Losses of FHIT and p16 in oral carcinogenesis –

a FISH based studyJohannes Bier

background – „leukoplakia“ 1/2

• oral leukoplakia main epithelial lesion of the mucosa of the mouth (prevalence: 2.3%)

• heterogeneous group with varying risk• premalignant epithelial precursor lesion of OSCC (3-8%

transform into cancer)• whitish patches• several grades: hyperplasia, low/high grade dysplasia,

CIS, invasive cancer• mainly due to carcinogens, i.e. nicotine, alcohol, but also

idiopathic

background – „leukoplakia“ 2/2

• no standardized regime for treatment• follow-up with biopsy and histopathology currently gold

standard • molecular biological techniques to be future proposals ?• no specific markers to predict malignant transformation

yet• LOH and polyploidy ?

so what?

there are hints...

• molecular progression model for oral carcinogenesis: accumulation of genetic changes (Califano et al.,1996) (adopted from Fearon & Vogelstein 1990: colon cancer)

• studies on LOH proposed 3p and 9p to be important for progression (Rosin et al., 2000; Mao et al.,1996)

• greater probability of progression into OSCC

3p and 9p...

• 3p14 alias FHIT (fragile histidine triade), 9p21 alias p16

• both tumor suppressor genes

• considered to indicate transition from hyperplasia to dysplasia

FISH what?!leukoplakia with hyperplasia – probes for FHITcentromeregene

FISH what?!

invasive carcinoma – probes for FHITcentromer

gene

results - deletion FHIT / p16

control (infant)

control (adult)

hyperplasia dysplasia cis OSCC normal epithelium of OSCC patients

0

25

50

75

100

perc

enta

ge o

f cel

ls w

ith d

elet

ion

3p (F

HIT)

115

919

control (infant)

control (adult)

hyperplasia dysplasia cis OSCC normal epithelium of OSCC patients

0

25

50

75

100

perc

enta

ge o

f cel

ls w

ith d

elet

ion

9p (p

16)

20

results - polysomy FHIT / p16

control (infants)

control (adults)

hyperplasia dysplasia cis OSCC normal epithelium of OSCC patients

0

25

50

75

100

per

cen

tag

e o

f ce

lls w

ith

po

lyso

my

9p (

p16

)64

68

6

33

88

18

13

56

27

10

55

control (infant)

control (adult)

hyperplasia dysplasia cis OSCC normal epithelium of OSCC patients

0

25

50

75

100

per

cen

tag

e o

f ce

lls w

ith

po

lyso

my

3p (

FH

IT)

62

6433

70

94

63

6

30

discussion

• already >90% of hyperplasia deletion for FHIT Califano et al. = 20%

• our threshold: 25% / 13% LOH studies 50%• FHIT earlier event than p16; results underline role of

FHIT regarding cell cycle regulation• possibility to distinguish deletion – amplification• hyperplasia does not show polysomy 3p or 9p• polysomy 3 indicator of increasing oral carcinogenesis