A Comprehensive Immunohistochemical Approach of AKT/mTOR Pathway and p-STAT3 in Mycosis Fungoides.
Authors: Siakantaris Marina , Levidou Georgia , Papadaki Theodora , Papadavid Evangelia , Vassilakopoulos Theodoros P. , Angelopoulou Maria K. , Marinos Leonidas , Nikolaou Vassiliki , Economidi Aphrodite , Antoniou Christina , Patsouris Efstratios , Pangalis G.A. , Korkolopoulou Penelope 
Published: October 2019

Abstract
Abstract 2663

Background:
Given the recent identification of the mTOR pathway as a possible target for cancer therapy, the expression pattern of phosphorylated mTOR (p-mTOR) pathway components has attracted vivid scientific interest in several neoplasms, including primary cutaneous T cell lymphomas. However, published information examining crosstalk between AKT/mTOR cascade and interconnected signaling pathways in mycosis fungoides (MF) is limited.

Materials:
We analysed immunohistochemically 54 skin biopsies (21 tumour and 33 plaque stage) from 50 patients with MF, for whom clinical information was available. Paraffin embedded tissue was stained for p-mTOR, its upstream p-AKT, its downstream effectors p-p70S6K and p-4E-BP1, as well as for p-ERK1/2 (extracellular signal-related kinase 1/2), the transcription factor Notch-1 and a member of the mammalian family of signal transducer activator of transcription, namely p-STAT-3. For statistical analysis only the predominant pattern i.e. cytoplasmic for p-mTOR, p-AKT, and NOTCH1 and nuclear for p-STAT3, p-p70S6K, p-4E-BP1 and p-ERK1/2 was taken into account. A Histo-score (H-score) based on the percentage of stained neoplastic cells (labelling index-LI) multiplied by staining intensity for each protein was calculated and was correlated with clinicopathological features and cancer-free (CSS), disease-free (DFS) and progression-free (PFS) survival.

Results:
p-p70S6K expression was recorded in all cases, whereas the rate of positivity for the remaining molecules ranged from 52.8% to 67.3%. p-mTOR was coexpressed with p-p70S6K in 67.3% of cases, but coexpression with other molecules was less common (27.4–38.5%). Notch-1 displayed higher H-scores in tumours than in plaques (p=0.0475), as previously demonstrated. The same applied to p-p70S6K, but this correlation was of borderline significance. Significant correlations were recorded between p-4E-BP1 and p-p70S6K (p=0.0019), p-ERK and p4E-BP1 (p=0.0588), as well as between Notch-1 and p-p70S6K (p=0.0001) and p-4E-BP1 (p=0.0003). The latter two correlations remained when plaques and tumours were analysed separately. Interestingly, p-STAT3 showed a weak positive correlation with p-AKT in the entire cohort, but when analysis was restricted to plaques this relationship became statistically significant (p=0.0419). Notch1, p-4E-BP1 and p-p70S6K expression were associated with advanced stage. In univariate survival analysis increased p-p70S6K (p=0.0174) and p-AKT (p=0.0198) H-scores as well as p-4E-BP-1 immunopositivity adversely affected CSS but not DFS in plaques, along with CD30 expression (p=0.0004). In particular, blood clonality affected both DFS and CSS, as well as time to disease progression (p=0.0009, p=0.0031 and p=0.0216 respectively). The CSS time was also substantially shortened for subjects with simultaneous overexpression of p-AKT and p-p70S6K along with p-4E-BP1 immunopositivity (p= 0.0001). On the contrary in the subgroup of tumours decreased p-STAT3 H-score was only parameter that adversely affected CSS in tumour stage (p=0.0394), with the presence of blood clonality attaining marginal significance in this regard.

Conclusions:
Activation of AKT-mTOR components appears to have an intimate liaison with NOTCH1, p-ERK and p-STAT-3 and seems to be implicated in disease progression and in the acquisition of a more aggressive phenotype. Phosphorylation of several key components of this pathway, namely AKT, p70S6K and 4E-BP1 in MF, single or in combinations emerge as potential markers of prognostic value in plaque stage, whereas in tumours p-STAT-3 is brought forward as a favourable prognostic marker.

Disclosures:
No relevant conflicts of interest to declare.