Alterations of the p53 and PIK3CA/AKT/mTOR pathways in angiosarcomas: a pattern distinct from other sarcomas with complex genomics

Abstract

Background: The p53 and phosphoinositide-3-kinase, catalytic, alpha polypeptide/v-akt murine thymoma viral oncogene homolog/mechanistic target of rapamycin (PIK3CA/AKT/mTOR) pathways frequently are altered in sarcoma with complex genomics, such as leiomyosarcoma (LMS) or undifferentiated pleomorphic sarcoma (UPS). The scale of genetic abnormalities in these pathways remains unknown in angiosarcoma (AS).

Methods: The authors investigated the status of critical genes involved in the p53 and PIK3CA/AKT/mTOR pathways in a series of 62 AS.

Results: The mutation and deletion rates of tumor protein 53 (TP53) were 4% and 0%, respectively. Overexpression of p53 was detected by immunohistochemistry in 49% of patients and was associated with inferior disease-free survival. Although p14 inactivation or overexpression of the human murine double minute homolog (HDM2) were frequent in LMS and UPS and could substitute for TP53 mutation or deletion, such alterations were rare in angiosarcomas. Phosphorylated ribosomal protein S6 kinase (p-S6K) and/or phosphorylated eukaryotic translation initiation factor 4E binding protein 1 (p-4eBP1) overexpression was observed in 42% of patients, suggesting frequent activation of the PIK3CA/AKT/mTOR pathway in angiosarcomas. Activation was not related to intragenic deletion of phosphatase and tensin homolog (PTEN), an aberration that is frequent in LMS and UPS but absent in angiosarcomas.

Conclusions: The current results indicated that angiosarcomas constitute a distinct subgroup among sarcomas with complex genomics. Although TP53 mutation and PTEN deletion are frequent in LMS and UPS, these aberrations are rarely involved in the pathogenesis of angiosarcoma.

Figure 1

Immunohistochemical (IHC) results for p53 (A,B,C), p14 (D), HDM2 (E) and prognostic impact of p53 expression (F). (A,B) Diffuse and strong nuclear reactivity for p53 in a secondary AS associated with a TP53 mutation and KDR mutation (A: AS17, 200x) and a primary AS without TP53 mutation (B: AS59, 200x). (C) Absence of expression of p53 in a case of secondary AS (AS19, 200x). (D) Diffuse nuclear reactivity for p14 in a secondary AS (AS20, 200x). (E) Absence of expression of HDM2 in a case of secondary AS (AS39, 200x). (F) Kaplan Meier curve for disease-free survival according to p53 IHC status (blue line: negative; green line: positive).

Figure 2

Immunohistochemical (IHC) results for p-S6K (A), p-4eBP1 (B) and p44/p-ERK (C). Diffuse and strong reactivity for pS6K (A, 200x), p-4eBP1 (B, 200x) and p44/p-ERK (C, 200x) in a primary angiosarcoma (AS9).