Blood and skin-derived Sezary cells: differences in proliferation-index, activation of PI3K/AKT/mTORC1 pathway and its prognostic relevance

Abstract

Sézary syndrome (SS) is a rare and aggressive variant of Cutaneous T-Cell Lymphoma characterized by neoplastic distribution mainly involving blood, skin, and lymph-node. Although a role of the skin microenvironment in SS pathogenesis has long been hypothesized, its function in vivo is poorly characterized. To deepen this aspect, here we compared skin to blood-derived SS cells concurrently obtained from SS patients highlighting a greater proliferation-index and a PI3K/AKT/mTORC1 pathway activation level, particularly of mTOR protein, in skin-derived-SS cells. We proved that SDF-1 and CCL21 chemokines, both overexpressed in SS tissues, induce mTORC1 signaling activation, cell proliferation and Ki67 up-regulation in a SS-derived cell line and primary-SS cells. In a cohort of 43 SS cases, we observed recurrent copy number variations (CNV) of members belonging to this cascade, namely: loss of LKB1 (48%), PTEN (39%) and PDCD4 (35%) and gains of P70S6K (30%). These alterations represent druggable targets unraveling new therapeutic treatments as metformin here evaluated in vitro. Moreover, CNV of PTEN, PDCD4, and P70S6K, evaluated individually or in combination, are associated with reduced survival of SS patients. These data shed light on effects in vivo of skin-SS cells interaction underlying the prognostic and therapeutic relevance of mTORC1 pathway in SS.

Preclinical Evidence for Targeting PI3K/mTOR Signaling with Dual-Inhibitors as a Therapeutic Strategy against Cutaneous T-Cell Lymphoma

“…We previously described the copy number (CN) variation of the PTEN gene and the members of the TORC1 pathway in SS patients (Cristofoletti et al, 2019b(Cristofoletti et al, , 2013. In this study, we performed the CN variation analysis by droplet digital PCR (ddPCR) in six new enrolled patients.…”

“…The mammalian target of rapamycin (mTOR) pathway is affected in SS by several means. Key components of mTOR pathway are altered at the genomic level by chromosomal deletion or amplification, such as loss of LKB1 (48%), PTEN (39%), PDCD4 (35%), and gain of P70S6K (30%) (Cristofoletti et al, 2019b(Cristofoletti et al, , 2013da Silva Almeida et al, 2015). PTEN expression is also reduced by microRNAs, indicating other regulatory mechanisms (Cristofoletti et al, 2013;Song et al, 2012).…”

“…PTEN expression is also reduced by microRNAs, indicating other regulatory mechanisms (Cristofoletti et al, 2013;Song et al, 2012). Phosphorylation of the phosphoinositide 3-kinases(PI3K)/protein kinase B (AKT)/mTOR cascade is hyperactivated in SS cells by microenvironmental signals such as chemokines and cytokines (Cristofoletti et al, 2019b;Marzec et al, 2008). In particular, malignant lymphocytes in the skin tumor niche, are highly stimulated by the chemokine SDF-1 (Narducci et al, 2006), which induces proliferation and activates the mTOR pathway (Cristofoletti et al, 2019b;Munk et al, 2011).…”

“…Phosphorylation of the phosphoinositide 3-kinases(PI3K)/protein kinase B (AKT)/mTOR cascade is hyperactivated in SS cells by microenvironmental signals such as chemokines and cytokines (Cristofoletti et al, 2019b;Marzec et al, 2008). In particular, malignant lymphocytes in the skin tumor niche, are highly stimulated by the chemokine SDF-1 (Narducci et al, 2006), which induces proliferation and activates the mTOR pathway (Cristofoletti et al, 2019b;Munk et al, 2011). In addition, mTOR inhibitors have been investigated in CTCL by in vitro experiments, xenograft mouse models, and in a pilot phase II trial (Gupta et al, 2012;Kittipongdaja et al, 2015;Kremer et al, 2010;Marzec et al, 2008;Witzig et al, 2015), suggesting a potential therapeutic activity (Dienstmann et al, 2014).…”

Extracorporeal Photopheresis: A Case of Immunotherapy Ahead of Its Time

“…Additionally, p21 is a potent suppressor of the PI3K pathway during cell cycle arrest [37]. In fact, hitting PI3K may be a prominent factor in the therapeutic effect of ECP as the PI3K pathway is often involved in oncogenesis of CTCL patients and the severity of GvHD in animal models [38, 39]. 8-MOP/UVA exposure decreases the decoding of signal transduction by inducing changes in the cell membrane as a consequence of 8-MOP intercalation and covalent binding to phospholipids [40].…”