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Clin Cancer Res. 2019 Aug 15;25(16):5122-5134. doi: 10.1158/1078-0432.CCR-19-0206. Epub 2019 May 21.

Arginine Starvation and Docetaxel Induce c-Myc-Driven hENT1 Surface Expression to Overcome Gemcitabine Resistance in ASS1-Negative Tumors.

Author information

1
Division of Medical Oncology, Washington University in St. Louis, St. Louis, Missouri.
2
Department of Surgery, Washington University School of Medicine, St. Louis, Missouri.
3
Alvin J. Siteman Cancer Center, Washington University School of Medicine, St. Louis, Missouri.
4
Division of Medical Oncology, Washington University in St. Louis, St. Louis, Missouri. bvantine@wustl.edu.

Abstract

PURPOSE:

The response to acute and long-term arginine starvation results in a conditional adaptive metabolic reprogramming that can be harnessed for therapeutic opportunities in ASS1-negative tumors. Here, we investigate the underlying biology of priming ASS1- tumors with arginine deiminase (ADI-PEG20) before treatment with gemcitabine (GEM) and docetaxel (DTX) in sarcoma, pancreatic cancer, and melanoma cell lines.

EXPERIMENTAL DESIGN:

ASS1- tumor cell lines were treated to create LTAT (long-term ADI treated) cell lines (ASS1+) and used for drug combination studies. Protein expression of ASS1, dCK, RRM2, E2F1, c-MYC, and hENT1 was measured. c-MYC activity was determined, live-cell immunofluorescent studies for hENT1, uptake assays of FITC-cytosine probe, and rescue studies with a c-MYC inhibitor were all determined in the presence or absence of the ADI-PEG20:GEM:DTX.

RESULTS:

In examining modulations within the pyrimidine pathway, we identified that the addition of DTX to cells treated with ADI-PEG20 resulted in translocation of stabilized c-Myc to the nucleus. This resulted in an increase of hENT1 cell-surface expression and rendered the cells susceptible to GEM. In vivo studies demonstrate that the combination of ADI-PEG20:GEM:DTX was optimal for tumor growth inhibition, providing the preclinical mechanism and justification for the ongoing clinical trial of ADI-PEG20, GEM, and DTX in sarcoma.

CONCLUSIONS:

The priming of tumors with ADI-PEG20 and DTX results in the stabilization of c-MYC potentiating the effect of GEM treatment via an increase in hENT1 expression. This finding is applicable to ASS1-deficient cancers that are currently treated with GEM.

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