BNL-6 4 136

International Congress on Photobiology, Vienna, Austria, September 1-6, 1996 ~ Action Spectrum for Melanoma Induction i n Hybrid Fish o f the Genus Xiphophorus

Richard B. Setlow Biology Department Brookhaven National Laboratory Upton, NY 11973 USA

I 1. - Introduction

Cutaneous ma l i gnant me1 anoma (CMM) i s a compl i cated d i sease tha t i s dependent

on a number o f factors tha t influence i t s incidence i n ways that are quant i ta t ive ly

uncertain (1). Such factors include genetic background, including sk in type and ha i r

color, and the presence and d is t r ibu t ion o f nevi, and l i f e s t y l e habits such as sun

exposures- -where, t i m e o f day and year, frequency, intensi ty, use o f sunscreens etc.

A common denominator i s sun exposure, as best indicated by a comparison i n Austral ia

o f CMM on exposed body areas vs. sun protected s i tes- -96-97% on exposed s i tes - - , and

from a comparison o f the incidence rates i n the U.S. o f CMM i n whites compared t o

blacks- -92-96% among whites (2). CMM i s not a disease o f outdoor workers and it

d i f f e r s from non melanoma skin cancer i n tha t i t i s associated wi th episodic

exposures rather than chronic ones. LN 0

CMM i s a publ ic health concern because i t s incidence, among whites, has been

increasing a t the ra te o f 4-5% per year fo r approximately 50 years (3) so tha t t h i s cn 'I

once very rare disease i s now (excluding non-melanoma skin cancer) the 4th most

common cancer i n Austral ia and New Zealand and the 10th most common one i n the U.S. 0 a

The incidence o f CMM increases w i th proximity t o the Equator- -an observation i n

l i n e wi th the conclusion tha t sun exposure i s the most important e t io log ic agent. I

However, the l a t i t ude e f fec t does implicate UVB because the in tens i t ies o f a l l

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liabili- ty or responsibility for the accuracy, completeness, or usefulness of any information, appa- ratus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessar- ily state or reflect those of the United States Government or any agency thereof.

spectral regions increase toward the Equator. An understanding o f the useful pub1 i c

health measures t o lower the incidence o f CMM would benefi t g rea t ly i f the spectral

region o f sun1 i ght imp1 i cated i n me1 anoma i nci dence were known. Such know1 edge

requires animal models t o evaluate the incidence as a function o f wavelength. There

are marsupial models, a transgenic mouse model, and a f i s h model (5). To date, only

the f i s h model has been employed t o obtain an action spectrum (6.7).

The fac t t h a t xeroderma p i gmentosum i ndi v i dual s - -def i c i ent i n DNA repai r - - have

a prevalence o f CMM tha t i s several thousand-fold greater than i n the normal

population (8) i s an indicat ion tha t DNA i s a target f o r l i g h t induced CMM. DNA

absorbs strongly i n the UVB. However, i t i s conceivable tha t melanin i n melanocytes

could absorb energy a t a l l wavelengths and, by an ind i rec t means, a f fec t DNA a t

wavelengths greater than UVB. Again, an animal model would be he lp fu l .

2. A Fish Model

The f i s h model o f Setlow, Woodhead, and Grist (6) uses backcross hybrids o f the

genus XiphoDhorus (X. maculatus (9 ) and X. couchianus (8 ) ) . These hybrids have

melanocytes and are very sensitive t o melanoma induction. Me1 anomas are observed

a f t e r single exposures t o much less than a human minimal erythemal dose o f

monochromatic UV (9). The high sens i t i v i t y i s presumed t o r e f l e c t the presence o f

only a s ingle tumor suppressor gene per melanocyte--approximately lo4 a t the 7 days

o f age when the f i s h are irradiated. Tumors are scored by eye and h i s to log i ca l l y a t

4-6 months. A t each wavelength-302, 313, 365, 405, 436, and 547 nm- -a dose response

curve i s obtained. The i n i t i a l

slopes o f such curves gives the sens i t i v i t y (cross-section i n m2/J converted t o

m2/incident photon) that , normalized t o 1.00 a t 302 nm, gives an act ion spectrum f o r

Figure 1 shows preliminary resul ts f o r 547 nm.

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. .

melanoma induction (Figure 2A). It i s obvious that the melanoma sens i t i v i t y spectrum

i s much higher i n the UVA than the erythemal sens i t i v i t y (10). To obtain the

re la t i ve e f fec t that would be observed i n a sunlight spectrum, the action spectrum

points must be mul t ip l ied by the sunl ight spectrum (Figure 2B).

3. Implications o f the Fish Spectrum

I f the CMM spectrum were simi lar t o the f i s h spectrum, the most e f fect ive

sunl ight inducing wavelength would be i n the UVA region. I n t h i s case, the use o f

sunscreens t o minimize erythema by UVB, o r by UVB plus UVA, could resu l t i n a much

enhanced me1 anoma i nduci ng exposure i f i ndi v i dual s increased the i r exposure t o obtain

a minimum erythemal dose (Table 1).

Table 1 Cal cul ated Re1 a t i ve !el anoma - Induci ng Esposures

from Sun1 igh t Through Sunscreens

No sunscrefn SPF8 (UVB) SPF8 ( U V B / U V ~ ) ~ SPF15 (UVBhva): SPF25 (UVB/uva)

Me1 anoma - Induci ng Exposure Rate

1.00 0.75 0.47 0.65 0.35

Me1 anoma - Induci ny Exposure per MED

1.0 6.0

9.7 3.8

8.7

1. Mid-summer, mid-day, 41". 2. I am indebted t o Brian Di f fey, Medical Physics, Newcastle upon Tyne,

f o r the absorption spectra o f these sunscreens. 3. Minimum erythemal dose. 4. Skin protection factor o f 8, absorption i n the UVB (Diffey). 5. Absorption mostly i n the UVB, but some, dependent on sunscreen

formulation, i n the UVA and a l i t t l e i n the v i s ib le (Di f fey).

Since greater than 90% o f the e f fec t i ve sunlight dose w i th a putat ive CMM

spectrum i s i n the UVA and v i s ib le regions, ozone depletion (af fect ing mostly UVB)

w i 11 be i nconsequenti a1 .

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4. Epidemioloqical Data

There are three types of epidemiological studies t h a t support the important role of UVA i n CMM. 1) The use of sunscreens is associated w i t h a significant risk of

melanoma (11.12). 2) A comparison of the ratio of squamous cell carcinoma (SCC) i n

Australia t o Norway gives a ratio of approximately 20, consistant w i t h the much

higher flux of UVB i n Australia. However, for CMM the ratio is only about 2 (13,141.

Since animal and molecular da ta indicate t h a t UVB is the important spectral region

i n SCC, the UVB cannot be strongly associated w i t h CMM. 3) A role for melanin and

UVA is also supported by the observation of high SCC i n a lb ino African blacks (lots

of UVB) bu t l i t t l e CMM i n this population (lots of UVA bu t no melanin) (15).

An argument against the importance of UVA i n CMM is t h a t mutations observed i n

the CDKN2 gene i n melanoma cell lines derived from human tumors were similar t o those

observed after UVB exposure of cells i n vitro and i n SCC (161, and not similar t o those observed i n mammalian cells exposed t o UVA vitro (17). However, no mutations i n this gene were observed i n the 30 melanoma surgical specimens studied,

indicating t h a t the mutations i n cell lines might be a result of growth i n culture

(18).

I t should be noted t h a t relevant processes other t h a n i n i t i a t i o n may be affected by exposure t o sunlight. For example, immunosuppression i n mice is inhibited by the spectral region, mostly UVB. t h a t forms cyclobutane pyrimidine dimers i n DNA, as

judged by the observation t h a t repair of the dimers by an exogenously applied repair enzyme for dimers minimizes the suppression (19).

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0.1 -

Fig. 1 Preliminary dose-response da ta for melanoma induction by 547 nm.

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Fish Melanoma

:$'c-- 6\ HumanErythema ' - I\[

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300 350 400 450 500 550

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300 350 400 450 500 550 Wavelength (nm)

I ' I 1 I I

Wavelength (nm)

Fig. 2 A) Action spectra (normalized t o 1.00 a, 302 nm) for melanoma induc,ion i n fish and erythema induction i n humans (10). B) The relative sunl ight effective doses (action spectra values multiplied by sun1 ight fluence rate) versus wavelength for fish melanoma and human erythema.

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5. Acknowl edqements

The melanoma data presented here were a co

Avril D. Woodhead, Eleanor Grist, Neva Setlow,

supported i n par t by the Office of Health and

6.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

laborative effort o f the author and

and Keith Thompson. This work was

Envi ronmental Research of the U . S.

Department of Energy.

References

Higginson, J . , Muir. C. S. and Mufioz. N . (1992) "Malignant melanoma" In Human Cancer : Epidemiology and Envi ronmental Causes, Cambridge Uni versi t y Press, Cambridge, U . K . , pp. 365-369

Armstrong, B. K. and Kricker, A. (1993) "How much melanoma is caused by sun exposure?" Me1 anoma Res. 3 : 395 -401

Heston, J . F . , Kelly, J . B., Meigs, J . W. and Flannery. J . T. (1986) "Forty-five years of cancer incidence in Connecticut : 1935- 1979" Natl . Cancer Inst. Monog . 70:347 (updated t o 1989, personal communication)

Armstrong. 6. K. and Kricker, A. (1994) "Cutaneous melanoma" In Trends in Cancer Incidence and Mortality (Doll, R . , Fraumeni, J . F. jr. and Muir. C. S . , eds.) Cold Spring Harbor Press, pp. 219-240

Setlow, R . B. (1996) "Relevance of in models i n melanoma s k i n cancer" Photochem. Photobiol . 63:410-412

Setlow. R. B., Woodhead, A. D. and Grist, E. (1989) "Animal model for ultraviolet radiation-induced melanoma: Platyfish-swordtail hybrid" Proc. Natl . Acad . Sci . USA 86: 8922 - 8926

Setlow, R. B.. Grist, E . , Thompson, K. and Woodhead. A. D. (1993) "Wavelengths effective i n induction of malignant melanoma" Proc. Natl. Acad. Sci. USA 90 : 6666 - 6670

Kraemer, K. H . , Lee, M. M . and Scotto, J. (1984) "DNA repair protects against cutaneous and i nternal neopl asi a : Evidence from xeroderma pi gmentosum" Carci nogenesi s 5 : 511 - 514

Setlow, R. B. and Woodhead, A. D . (1994) "Temporal changes in the incidence of malignant melanoma: Explanation from action spectra" Mutat. Res. 307:365-374

Parrish, J . A . , Jaenicke, K. F. and Anderson, R. R. (1982) "Erythema and me1 anogenesis action spectra of normal human s k i n " Photochem. Photobiol . 36: 187- 191

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11. Autier, P., Dore, J.-F., Schi f f lers. E., Cesarini, J.-P., Bol laerts, A., Koelmel, K. F., Gefeller, O., Liabeuf, A., Lejeune, F., Lienard, D., Joarlette, M., Chemaly, P. and Kleeberg, U. R. (1995) "Melanoma and the use o f sunscreens: An EORTC case-control study i n Germany, Belgium and France" I n t . J. Cancer 61 : 749 - 755

12. Westerdahl, J., Olsson, H., Mdsback, A.. Ingvar. C. and Jonsson, N. (1995) " I s the use o f sunscreens a r i s k factor f o r malignant melanoma" Melanoma Res. 5:59- 65

13. Magnus, K. (1991) "The Nordic p r o f i l e o f skin cancer incidence. A comparative epidemiological study o f the three main types o f skin cancer" I n t . J. Cancer 47: 12 - 19

14. Moan, J. and Dahlback, A. (1993) "Ul t raviolet radiat ion and sk in cancer: Epidemiological data from Scandinavia" I n Environmental UV Photobiology (Young, A. R., Bjarn, L. O., Moan, J. and Nultsch, J., eds.) Plenum Press, New York, pp. 255 - 293

15. Diffey, B. L., Healy. E., Thody, A. 3. and Rees, J. L. (1995) "Melanin me1 anocytes and me1 anoma" The Lancet 346: 1713

16. Pollock, P. M., Yu. F., Qiu, L., Parsons, P. G. and Hayward N. K. (1995) "Evidence f o r UV induction o f CDKN2 mutations i n me1 anoma c e l l 1 i nes" Oncogene 11 : 663 - 668

17. Drobetsky, E. A., Turcotte, J. and Chateauneuf. A. (1995) "A r o l e f o r u l t r a v i o l e t A i n solar mutagenesis" Proc. N a t l . Acad. Sci . USA 92:2350-2354

18. Ohta. M., Nagai, H.. Shimizu, M., Rasio. D., Berd, D.. Mastrangelo. M., Singh, A. D.. Shields, J. A., Shields, C. L.. Croce, C. M. and Huebner, K. (1994) "Rarity o f somatic and germline mutations i n the cyclin-dependent kinase 4 i nhi b i t o r gene, CDK41, i n me1 anoma" Cancer Res. 54: 5269 - 5272

19. Vink. A. A.. Yarosh, D. B. and Kripke. M. L. (1996) "Chromophore f o r UV-induced immunosuppression: DNA" Photochem. Photobiol . 63:383-386

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