Epithelial-to-mesenchymal transition in FHC-silenced cells: the role of CXCR4/CXCL12 axis

Background

Ferritin plays a central role in the intracellular iron metabolism; the molecule is a nanocage of 24 subunits of the heavy and light types. The heavy subunit (FHC) is provided of a ferroxidase activity and thus performs the key transformation of iron in a non-toxic form. Recently, it has been shown that FHC is also involved in additional not iron-related critical pathways including, among the others, p53 regulation, modulation of oncomiRNAs expression and chemokine signalling. Epithelial to mesenchymal transition (EMT) is a cellular mechanism by which the cell acquires a fibroblast-like phenotype along with a decreased adhesion and augmented motility. In this work we have focused our attention on the role of the FHC on EMT induction in the human cell lines MCF-7 and H460 to elucidate the underlying molecular mechanisms.

Methods

Targeted silencing of the FHC was performed by lentiviral-driven shRNA strategy. Reconstitution of the FHC gene product was obtained by full length FHC cDNA transfection with Lipofectamine 2000. MTT and cell count assays were used to evaluate cell viability and proliferation; cell migration capability was assayed by the wound-healing assay and transwell strategy. Quantification of the CXCR4 surface expression was performed by flow cytometry.

Results

Experimental data indicated that FHC-silenced MCF-7 and H460 cells (MCF-7^shFHC, H460^shFHC) acquire a mesenchymal phenotype, accompanied by a significant enhancement of their migratory and proliferative capacity. This shift is coupled to an increase in ROS production and by an activation of the CXCR4/CXCL12 signalling pathway. We present experimental data indicating that the cytosolic increase in ROS levels is responsible for the enhanced proliferation of FHC-silenced cells, while the higher migration rate is attributable to a dysregulation of the CXCR4/CXCL12 axis.

Conclusions

Our findings indicate that induction of EMT, increased migration and survival depend, in MCF-7 and H460 cells, on the release of FHC control on two pathways, namely the iron/ROS metabolism and CXCR4/CXCL12 axis. Besides constituting a further confirmation of the multifunctional nature of FHC, this data also suggest that the analysis of FHC amount/function might be an important additional tool to predict tumor aggressiveness.

CXCR4 and CXCR7 transduce through mTOR in human renal cancer cells

Treatment of metastatic renal cell carcinoma (mRCC) has improved significantly with the advent of agents targeting the mTOR pathway, such as temsirolimus and everolimus. However, their efficacy is thought to be limited by feedback loops and crosstalk with other pathways leading to the development of drug resistance. As CXCR4-CXCL12-CXCR7 axis has been described to have a crucial role in renal cancer; the crosstalk between the mTOR pathway and the CXCR4-CXCL12-CXCR7 chemokine receptor axis has been investigated in human renal cancer cells. In SN12C and A498, the common CXCR4-CXCR7 ligand, CXCL12, and the exclusive CXCR7 ligand, CXCL11, activated mTOR through P70S6K and 4EBP1 targets. The mTOR activation was specifically inhibited by CXCR4 antagonists (AMD3100, anti-CXCR4-12G5 and Peptide R, a newly developed CXCR4 antagonist) and CXCR7 antagonists (anti-CXCR7-12G8 and CCX771, CXCR7 inhibitor). To investigate the functional role of CXCR4, CXCR7 and mTOR in human renal cancer cells, both migration and wound healing were evaluated. SN12C and A498 cells migrated toward CXCL12 and CXCL11; CXCR4 and CXCR7 inhibitors impaired migration and treatment with mTOR inhibitor, RAD001, further inhibited it. Moreover, CXCL12 and CXCL11 induced wound healing while was impaired by AMD3100, the anti CXCR7 and RAD001. In SN12C and A498 cells, CXCL12 and CXCL11 promoted actin reorganization characterized by thin spikes at the cell periphery, whereas AMD3100 and anti-CXCR7 impaired CXCL12/CXCL11-induced actin polymerization, and RAD001 treatment further reduced it. In addition, when cell growth was evaluated in the presence of CXCL12, CXCL11 and mTOR inhibitors, an additive effect was demonstrated with the CXCR4, CXCR7 antagonists and RAD001. RAD001-resistant SN12C and A498 cells recovered RAD001 sensitivity in the presence of CXCR4 and CXCR7 antagonists. In conclusion, the entire axis CXCR4-CXCL12-CXCR7 regulates mTOR signaling in renal cancer cells offering new therapeutic opportunities and targets to overcome resistance to mTOR inhibitors.

CXCR4 in melanoma: A prognostic biomarker and a target of therapy

8051

Background: The chemokine receptor CXCR4 was identified as an independent predictor of poor prognosis in primary melanoma. In melanoma metastases CXCR4 is also expressed and functional suggesting that CXCR4 has a role in the melanoma biology. Differential chemokine receptors expression by activated tumor specific CD8+ T cells can be associated with divergent clinical outcomes. Expression of CXCR3 by CD8+ T cells was reported to be associated with survival in melanoma patients with stage III disease. To further characterize the role of CXCR4 in the melanoma metastatization we analyzed Fine Needle Ago Biopsy (FNAB) from disease involved lymph nodes. Moreover, we are currently evaluating CD8+ subpopulation for the expression of CXCR4 during the follow up Methods: FNAB of suspicious disease involved lymphnodes. was performed and the cell suspension was analyzed by flow cytometry and .immunocytochemistry. Peripheral blood lymphocytes (PBL) was analyzed by flow cytometry Results: FNAB were performed on 25. suspicious lymphnodes. Out of 25 FNAB 19 were positive per melanoma cells (HMB45 positive). Concomitant expression of HMB45 and CXCR4 was detected in 15 out of 19 samples.with the percentage of cells CXCR4 positive being the large majority ( 40–100%) of the detected melanoma cells. Ongoing studies are further characterizing the biology of the CXCR4/HMB45 cells. The inhibition of this cells migrating through the lymphnode may interfere with the metastatization. In relation to the CD8+ subpopulation for the expression of CXCR4 during the follow up preliminary data at the time of diagnosis showed a correlation between the activated CD8 + lymphocytes (HLA-DR+) /CXCR4 + and the level of invasion of the lesion. Conclusion: Altoghether these evidences confirm a role of CXCR4 in melanoma biology and as therapeuthic target .

No significant financial relationships to disclose.