Publication in detail

The Journal of clinical investigation 2012 Feb 1;122(2):553-7. doi: 10.1172/JCI59309. Epub 2012 Jan 3.

An activating Pik3ca mutation coupled with Pten loss is sufficient to initiate ovarian tumorigenesis in mice.

Kinross, KM; Montgomery, KG; Kleinschmidt, M; Waring, P; Ivetac, I; Tikoo, A; Saad, M; Hare, L; Roh, V; Mantamadiotis, T; Sheppard, KE; Ryland, GL; Campbell, IG; Gorringe, KL; Christensen, JG; Cullinane, C; Hicks, RJ; Pearson, RB; Johnstone, RW; McArthur, GA; Phillips, WA

Cancer Research Division, Peter MacCallum Cancer Centre (Peter Mac), East Melbourne, Victoria, Australia.

Abstract:
Injection of antigens coupled to antibodies against the dendritic cell (DC) surface molecule Clec9A has been shown to produce strongly enhanced antibody responses even without co-administration of adjuvants, via antigen presentation by DC on MHC class II and consequent production of follicular helper T cells. A series of mutant mice were tested to determine the DC subtypes responsible for this MHC II presentation of targeted antigen, compared to presentation of antigen on MHC I. A new clec9A null mouse was developed; these mice did not give enhanced antibody production, confirming the response was dependent on Clec9A-expressing DC. However targeting of antigen to Clec9A in batf3 null mice produced enhanced antibody responses despite the marked reduction in CD8(+) DC, the major Clec9A-expressing DC subtype. This was shown to be dependent on efficient MHC II presentation by minor Clec9A-expressing DC subtypes in the environment of the Batf3(-/-) mice, namely early cells of the CD8 DC lineage and the plasmacytoid-related CD8(+) DC subset, but not by plasmacytoid cells themselves. However in normal mice most MHC II presentation of the Clec9A-targeted antigen was by the major CD8(+) DC population, the DC also responsible for presentation on MHC I.Mutations in the gene encoding the p110α subunit of PI3K (PIK3CA) that result in enhanced PI3K activity are frequently observed in human cancers. To better understand the role of mutant PIK3CA in the initiation or progression of tumorigenesis, we generated mice in which a PIK3CA mutation commonly detected in human cancers (the H1047R mutation) could be conditionally knocked into the endogenous Pik3ca locus. Activation of this mutation in the mouse ovary revealed that alone, Pik3caH1047R induced premalignant hyperplasia of the ovarian surface epithelium but no tumors. Concomitantly, we analyzed several human ovarian cancers and found PIK3CA mutations coexistent with KRAS and/or PTEN mutations, raising the possibility that a secondary defect in a co-regulator of PI3K activity may be required for mutant PIK3CA to promote transformation. Consistent with this notion, we found that Pik3caH1047R mutation plus Pten deletion in the mouse ovary led to the development of ovarian serous adenocarcinomas and granulosa cell tumors. Both mutational events were required for early, robust Akt activation. Pharmacological inhibition of PI3K/mTOR in these mice delayed tumor growth and prolonged survival. These results demonstrate that the Pik3caH1047R mutation with loss of Pten is enough to promote ovarian cell transformation and that we have developed a model system for studying possible therapies.

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