy and subsequent interventions. To address these challenges, we propose an implantable system for accurate continuous recurrence monitoring that employs optical sensing of fluorescently labeled cancer cells and is implanted in the resection cavity during the final stage of tumor resection. We demonstrate the feasibility of the sensing principle using miniaturized system components, optical tissue phantoms, and porcine brain tissue in a series of experimental trials. Subsequently, the system electronics are extended to include circuitry for wireless energy transfer and power management and verified through electromagnetic field, circuit simulations and test of an evaluation board. Finally, a holistic conceptual system design is presented and visualized. This novel approach to monitor glioblastoma patients is intended to early detect recurrent cancerous tissue and enable personalization and optimization of therapy thus potentially improving overall prognosis.

Quantitative measurements of formalin-induced fluorescence for differential diagnostics of melanomas and lesions of human skin

The usefulness of formaldehyde-induced fluorescence (FIF) for detection of melanoma cells has been suggested by several investigators during the last 40 years. FIF can be easily excited and observed in microscopic sections of formalin-fixed paraffin-embedded skin samples. However, such an approach has never been widely used in melanoma diagnostics for reasons including lack of clear diagnostic criteria, considerable inconsistencies in both the protocols used and qualitatively analysed results reported by different groups. This study aimed at determination of the spectral bands optimum for detecting melanoma cells. The study involved three sets of the excitation and emission bands: gammaex=366 nm, gammaem>425 nm; gammaex=450-480 nm, gammaem>515 nm; gammaex=450-480 nm, gammaem=510-550 nm. Microscopic digital imaging was used to quantitatively determine the fluorescence intensity of 53 primary melanomas and 32 benign lesions. Best classification of melanomas with algorithm based on fluorescence intensity threshold was obtained for gammaex=450-480 nm, gammaem=510-550 nm. Receiver operating characteristics (ROC) analysis of the algorithm yielded area under the curve=0.84 +/- 0.05 for melanocytic cells present in the stratum corneum. Our results clearly indicate that the FIF emitting molecules (most probably 5-S-cysteinyldopa) are present in melanomas at the concentration significantly higher than in benign lesions. In terms of the ROC analysis, the diagnostic performance of the test based on the FIF intensity is as good as of many other commonly used diagnostic tests.

The Pigmented Life of a Redhead

As a redhead I have had a personal interest in red hair, freckles and sunburns since childhood. An observation of a formaldehyde-induced fluorescence in human epidermal melanocytes initiated my scientific interest in these cells. Prota and Nicolaus demonstrated that oxidation products of cysteinyldopas are the main components of pheomelanin. Our identification of 5-S-cysteinyldopa as the source of formaldehyde-induced fluorescence of normal and pathological melanocytes started a series of investigations into this amino acid, enzymatic and non-enzymatic oxidation of catecholic compounds and the metabolism of thiols. All melanocytes with functioning tyrosinase produce cysteinyldopas and the levels of 5-S-cysteinyldopa in serum and urine are related to the size and pigment forming activity of the melanocyte population. The determination of 5-S-cysteinyldopa in serum or urine is a sensitive diagnostic method in the detection of melanoma metastasis. Some non-specific formation of cysteinyldopa is present in the body, as demonstrated by 5-S-cysteinyldopa in individuals with tyrosinase-negative albinism.

Autofluorescence of melanins induced by ultraviolet radiation and near ultraviolet light. A histochemical and biochemical study

The induction of autofluorescence of melanins by UV radiation (330-380 nm) and near UV (400-440 nm) light (jointly called UV light) was studied in tissue sections using three commercially available mounting media. Only Immu-Mount (Shandon) was found suitable for this purpose. UV irradiation of melanins in sections mounted in this medium induced strong yellow autofluorescence irrespective of the type of the polymer (eumelanin, neuromelanin, pheomelanin and ochronotic pigment). The phenomenon of autofluorescence induction was also observed with isolated natural and in vitro prepared melanins. It was inhibited by anhydrous conditions, sodium azide and catalase. In parallel experiments, rapid degradation of melanins with an intermediate fluorescent stage was achieved in UV-irradiated sections mounted in media artificially enriched with hydrogen peroxide, or directly in aqueous solutions of H2O2, Na2O2 or HIO4. Oxidations not associated with UV light led to nonfluorogenic breakdown of melanins. These observations indicate that the common mechanism may be an oxidative attack resulting from a concerted action of hydrogen peroxide and UV light leading, through strongly fluorescent intermediates, to a complete bleaching and oxidative breakdown of melanin and melanin-like polymers. Reactive oxygen species (including ozone) are considered to be important reactants in these experiments. Lipopigments differ from melanin-like pigments by their primary autofluorescence, which mostly faded during continuous prolonged irradiation. The only regular exception was melanosis coli pigment, the autofluorescence of which was considerably augmented by UV irradiation. Our results demonstrate a novel type of fluorogen in autofluorescent pigment histochemistry. The implications of the results are discussed especially in the light of the possible presence of melanin-based fluorogens in lipopigments.

Hyperpigmentation and hypopigmentation of the skin after long term PUVA therapy. Light and electron microscopic observations on three patients

An electron microscopic study was performed to demonstrate the pathological changes induced by long term PUVA treatment in recalcitrant psoriasis. Three patients developed mottling (hyperpigmentation and hypopigmentation) during two to three years of treatment. Three different types of morphological changes were found: disarrangement of keratinocytes, clustering and stimulation of melanocytes and homogenization of papillary dermis. Furthermore, the superficial blood vessels were loaded with the same type of amorphous granular substance. These changes might be specific to PUVA treatment or they might occur only in patients with previous treatment with, e.g., arsenic, methotrexate, anthralin + UVB or a combination of these.

Formaldehyde-fluorescamine-induced fluorescence as a property of carcinoma cells

Fluorescamine is a sensitive cytochemical probe for primary amino groups and produces an intense general fluorescence in unfixed tissue sections reflecting the ubiquitous occurrence of such groups. Following treatment with formaldehyde, most primary amino groups react to form derivatives unable to yield fluorescence with fluorescamine. Certain cell systems, however, contain amino groups which do not react with formaldehyde but display strong reactivity with fluorescamine. In formaldehyde- and fluorescamine-treated specimens such cell systems display an intense fluorescence, whereas the majority of tissue constituents are non-fluorescent. Fluorescent cell systems include certain protein- and peptide-secreting cells and a large number of different types of carcinoma cells. In some cases it appears that neoplastic transformation is necessary before the cells display formaldehyde-fluorescamine-induced fluorescence. Available data indicate that the reactive substance(s) are peptide in nature and that the production of such substance(s) may be a general property of carcinoma cells.

Normal and malignant melanin-containing pigment cells of xiphophorine fish as studied with formaldehyde-induced fluorescence

Embryonic skin and eyes, and melanomas of xiphophorine fish were investigated by fomaldehyde-induced fluorescence in order to test whether the pigment cells in these tissues may be identified by a specific green-yellow fluorescence. Skin of pigmented fish embryos showed no fluorescence in the black pigment cells (melanocytes and melanophores), while skin of albino embryos showed a green-yellow fluorescence in all cells which correspond to the black pigment cells of pigmented embryos. The skin of both pigmented and albino embryos showed a bright orange fluorescence in the red pigment cells (pterinophores). No fluorescence was observed in the retinal pigment epithelium of pigmented embryos, while a green-yellow fluorescence was observed in the pigment epithelium of albino embryos. Neither the melanotic melanomas of pigmented fish nor the amelanotic melanomas of albino fish showed any specific fluorescence.

Ocular melanomas: formaldehyde-induced fluorescence in relation to mortality

Some ocular malignant melanomas contain enough cysteinyldopa to make them fluorescent when treated with formaldehyde. In 32 ocular malignant melanomas, such fluorescence was seen in 19 cases, which had a slightly, but not significantly, worse prognosis than the 13 cases with no fluorescence. The mixed type of malignant melanoma showed fluorescence significantly more often than the B type. Fluorescence histochemistry thus gives a biochemical classification of the tumor, but not a malignancy prognosis.

Fluorescence histochemical demonstration of dopa thioethers by condensation with gaseous formaldehyde

The usefulness of the formaldehyde (FA) and glyoxylic acid (GA) methods for the fluorescence histochemical demonstration of dopa thioethers has been tested using protein droplet models. Similar fluorescence intensities were recorded from these compounds after either FA or GA treatment. Cysteinyldopa gave a high fluorescence yield similar to that obtained from dopamine and dopa in the FA reaction, whereas gluatitodopa showed a lower, although clearly visible fluorescence. Since the FA method seemed to be the most useful one for demonstration of catechol thioethers, the FA-induced fluorophores of these compounds were further characterized by microspectrofluorometry. The spectral characteristics of the thioether fluorophores (excitation maxima at 420 nm and emission maxima at 480-485 nm) distinguish these substances from dopa and other compounds fluorogenic in the Falck-Hillarp method. Dopa thioethers are proposed to form fluorophores with FA in a manner analogous to that of the primary catecholamines i.e. via low-fluorescent tetrahydroisoquinolines, along two different pathways, to strongly fluorescent 3,4-dihydroisoquinolines and 2-methyl-dihydroisoquinolinium compounds. These dihydroisoquinolines are in a pH-dependent tautomeric equilbrium with their quinoidal forms as reflected by a characteristic spectral shift upon acidification. The results of this study provide the guide-lines for the characterization of fluorogenic compounds in pigment-forming cells.

On the occurrence of cysteinyldopa and dopa in melanocytes and benign nevi cells

Previous studies have demonstrated a specific cytoplasmic fluorescence in human melanocytes, as well as in pigmented nevi and in malignant melanomas, when the formaldehyde histofluorescence method for visualization of certain catechol and indole derivatives was used. In malignant melanoma two fluorogenic substances, dopa and cysteinyldopa, were found previously. In human melanocytes and benign nevi cells the fluorogenic catechols have so far not been characterized, since chemical analyses are difficult to perform on skin, due to the small amounts of catechols present. However, using split thickness skin quantitative determinations are possible by sensitive fluorometric methods. The chemical analyses of cysteinyldopa showed that in human adult skin most or all was located in the superficial layers. The only specific fluorescence in the thin skin was found in dendritic melanocytes. The findings leave little doubt that cysteinyldopa is stored in melanocytes although the possibility of a concomitant occurrence of other thioethers is not excluded. Nevi and giant nevi were also similarly studied and we found considerable amounts of cysteinyldopa in the nevi. It seems as if the cysteinyldopa is stored in the fluorescent nevi cells. There was no consistent difference in the content of the catechol derivatives between intradermal and compound nevi.

[Fluorescence histochemical and microfluorometrical investigations of pigmentary tumors of the skin (author's transl)]

Junction nevus, dermal nevus, melanosis circumscripta praecancerosa Dubreuilh, superficial spreading melanoma, and nodular melanoma were investigated and characterized by use of the formalin induced fluorescence method (FIF). In the vicinity of junctional nevus cell clusters and near tumor cells of the superficial spreading melanoma increased numbers of melanocytes are found. These show different types of dendritic branching. Spherical nevus cells however are completely devoid of dendritic processes. On the other hand, the atypical pigment cells in melanosis circumscripta praecancerosa Dubreuilh exhibit a shape similar to that of melanocytes, whereas the globular cells of superficial spreading melanoma have the appearance of nevus cells. The arrangement of nodular melanoma cells resembles that observed in dermal nevus. However the characteristic decrease in fluorescence intensity from epidermal junction to deeper dermis as observed in the dermal nevus was missed in nodular melanomas. Dendritic pigment cells displaying formalin induced fluorescence (FIF) could be demonstrated in all types of malignant melanomas investigated in the present study. The fluorophores of the pigment lesions are characterized microspectrofluorimetrically by (1) ill-defined emission maxima between 470 and 490 nm and (2) a clear-cut excitation maximum at 430 nm accompanied by a lower one at 320 nm. Hydrochloric acid vapor induces a hyposochromic shift of the 430 nm excitation maximum to 370-380 nm and a marked elevation of the 320 nm maximum. These results indicate fluorophores of DOPA and its derivatives; in this respect there are no marked differences between melanocytes, nevus cells and the cells of malignant melanoma.