Molecular Basis and Clinical Application of Growth-Factor-Independent In Vitro Myeloid Colony Formation in Chronic Myelomonocytic Leukemia.

Klaus Geissler,Temeida Graf,Rajko Kusec,Thomas Nösslinger,Agnes Barna,Gregor Hörmann,Eva Jäger,Armin Zebisch,Sigrid Machherndl-Spandl,Reinhard Stauder,Michael Gurbisz,Leopold Öhler,Michael Pfeilstöcker,Elmir Graf,Heinz Sill,Peter Valent

doi:10.3390/ijms21176057

Abstract

We have originally reported that colony-forming units granulocyte/macrophage (CFU-GM) formation is an in vitro feature of chronic myelomonocytic leukemia (CMML) and a strong predictor for short survival. Elucidation of the molecular basis underlying this in vitro phenomenon could be helpful to define molecular features that predict inferior outcome in patients. We studied the correlation between the mutational landscape and spontaneous colony formation in 164 samples from 125 CMML patients. As compared to wildtype samples, spontaneous in vitro CFU-GM formation was significantly increased in samples containing mutations in NRAS, CBL and EZH2 that were confirmed as independent stimulatory factors by multiple regression analysis. Inducible expression of mutated RAS but not JAK2 was able to induce growth factor independence of Ba/F3 cells. Whereas high colony CFU-GM growth was a strong unfavorable parameter for survival (p < 0.00001) and time to transformation (p = 0.01390), no single mutated gene had the power to significantly predict for both outcome parameters. A composite molecular parameter including NRAS/CBL/EZH2, however, was predictive for inferior survival (p = 0.00059) as well as for increased risk of transformation (p = 0.01429). In conclusion, we show that the composite molecular profile NRAS/CBL/EZH2 derived from its impact on spontaneous in vitro myeloid colony formation improves the predictive power over single molecular parameters in patients with CMML.

Highlights

Growth-factor-independent growth has been long considered as a hallmark of advanced malignancy [1]
We have originally shown that extensive formation of colony-forming units granulocyte/macrophage (CFU-GM) without the addition of exogenous growth factors is an in vitro characteristic of a subgroup of patients with chronic myelomonocytic leukemia (CMML) [4]
In 2004, we reported in a small retrospective study of 30 CMML patients that high spontaneous CFU-GM growth (≥100/105MNC) could be found in a subset of these patients who had a much worse prognosis than patients with low colony growth [7]

Summary

Introduction

Growth-factor-independent growth has been long considered as a hallmark of advanced malignancy [1]. We have originally shown that extensive formation of colony-forming units granulocyte/macrophage (CFU-GM) without the addition of exogenous growth factors is an in vitro characteristic of a subgroup of patients with CMML [4]. This observation has been reproduced by others [5,6] and seems to be an in vitro phenomenon, which is typical for CMML since it can be regularly demonstrated in CMML but is not a common finding in other MPNs including CML. These findings suggest that high spontaneous CFU-GM formation may be a functional surrogate of RAS-pathway hyperactivation, a detailed analysis of the molecular basis for growth-factor-independent myeloid colony formation is lacking

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