Abstract P2-01-04: The whole transcriptional landscape of circulating tumor cells compared to metastases in stage IV breast cancer

Background: Metastatic breast cancer (MBC) and the circulating cells (CTCs) leading to macrometastasis are inherently different than primary breast cancer, evolving under the selection pressure of systemic therapy. A better understanding of the tumor biology of CTCs compared to metastasis may shed light on treatment opportunities.

Methods: We performed whole transcriptome sequencing (RNA Seq) on fresh metastatic tumor biopsies (mets), CTCs, and peripheral blood (PB) from 21 newly diagnosed MBC patients. CTCs were harvested using the ANGLE Parsortix to isolate cells based on size and deformability. Data were analyzed for differential expression, pathways, single nucleotide variants (SNV), fusions, intrinsic subtype, and a CTC-mets shared gene signature was validated using data from The Cancer Genome Atlas (TCGA). Detailed clinical-pathological and treatment data was evaluated.

Results: CTCs as a group showed much stronger gene expression of oncogenes, stem cell genes, keratins and mesenchymal markers than did mets from the same patients. Matched patient comparisons for 66 potentially clinically actionable genes for 8/9 pathways showed no significant difference in gene expression targets between CTCs and mets on ANOVA, although fold-change did vary. Eight SNVs in the ESR1 gene (n=5 patients) and 5 SNVs in the HER2 gene (n=2 patients) were shared between CTCs and distant metastases.

Differential gene expression analysis identified a signature of 8870 genes that were statistically significantly correlated between CTCs and mets (FDR adjusted p<0.05). Ingenuity pathway analysis was applied to the list of genes shared between CTCs and mets, with analysis of canonical pathways and upstream regulators revealing numerous oncogenes and breast cancer related genes. The top upstream regulators of CTCs-mets were beta-estradiol, progesterone, FOXA1, HNRPA2B1 and HNF1A. The top 50 genes of this CTC-mets shared signature were prognostic of worse overall survival in the TCGA breast cancer dataset (p<0.001), which included 817 patients with a median follow-up of 59.5 months. Second time-point data for n=5 patients with subsequent PB draws 6 months after baseline is currently pending. Intrinsic subtyping of mets by either NanoString assays or RNA Seq were not concordant with intrinsic subtyping of CTCs by RNA Seq.

Four of 21 CTC samples showed strong whole transcriptome RPKM correlation with PB (R2)>0.9, however, 3/21 CTC samples showed strong whole transcriptome RPKM correlation with mets (R2)>0.8. The remainder showed low correlation with both. Coverage was 91.4X for CTCs, 140.2X for mets and 138.5X for PB.

Conclusions: We present the transcriptomic landscape of CTCs with comparison to metastases and peripheral blood all acquired prior to treatment of newly diagnosed Stage IV breast cancer. Multiple genes, including oncogenes and stem cell genes, were found with higher expression in CTCs versus metastases. When focusing on 66 known potentially clinically actionable genes in breast cancer, CTCs did not show significantly different patterns of expression than mets in terms of up-regulation versus down-regulation compared to PB. RNA Seq of CTCs may be utilized to identify molecular alterations that are potentially clinically actionable.

Citation Format: Ring A, Porras T, Campo D, Kaur P, Forte VA, Tripathy D, Lu J, Zada G, Wagle N, Wecsler JS, Lang JE. The whole transcriptional landscape of circulating tumor cells compared to metastases in stage IV breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-01-04.

Multicenter study of MTT and resazurin assays for testing susceptibility to first-line anti-tuberculosis drugs

OBJECTIVE

A multicentre evaluation was performed to assess two rapid low-cost methods, MTT (3-[4.5-dimethylthiazol-2-yl]-2.5-diphenyltetrazolium bromide) and resazurin assays, for testing the susceptibility of Mycobacterium tuberculosis to the first-line anti-tuberculosis drugs rifampicin (RMP), isoniazid (INH), ethambutol (EMB) and streptomycin (SM).

METHODS

Thirty coded M. tuberculosis strains were sent to seven laboratories located in Latin America, representing six countries. Each site performed the colorimetric assays, MTT and resazurin, blind for the first-line drugs RMP, INH, EMB and SM. The minimum inhibitory concentration results obtained were compared to the conventional proportion method on Lowenstein-Jensen medium.

RESULTS

After establishing the breakpoint concentrations, excellent results were obtained for RMP, INH and EMB, with levels of specificity and sensitivity of between 96% and 99%.

CONCLUSION

MTT and resazurin assays are promising, accessible new alternative methods for middle- and low-resource countries that need low-cost methods to perform rapid susceptibility testing of M. tuberculosis to key anti-tuberculosis drugs.

Cyclic nucleotides modulate store-mediated calcium entry through the activation of protein-tyrosine phosphatases and altered actin polymerization in human platelets

Agonists elevate the cytosolic calcium concentration in human platelets via a receptor-operated mechanism, involving both Ca(2+) release from intracellular stores and subsequent Ca(2+) entry, which can be inhibited by platelet inhibitors, such as prostaglandin E(1) and nitroprusside which elevate cAMP and cGMP, respectively. In the present study we investigated the mechanisms by which cAMP and cGMP modulate store-mediated Ca(2+) entry. Both prostaglandin E(1) and sodium nitroprusside inhibited thapsigargin-evoked store-mediated Ca(2+) entry and actin polymerization. However, addition of these agents after induction of store-mediated Ca(2+) entry did not affect either Ca(2+) entry or actin polymerization. Furthermore, prostaglandin E(1) and sodium nitroprusside dramatically inhibited the tyrosine phosphorylation induced by depletion of the internal Ca(2+) stores or agonist stimulation without affecting the activation of Ras or the Ras-activated phosphatidylinositol 3-kinase or extracellular signal-related kinase (ERK) pathways. Inhibition of cyclic nucleotide-dependent protein kinases prevented inhibition of agonist-evoked Ca(2+) release but it did not have any effect on the inhibition of Ca(2+) entry or actin polymerization. Phenylarsine oxide and vanadate, inhibitors of protein-tyrosine phosphatases prevented the inhibitory effects of the cGMP and cAMP elevating agents on Ca(2+) entry and actin polymerization. These results suggest that Ca(2+) entry in human platelets is directly down-regulated by cGMP and cAMP by a mechanism involving the inhibition of cytoskeletal reorganization via the activation of protein tyrosine phosphatases.