A novel E2F/sphingosine kinase 1 axis regulates anthracycline response in squamous cell carcinoma

Hazar-Rethinam, Mehlika, Merida De Long, Lilia, Gannon, Orla M., Topkas, Eleni, Boros, Samuel, Vargas, Ana Cristina, Dzienis, Marcin, Mukhopadhyay, Pamela, Simpson, Fiona, Endo-Munoz, Liliana and Saunders, Nicholas A. (2015) A novel E2F/sphingosine kinase 1 axis regulates anthracycline response in squamous cell carcinoma. Clinical Cancer Research, 21 2: 417-427. doi:10.1158/1078-0432.CCR-14-1962

Author Hazar-Rethinam, Mehlika
Merida De Long, Lilia
Gannon, Orla M.
Topkas, Eleni
Boros, Samuel
Vargas, Ana Cristina
Dzienis, Marcin
Mukhopadhyay, Pamela
Simpson, Fiona
Endo-Munoz, Liliana
Saunders, Nicholas A.
Title A novel E2F/sphingosine kinase 1 axis regulates anthracycline response in squamous cell carcinoma
Journal name Clinical Cancer Research   Check publisher's open access policy
ISSN 1557-3265
Publication date 2015-01-15
Year available 2014
Sub-type Article (original research)
DOI 10.1158/1078-0432.CCR-14-1962
Open Access Status
Volume 21
Issue 2
Start page 417
End page 427
Total pages 11
Place of publication Philadelphia, PA, United States
Publisher American Association for Cancer Research
Collection year 2015
Language eng
Formatted abstract
Purpose: Head and neck squamous cell carcinomas (HNSCC) are frequently drug resistant and have a mortality rate of 45%. We have previously shown that E2F7 may contribute to drug resistance in SCC cells. However, the mechanism and pathways involved remain unknown.

Experimental Design: We used transcriptomic profiling to identify candidate pathways that may contribute to E2F7-dependent resistance to anthracyclines. We then manipulated the activity/expression of the candidate pathway using overexpression, knockdown, and pharmacological inhibitors in in vitro and in vivo models of SCC to demonstrate causality. In addition, we examined the expression of E2F7 and a downstream effector in a tissue microarray (TMA) generated from HNSCC patient samples.

Results: E2F7-deficient keratinocytes were selectively sensitive to doxorubicin and this was reversed by overexpressing E2F7. Transcriptomic profiling identified Sphingosine kinase 1 (Sphk1) as a potential mediator of E2F7-dependent drug resistance. Knockdown and overexpression studies revealed that Sphk1 was a downstream target of E2F7. TMA studies showed that E2F7 overexpression correlated with Sphk1 overexpression in human HNSCC. Moreover, inhibition of Sphk1 by shRNA or the Sphk1-specific inhibitor, SK1-I (BML-EI411), enhanced the sensitivity of SCC cells to doxorubicin in vitro and in vivo. Furthermore, E2F7-induced doxorubicin resistance was mediated via Sphk1-dependent activation of AKT in vitro and in vivo.

Conclusion: We identify a novel drugable pathway in which E2F7 directly increases the transcription and activity of the Sphk1/S1P axis resulting in activation of AKT and subsequent drug resistance. Collectively, this novel combinatorial therapy can potentially be trialed in humans using existing agents.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Available Online: 19 November 2014.

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2015 Collection
UQ Diamantina Institute Publications
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