# Presentation: 410947

## ECTOPIC EXPRESSION OF THE GLYCOPROTEIN HORMONE -SUBUNIT IN LUNG CANCER 

- Virginia D. Sarapura, MD
- Division of EndocrinologyUniversity of Colorado Health Siences Center

## Acknowledgements

- Danielle J. Haakinson
- Suzy R. Lewis
- William M. Wood
- David F. Gordon
- E. Chester Ridgway
- Wilbur Franklin
- Chris Coulter

## Glycoprotein hormone -Subunit

- Pituitary:
- Gonadotropes:  LH,FSH
- Thyrotropes: TSH
- Placenta: CG

- Solid tumors:
- Pancreas
- Lung
- Colon

- Dimerof & specific 

- free -subunit

- free -subunit

- Eutopic

- Ectopic

## Normal Function of Free -Subunit?

- Studies in 80’s: -subunit “purified” from pit- contaminated ???
- Pituitary: lactotrope differentiation (Chabot 2001)
- Placenta: prolactin production (Blithe 1998)
- Testes: testosterone production (Erickson 1990)
- Prostate: inhibition of stromal cell differentiation 	to smooth muscle cells (Rumpold 2002)

## Function of Free -Subunit in Tumors

- Cervical cancer: HeLa cell growth (Cox 1997)
- Lung cancer: ChaGo cell growth (Biswas 1992)
- Prostate cancer: correlates w/ ER (Bieche 2002)
- Breast cancer: correlates w/ ER    & responsiveness to treatment (Bieche 2001)

- Free -subunit receptor not identified yet

## Lung Cancer

- Significant prevalence & mortality
- free -subunit is expressed in ~1/3 of both SCLC (20%) & NSCLC (80%)
- Cell lines available for studies: ChaGo

- Control

- Antisense  RNA

- Control

- Antisense  RNA

- Rivera 1989,108:2423

## Ectopic -Subunit in ChaGo

- Butyrate but not cAMP stimulates -subunit expression in ChaGo– opposite to placenta (Weintraub 1985, Darnell 1985)
- Cycloheximide inhibits a putative -subunit p50 repressor in ChaGo (Cox 1990)

## Mechanism of -Subunit ExpressionPituitary vs Placenta

- Sequences beyond -200 bp upstream
- (Nilson, Jameson, Mellon, Maurer, Camper, Ridgway)

- Proximal 200 bp in the 5’ flanking region
- (Jameson, Nilson)

- -3700
- URA

- -337/-330
- PGBE

- -220/-200
- GSE

## -Subunit Expressionin ChaGo cells

- -3700
- URA

- -337/-330
- PGBE

- -220/-200
- GSE

- Northern blot analysis

- ?

- ?

- ?

- ?

- ?

## -Subunit Deletional Analysis

## -Subunit Mutational Analysis

- Between -360 and -244

## ChaGo Nuclear Proteins Interact with h-307/-270 Region

- SW: h-307/-270

- FP: h-357/-99

## Mut-284/-270 abrogates binding 

- SW:
- h-307/-270

- EMSA:
- h-307/-270

## Sequence Analysish-307/-257

- 50-60 kDa = p50
- ≠
- 30 kDa signal

- ?

## -Subunit Expression in Lung Cancer Samples

## Ets-1 Expression in Lung Cancer Samples

## Summary

- Ectopic -subunit expression in ChaGo lung cancer cells does not require elements important in eutopic sites, but appears to require the –307/–270 region.
- The –307/–270 region binds specifically to ChaGo nuclear proteins and contains sequences homologous to Ets-1 and PEA-3 consensus binding sites.
- Ets-1 expression appears to be inversely correlated with -subunit expression in lung cancer, and may be a repressive factor.

## Conclusion

- Ectopic -subunit expression in lung cancer, and probably also in other malignant tumors, occurs by unique mechanisms that appear to be different from those in eutopic sites.
- Elucidating this is important because -subunit may impact tumor growth and responsiveness to treatment.