Evaluation of Monocarboxylate Transporter 4 (MCT4) Expression and Its Prognostic Significance in Circulating Tumor Cells From Patients With Early Stage Non-Small-Cell Lung Cancer

Purpose: Monocarboxylate transporter 4 (MCT4) can influence the amount of lactate in the tumor microenvironment and further control cancer cell proliferation, migration, and angiogenesis. We investigated for the first time the expression of MCT4 in circulating tumor cells (CTCs) derived from early stage Non-Small Cell Lung Cancer patients (NSCLC) and whether this is associated with clinical outcome.

Experimental Design: A highly sensitive RT-qPCR assay for quantification of MCT4 transcripts was developed and validated and applied to study MCT4 expression in CTC isolated through the Parsortix size-dependent microfluidic device from 53 and 9 peripheral blood (PB) samples of NSCLC patients at baseline (pre-surgery) and at relapse, respectively, as well as the “background noise” was evaluated using peripheral blood samples from 10 healthy donors (HD) in exactly the same way as patients.

Results:MCT4 was differentially expressed between HD and NSCLC patients. Overexpression of MCT4 was detected in 14/53 (26.4%) and 3/9 (33.3%) patients at baseline and at progression disease (PD), respectively. The expression levels of MCT4 was found to increase in CTCs at the time of relapse. Kaplan-Meier analysis showed that the overexpression of MCT4 was significantly (P = 0.045) associated with progression-free survival (median: 12.5 months, range 5–31 months).

Conclusion:MCT4 overexpression was observed at a high frequency in CTCs from early NSCLC patients supporting its role in metastatic process. MCT4 investigated as clinically relevant tumor biomarker characterizing tumor aggressiveness and its potential value as target for cancer therapy. We are totally convinced that MCT4 overexpression in CTCs merits further evaluation as a non-invasive circulating tumor biomarker in a large and well-defined cohort of patients with NSCLC.

Nuclease-Assisted Minor Allele Enrichment Using Overlapping Probes-Assisted Amplification-Refractory Mutation System: An Approach for the Improvement of Amplification-Refractory Mutation System-Polymerase Chain Reaction Specificity in Liquid Biopsies

Allele-specific polymerase chain reaction (PCR) (amplification-refractory mutation system, ARMS) is one of the most commonly used methods for mutation detection. However, a main limitation of ARMS-PCR is the false positive results obtained due to nonspecific priming that can take place with wild-type (WT) DNA, which often precludes detection of low-level mutations. To improve the analytical specificity of ARMS, we present here a new technology, NAPA: NaME-PrO-assisted ARMS, that overcomes the ARMS deficiency by adding a brief enzymatic step that reduces wild-type alleles just prior to ARMS. We performed this technology for the simultaneous detection of two hot-spot PIK3CA mutations (E545 K and H1047R) in circulating tumor cells (CTCs) and cell free DNA (cfDNA). The developed protocol could simultaneously detect mutation-allelic-frequency of 0.5% for PIK3CA exon 9 (E545 K) and 0.1% for PIK3CA exon 20 (H1047R) with high specificity. We further compared the developed NAPA assay with (a) ddPCR considered as the gold standard and (b) our previous assay based on the combination of allele-specific, asymmetric rapid PCR, and melting analysis. Our data show that the newly developed NAPA assay gives consistent results with both these assays (p = 0.001). The developed assay resolves the false positive signals issue derived through classic ARMS-PCR and provides an ideal combination of speed, accuracy, and versatility and should be easily applicable in routine diagnostic laboratories.

Abstract 497: PIK3CA mutational status in circulating tumor cells (CTCs) and corresponding circulating tumor DNA in breast cancer patients

AIMS: Molecular characterization of Circulating Tumor Cells (CTCs) and analysis of circulating tumor DNA (ctDNA) in cancer patients holds promise as an extremely powerful and reliable non-invasive clinical tool for the individual molecular profiling of each patient in real time. The phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway is implicated in human cancers, and somatic mutations in the p110α catalytic subunit of PI3K, are very frequent and play a crucial role in response to molecular targeted therapies in breast cancer. In this study, we analyzed PIK3CA hotspot mutations (1633 G>A, 3140 A>G) in CTCs and corresponding ctDNA of early and metastatic breast cancer patients. We also examined whether there is a correlation between the presence of PIK3CA mutations in CTCs and ctDNA.

METHODS: We used our highly sensitive methodology for the detection of PIK3CA hotspot mutations in exons 9 (1633 G>A) and 20 (3140 A>G), based on a combination of allele-specific PCR, asymmetric rapid PCR and high resolution melting analysis (HRMA) (Markou et al, CCR 2014). We analyzed PIK3CA hotspot mutations in the EpCAM-positive CTCs fraction and the corresponding plasma samples of: i) a group of 19 patients with operable breast cancer, ii) a group of 40 breast cancer patients with verified metastasis and iii) 30 healthy female volunteers. All ctDNA samples (extracted from 2 ml plasma) were examined for their DNA quality; to verify DNA quality, primers specific for the wild type in exactly the same PIK3CA gene region for exon 9 were used to assess for hotspots mutations. The mutation status of PIK3CA gene in ctDNA samples was detected by the developed methodology exactly as previously described. All samples were analyzed in triplicate.

RESULTS: The assay is highly sensitive as it can detect 0.05% of mutated dsDNA in the presence of 99.95% wtDNA for both exons (9 and 20) and highly specific (0/30 healthy donors). PIK3CA hotspot mutations were identified in ctDNA in 12/40 (30%) of metastasis-verified breast cancer patients and 4/19 (21%) of operable breast cancer patients. In metastasis-verified breast cancer patients, the concordance between EpCAM- positive CTCs and ctDNA for 1633 G>A mutation was 72.5%, whereas the corresponding concordance for the 3140 A>G mutation was 97.5%. In operable breast cancer patients, the concordance between EpCAM-positive CTCs and ctDNA for the 1633 G>A mutation was 80%, whereas the corresponding concordance for the 3140 A>G mutation was 100%.

CONCLUSIONS: Detection of PIK3CA hotspot mutations in EpCAM-positive CTCs and corresponding ctDNA has shown a correlation both in metastasis-verified and operable breast cancer patients. We will further evaluate our findings in a large cohort of patients before and after treatment, to evaluate response to molecular targeted therapies in breast cancer.

Citation Format: Elena Tzanikou, Athina Markou, Nikos Malamos, Vasilis Georgoulias, Evi S. Lianidou. PIK3CA mutational status in circulating tumor cells (CTCs) and corresponding circulating tumor DNA in breast cancer patients. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 497.