Down regulation of the expression of the p110, p85 and p55 subunits of phosphatidylinositol 3-kinase during colon cancer cell anchorage-independent growth

Laura C. Yeates, Alfred Gallegos, Alan P. Kozikowski, Garth Powis

Research output: Contribution to journalArticle

Abstract

We have found that analogues of phosphatidylinositol modified at the 3'-myo-inositol position prevent phosphorylation by phosphatidylinositol 3-kinase (PI3-kinase) inhibit the anchorage-independent growth of HT-29 human colon adenocarcinoma cells as colonies in soft agarose but have no effect on monolayer growth on a plastic surface. Examination of an incomplete differential display library revealed 3 genes whose expression was increased and 11 genes whose expression was decreased or absent in HT-29 cells growing as colonies compared to monolayer growth. One of the cDNAs corresponding to an mRNA that was expressed only in cells growing as a monolayer was a 126 bp fragment that had 98% identity with a fragment of mRNA for human p55(PIK) PI3-kinase regulatory subunit. The down regulation of p55(PIK) gene expression in HT-29 cells growing as colonies was confirmed by RT-PCR using p55(PIK)-specific oligonucleotide primers. RT-PCR and Northern hybridisation were used to show that the expression of the p110 catalytic subunit and the p85 regulatory subunit of PI3-kinase were also down regulated in HT-29 cells growing as colonies. We measured a decrease of approximately 25% in total PI3-kinase activity of the HT-29 cells grown in soft agarose compared to HT-29 cells grown as monolayers. The results suggest that p110 PI3-kinase activity may be limiting in cells showing anchorage independent-growth which could explain their increased sensitivity, compared to cells in monolayer culture, to inhibitors of PI3-kinase signalling.

Original languageEnglish (US)
Pages (from-to)4171-4176
Number of pages6
JournalAnticancer research
Volume19
Issue number5 B
StatePublished - 1999

Keywords

  • 3'-Modified-phosphatidylinositols
  • Anchorage-independence
  • Differential display
  • Phosphatidylinositol 3-kinase
  • p55(PIK)

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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