Dysfunctional AMPK activity, signalling through mTOR and survival in response to energetic stress in LKB1-deficient lung cancer

LKB1, mutated in Peutz-Jeghers and in sporadic lung tumours, phosphorylates a group of protein kinases named AMP-activated protein kinase (AMPK)-related kinases. Among them is included the AMPK, a sensor of cellular energy status. To investigate the relevance of LKB1 in lung carcinogenesis, we study several lung cancer cells with and without LKB1-inactivating mutations. We report that LKB1-mutant cells are deficient for AMPK activity and refractory to mTOR inhibition upon glucose depletion but not growth-factor deprivation. The requirement for wild-type LKB1 to properly activate AMPK is further demonstrated in genetically modified cancer cells. In addition, LKB1-deficient lung primary tumours had diminished AMPK activity, assessed by complete absence or low level of phosphorylation of its critical substrate, acetyl-CoA carboxylase. We also demonstrate that LKB1 wild-type cells are more resistant to cell death upon glucose withdrawal than their mutant counterparts. Finally, modulation of AMPK activity did not affect PI3K/AKT signalling, an advantage for the potential use of AMPK as a target for cancer therapy in LKB1 wild-type tumours. Thus, sustained abrogation of cell energetic checkpoint control, through alterations at key genes, appear to be an obligatory step in the development of some lung tumours.

FOXP3, a selective marker for a subset of adult T-cell leukaemia/lymphoma

FOXP3 is a forkhead transcription factor family member, implicated in T-cell regulation, activation and differentiation. FOXP3 has been shown to be a master control gene for the development and function of CD4+/CD25+ regulatory T-cells (T(reg)). In this study, FOXP3 protein expression has been analysed using a new anti-FOXP3 monoclonal antibody in 172 paraffin-embedded lymphoma samples. FOXP3 expression in tumour cells was confined to adult T-cell leukaemia/lymphoma (ATLL) cases (17/25, 68%), with some variability in the intensity of the staining and the proportion of positive cells. No other lymphoma types studied exhibited FOXP3 expression in the malignant population. The selective expression of FOXP3 by tumour cells in ATLL makes this antibody a potentially useful diagnostic tool.

Simultaneous detection of the immunophenotypic markers and genetic aberrations on routinely processed paraffin sections of lymphoma samples by means of the FICTION technique

Disciplines such as morphology, immunophenotyping and genetics widely contributed over decades to the understanding of the cellular mechanisms of cancer. To obtain a greater insight into the complex processes of tumorigenesis, scientists have joined their efforts to combine many of the available techniques. Here, we report on the development of a FICTION (Fluorescence Immunophenotyping and Interphase Cytogenetics as a tool for the Investigation of Neoplasms) technique that allows a simultaneous detection of immunophenotypic markers and genetic aberrations on routinely processed lymphoma samples. As the antigen retrieval method seems to play an important role in the final results, we tested the pressure-cooking method at different times (2, 4 and 8 min) using three different buffers (EDTA, Tris-EDTA and citrate), resulting in improved sensitivity for the detection of both immunophenotypic markers and genetic aberrations. We also applied this method to different types of lymphoma using double immunofluorescence assays (including CD30, CD20, CD8 monoclonal antibodies) and several fluorescence in situ hybridization probes to demonstrate that the FICTION technique could be easily applied on paraffin sections in different combinations for the diagnosis and research of cancer.