Regulation of Cytoskeleton Organization by Sphingosine in a Mouse Cell Model of Progressive Ovarian Cancer

Abstract

Ovarian cancer is a multigenic disease and molecular events driving ovarian cancer progression are not well established. We have previously reported the dysregulation of the cytoskeleton during ovarian cancer progression in a syngeneic mouse cell model for progressive ovarian cancer. In the present studies, we investigated if the cytoskeleton organization is a potential target for chemopreventive treatment with the bioactive sphingolipid metabolite sphingosine. Long-term treatment with non-toxic concentrations of sphingosine but not other sphingolipid metabolites led to a partial reversal of a cytoskeleton architecture commonly associated with aggressive cancer phenotypes towards an organization reminiscent of non-malignant cell phenotypes. This was evident by increased F-actin polymerization and organization, a reduced focal adhesion kinase expression, increased α-actinin and vinculin levels which together led to the assembly of more mature focal adhesions. Downstream focal adhesion signaling, the suppression of myosin light chain kinase expression and hypophosphorylation of its targets were observed after treatment with sphingosine. These results suggest that sphingosine modulate the assembly of actin stress fibers via regulation of focal adhesions and myosin light chain kinase. The impact of these events on suppression of ovarian cancer by exogenous sphingosine and their potential as molecular markers for treatment efficacy warrants further investigation.

Bioactive sphingolipid metabolites modulate ovarian cancer cell structural mechanics

“…23-24 The disruption of the intact actin cytoskeleton in MOSE-E or stabilization in MOSE-L significantly reversed the cells' elastic modulus, 22b highlighting the importance of the actin cytoskeleton for the biomechanical responses. However, treatment with So improved the actin organization and increased the f-actin levels which was associated with a decrease in invasive capacity; 39 this correlates well with the increase in elastic modulus determined in this study. Conversely, the sphingolipid metabolites associated with supporting cancer growth (S1P) and tumor-promoting inflammation (Cer) decreased the elastic modulus of MOSE cells and made the cells softer; neither Cer nor S1P induced actin stress fiber formation in MOSE-L cells.…”

“…Conversely, the sphingolipid metabolites associated with supporting cancer growth (S1P) and tumor-promoting inflammation (Cer) decreased the elastic modulus of MOSE cells and made the cells softer; neither Cer nor S1P induced actin stress fiber formation in MOSE-L cells. 39 This is in contrast to the effect in endothelial cells where S1P increases barrier function and peripheral stress fiber organization. 40 The latter may be dependent upon the differentiation and activation status of cells; MOSE-L cells represent a poorly differentiated cell that has clearly undergone an epithelial-to-mesenchymal transition (EMT) phase.…”

Ovarian tumor-initiating cells display a flexible metabolism

“…qPCR was performed using 50ng of cDNA with SensiMix Plus SYBR Mastermix (Quantace) in the ABI 7900HT (Applied Biosystems) with the following parameters: 42 cycles at 95°C for 10 minutes, 95°C for 15 seconds, 58°C for 30 seconds and 72°C for 15 seconds, followed by a dissociation curve segment. Data was quantified using the ΔΔCT method and expressed relative to RPL19 as the housekeeping gene as described previously[15, 17]. Data are expressed as mean ± SEM from three biological replicates performed in duplicate.…”

“…We have recently demonstrated that mouse ovarian surface epithelial (MOSE) cells, representing early (benign), intermediate, and late (aggressive and invasive) stages of ovarian cancer[14, 15] also exhibit an increasingly glycolytic phenotype[16]. As cells progress through distinct stages of the disease, they change their morphology and organization and increase their growth rate while acquiring the ability to grow as spheroids, invade collagen and form tumors in vivo [14, 15, 17]. By in vivo passaging, the late stage MOSE cells (MOSE-L) were enriched for tumor initiating cells - MOSE-L FFLv (hereafter referred to as TICs)-that exhibit increased tumorigenicity[18].…”

Comprehensive analysis of mRNA‐level and miRNA‐level subpathway activities for identifying robust ovarian cancer prognostic signatures

“…For path: 00380_5 (Tryptophan, top 1 in mRNA protective results), it was observed that patients with OvCa have increased tryptophan degradation compared to controls resulting in higher serum kynurenine concentrations, and elevated Kyn/Trp levels were shown to be associated with OvCa poor response to therapy and worse outcome . For path: 04810_3 (Regulation of actin cytoskeleton, top 6), study had reported the dysregulation of the cytoskeleton during OvCa progression in a mouse model . Moreover, the abnormal expression of Beta‐actin (ACTB) and the resulting changes to the cytoskeleton were associated with tumour invasiveness and metastasis .…”