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Extracellular calcium regulates keratinocyte proliferation and HPV 16 E6 RNA expression in vitro
Author(s) -
Turunen Aaro,
Syrjänen Stina
Publication year - 2014
Publication title -
apmis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.909
H-Index - 88
eISSN - 1600-0463
pISSN - 0903-4641
DOI - 10.1111/apm.12227
Subject(s) - involucrin , keratinocyte , extracellular , calcium , microbiology and biotechnology , cell growth , cell culture , biology , downregulation and upregulation , oncogene , in vitro , proliferation marker , cell , chemistry , biochemistry , cell cycle , genetics , organic chemistry , gene
Human papillomaviruses ( HPV ) are known to immortalize oral keratinocytes in vitro, but the underlying mechanisms causing the following resistance to differentiation remain unclear. We investigated the effect of extracellular calcium on the proliferation of HPV 16‐positive keratinocytes and on the mRNA expression of the viral E6‐oncogene. HPV 16‐positive hypopharyngeal carcinoma cells ( UD ‐ SCC ‐2), spontaneously immortalized‐ ( HMK ) and HPV 16 E6/E7‐immortalized human gingival keratinocytes ( IHGK ) were grown for 3, 6 and 9 days in Keratinocyte Serum‐free Medium with calcium concentrations ranging from 0 mM to 6 mM. Calcium concentrations up to 0.09 mM increased cellular proliferation, which decreased at higher concentrations. A shift of calcium concentration from 0 to 4 mM increased E6 expression in UD ‐ SCC ‐2 cells 2.4‐fold by day 9. Simultaneously, E2 expression increased. The most significant upregulation of E6 and E2 expressions was observed at day 9, grown in high‐calcium media and the increase in E6 expression coincided with an increase in involucrin expression, likely indicating cell differentiation. Despite this, HPV ‐positive cells continued to proliferate even at high‐calcium media in contrast to HPV ‐negative cells. Overexpression of E6 mRNA may be an important feature of HPV16‐positive cells to resist the natural calcium gradient in differentiating keratinocytes allowing cell proliferation.