RarePlex® PD-L1 CTC Panel Kit
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RarePlex PD-L1 (Programmed Death Ligand) CTC Panel Kit



Tumors can induce immune suppression by modulating immune responses via immune checkpoint pathways that rely on the programmed cell death protein 1 (PD-1) binding to its ligand, programmed death ligand 1 (PD-L1).1 The interaction of PD-L1 on tumor cells with its receptor PD-1 on activated T cells, is one of the main pathways exploited by cancer cells for immune evasion. PD-L1 expression has been observed in a wide variety of tumors and has been associated with poor clinical outcomes.2

The binding of PD-L1 to PD-1 on activated T cells also causes T-cell exhaustion2, which is characterized by the stepwise and progressive loss of T-cell functions.3 Blocking the binding of PD-L1 to PD-1 with an immune checkpoint inhibitor drug (anti-PD-L1 or anti-PD-1) can re-activate the T cells to kill tumor cells once again.

How Rarecyte’s Programmed Death Ligand CTC Assay Works to Detect Cancer Cells

RareCyte’s PD-L1 circulating tumor cell (CTC) assay provides highly accurate, repeatable, and precise results for circulating tumor cell counting and measuring PD-L1 biomarker expression, and is suitable for use in large, multi-center clinical trials. The assay includes processing blood to slides with the AccuCyte® Sample Preparation System followed by staining with the RarePlex 0912-VB PD-L1 CTC Panel Kit and imaging on a CyteFinder® Instrument. Machine learning enabled analysis and scoring maximizes reviewer concordance.

This PD-L1 assay is deployed on RareCyte’s circulating tumor cell analysis platform with:

  • Simple processing of blood to slides for sample banking
  • Convenient pause points in workflow enable sample control and transport
  • Flexibility in sample handling – processing and analysis may be performed at the same site or at a separate clinical research laboratory when desired
  • Extensive validation and highly automated process yield accurate and highly reproducible results
  • Worldwide network of contract research organizations (CROs) to support global clinical trials

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Clinical lung cancer sample with Programmed Death Ligand Panel Kit

Clinical lung cancer sample stained with the PD-L1 CTC Panel Kit

Clinical lung cancer sample stained with the PD-L1 CTC Panel Kit. Merge represents a composite image of CK/EpCAM, Nuclei, and CD45.
Scale bar represents 10μm.
Samples of the PD-L1 CTC Panel Kit
SW900 (PD-L1 high), H1650 (PD-L1 low), and HAP-1 (PD-L1 negative) cell lines are shown. The top row represents a merge image where Nuclei = blue, CD45 = green, and CK/EpCAM = magenta. The PD-L1 localization in the bottom row matches expected expression levels. Speckled PD-L1 signal surrounding the mCTCs and WBCs is consistent with staining of background platelets, which are known to express PD-L1 protein (Rolfes V, et al. Oncotarget 9(44):27460).
Scale bar represents 10μm.
Distribution of PD-L1 MFI for mCTC across the 5 slide replicates per cell line
Distribution of PD-L1 MFI for mCTC across the 5 slide replicates per cell line for stainer run 1 (left), 2, (center), and 3 (right). Threshold dotted line at MFI=500 is used to determine biomarker expression status on a per-cell basis.

Additional resources for the RarePlex PD-L1 Panel Kit

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  • Dermani FK, Samadi P, Rahmani G, Kohlan AK, Najafi R. PD-1/PD-L1 immune checkpoint: Potential target for cancer therapy. J Cell Physiol. 2019;234(2):1313-1325. doi:10.1002/jcp.27172
  • Jiang Y, Chen M, Nie H, Yuan Y. PD-1 and PD-L1 in cancer immunotherapy: clinical implications and future considerations. Hum Vaccin Immunother. 2019;15(5):1111-1122. doi:10.1080/21645515.2019.1571892Liu J, Chen Z, Li Y, Zhao W, Wu J and Zhang Z (2021) PD-1/PD-L1 Checkpoint Inhibitors in Tumor Immunotherapy. Front. Pharmacol. 12:731798. doi: 10.3389/fphar.2021.731798
  • Wang X, Teng F, Kong L, Yu J. PD-L1 expression in human cancers and its association with clinical outcomes. Onco Targets Ther. 2016;9:5023-5039. Published 2016 Aug 12. doi:10.2147/OTT.S105862

Working with the RarePlex® Developer Kit

Presented by Edward Lo, Ph.D., Scientist, Assay Development Lead
Developer technology from RareCyte enables you to add up to two custom biomarkers to your CTC assay. This 5 minute video will walk you through each step of the Developer process and provide examples of completed assays.


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