Volume 10 Supplement 2

Breast Cancer Research 2008

Open Access

Overexpression of CD44 in acquired tamoxifen-resistant breast cancer cells augments their migratory response to heregulin beta 1

  • S Hiscox1,
  • L Goddard1,
  • N Jordan1,
  • C Smith1,
  • M Harper1,
  • RI Nicholson1 and
  • J Gee1
Breast Cancer Research200810(Suppl 2):P34

https://doi.org/10.1186/bcr1918

Published: 13 May 2008

Background

Acquired endocrine resistance in breast cancer cells is accompanied by altered growth factor receptor signalling [1] and a highly migratory cell phenotype [2]. Interestingly, in tamoxifen-resistant (TamR) MCF7 cells, our microarray analysis has demonstrated elevated levels of CD44, a transmembrane glycoprotein known to interact with, and modulate the function of, growth factor receptors [3]. Here we have explored the role of CD44 as a modulator of heregulin beta-1-induced migratory signalling in TamR cells.

Methods

Expression of CD44 (standard and v3 isoforms) were confirmed by RT-PCR and western blotting and their association with erbB family members determined by both immunofluorescence microscopy and immunoprecipitation. Activation of intracellular signalling following heregulin beta 1 treatment (10 ng/ml) in the presence or absence of CD44 (using siRNA-mediated inhibition) was determined by western blotting using phosphospecific antibodies. Cellular migration was determined by seeding cells (control and CD44 siRNA-treated) into fibronectin-coated transwell chambers (8.0 μm pore size) in the presence or absence of heregulin beta 1. After 24 hours, migratory cells were fixed, stained with crystal violet and counted.

Results

Both standard and v3 isoforms of CD44 were overexpressed in TamR cells at both gene and protein levels (mean fold increase in CD44s protein (TamR versus MCF7): 4.26 ± 1.2, P < 0.05). Moreover, CD44s and v3 colocalised with Her2 and Her3 receptors at the cell surface and were also detectable in Her2/Her3 cellular immunoprecipitates. Treatment of TamR cells with heregulin resulted in phosphorylation of erbB receptors together with a number of downstream signalling intermediates, including Akt, Src and FAK, and resulted in enhanced cellular migration. Significantly, heregulin-induced intracellular signalling was dramatically reduced in cells in which the expression of CD44 was suppressed (via siRNA), with a corresponding loss of heregulin-induced migratory behaviour (mean fold change in cell migration versus untreated control: 6.7 ± 1.1, P < 0.05 (heregulin beta 1); 1.8 ± 0.9 (CD44 siRNA); 1.47 ± 0.6, P < 0.05 (heregulin beta 1 + CD44 siRNA)).

Conclusion

These data demonstrate a role for CD44 as a modulator of erbB receptor function in endocrine-resistant breast cancer cells, where it augments heregulin beta 1 migratory signalling.

Declarations

Acknowledgements

The authors acknowledge the support of Breast Cancer Campaign and the Tenovus charity in these studies

Authors’ Affiliations

(1)
Tenovus Centre for Cancer Research, Welsh School of Pharmacy, Cardiff University

References

  1. Jones HE, Gee JM, Hutcheson IR, Knowlden JM, Barrow D, Nicholson RI: Growth factor receptor interplay and resistance in cancer. Endocr Relat Cancer. 13: 45-51. 10.1677/erc.1.01275.Google Scholar
  2. Hiscox S, Morgan L, Green TP, Barrow D, Gee J, Nicholson RI: Elevated Src activity promotes cellular invasion and motility in tamoxifen resistant breast cancer cells. Breast Cancer Res Treat. 2006, 97: 263-274. 10.1007/s10549-005-9120-9.View ArticlePubMedGoogle Scholar
  3. Bertotti A, Comoglio PM: Tyrosine kinase signal specificity: lessons from the HGF receptor. Trends Biochem Sci. 2003, 28: 527-533. 10.1016/j.tibs.2003.09.001.View ArticlePubMedGoogle Scholar

Copyright

© BioMed Central Ltd 2008

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