Abstract
This work aimed to discover targets for combination treatment with gemcitabine in pancreatic cancer. We selected 11 tumors from our live collection of freshly generated pancreatic cancer xenografts with known degrees of varying gemcitabine sensitivity. We briefly (6 h) exposed fine-needle aspiration material to control vehicle or gemcitabine (1 mumol/L) and compared the gene expression of the treated and untreated samples using a reverse transcription-PCR-based, customized low-density array with 45 target genes of therapeutic interest. The gene expression of the untreated sample (which can be considered a baseline/static readout) was not predictive of gemcitabine efficacy in these tumors. Altogether, the only gene that differentiated sensitive versus resistant cases was polo-like kinase 1 (Plk1), showing >50% downregulation in sensitive cases and no change in the resistant cases. Inhibition of Plk1 by either small interfering RNA gene knockdown or with the Plk1 pathway modulator (ON 01910.Na) synergized with gemcitabine in gemcitabine-refractory in vitro models providing mechanistic proof of concept. In vivo experiments in gemcitabine-resistant xenografts showed synergistic activity decreasing cell proliferation and tumor regressions. A quantitative gene expression-based vulnerability assay identified Plk1 as a relevant target dictating the susceptibility of pancreatic cancer to gemcitabine. Dynamic interrogation of cancer has the potential to provide key information about mechanisms of resistance and to enhance individualization of treatment.
Highlights
MCT-1 oncoprotein accelerates p53 protein degradation via a proteosome pathway
MCT-1 gene and protein are downregulated by p53 To investigate whether p53 affected intrinsic MCT-1 gene activation, the non-small cell lung cancer H1299 (p53 null) cells were transfected with pCDNA vector alone or pCDNA-p53 to rebuild p53 function
The pGL3-MCT-1 promoter construct was introduced into the control H1299 cells that expressed with the vector alone, the wild-type p53, or the mutant p53 (Figure 1A)
Summary
MCT-1 oncoprotein accelerates p53 protein degradation via a proteosome pathway. Synergistic promotion of the xenograft tumorigenicity has been demonstrated in circumstance of p53 loss alongside MCT-1 overexpression. P53 binds to the consensus DNA sequence consisting of two copies of the 10-bp motif 5’-RRRC(A/T)(T/A)GYYY-3’, in which R is a purine and Y is a pyrimidine, separating by a 1-13 base pair (bp) junction [6,7,8]. These specific sequences are recognized in the p53 regulatory genes, such as Pirh2 [9], Cop1 [10], Waf-1/p21 [11], MDM2 [12], Bax [13], and PCNA [14]. Pirh, MDM2, and Cop are ubiquitin ligases implicated in
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