Highly Specific Targeting and Imaging of Live Cancer Cells by Using a Peptide Probe Developed from Rationally Designed Peptides

Abstract

Specific detection and in vivo tracing of cancer biomarkers are important for cancer analysis. In this work, a simple and effective strategy for developing peptide probes was established. Peptides were rationally designed by using an antisense peptide approach directed towards an extracellular fragment (EL2) of a novel tumor-related protein LAPTM4B. Positional-scanning and stepwise affinity screening was employed to obtain an optimal peptide AP2H (IHGHHIISVG). The dissociation constant between the two small peptides, AP2H and the target EL2, was 5.51 μM under physiological conditions. Fluorescence imaging assays indicated that AP2H can recognize live hepatoma cells by targeting the LAPTM4B protein on the cell surface with high specificity, low cytotoxicity and desirable cell penetrability. Compared to negative control cells, AP2H could differentiate cells with different expression levels of LAPTM4B. The screened peptide probe for molecular signatures of cancer cells, based on targeting the LAPTM4B protein, has potential applications in cancer diagnosis and targetable drug delivery.

Tetraphenylethylene Conjugated with a Specific Peptide as a Fluorescence Turn‐On Bioprobe for the Highly Specific Detection and Tracing of Tumor Markers in Live Cancer Cells

“…[23b] In order to further acquire the three-dimensional subcellular distribution of the target LAPTM4B protein, a Zstacking scan was employed to analyze TPE-AP2H-treated cells ( Figure S8 in the Supporting Information). Compared with that obtained in the previous work with a fluorescein isothiocyanate (FITC) probe, [18] a high-contrast and strong fluorescence signal was visualized for the TPE-AP2H-stained LAPTM4B protein on the cell membrane. From these results, it can be anticipated that the detection sensitivity can be significantly benefited by the AIE property of the TPE framework.…”

“…Such a pH-responsive binding characteristic is well consistent with the results from an affinity chromatography approach. [18] This may be attributed to the presence of the three histidine residues in AP2H, which play an important role in the interactions and act as a switching tool responding to external pH conditions. [18,22] The reinforced AIE effect at lower pH values makes the bioprobe more promising for sensitively recognizing cancer cells by responding to the acidic tumor microenvironment.…”

“…[18] This may be attributed to the presence of the three histidine residues in AP2H, which play an important role in the interactions and act as a switching tool responding to external pH conditions. [18,22] The reinforced AIE effect at lower pH values makes the bioprobe more promising for sensitively recognizing cancer cells by responding to the acidic tumor microenvironment. In fact, this agrees well with the observation that brighter fluorescence images were detected after incubation of TPE-AP2H with cancer cells in acidic conditions (see below).…”

“…The molecular design is based on the following considerations. 1) AP2H can specifically bind the hydrophilic extracellular loop (EL2, PYRDDVMSVN; MW=1194.5) of lysosomal protein transmembrane 4 beta (LAPTM4B),18 which was found to overexpress in the majority of solid tumors, including carcinomas of the liver, lung, breast, cervix, and ovary 19. This broad‐spectrum characteristic makes LAPTM4B a unique biomarker for solid tumors.…”

Far-red/near-infrared fluorescence light-up probes for specific in vitro and in vivo imaging of a tumour-related protein

“…Lysosomal protein transmembrane 4 beta (LAPTM4B) is a vital biomarker for many solid tumours 27 28 29 . Detection and imaging of the emergence and localization of LAPTM4B proteins will significantly indicate the cancer occurrence, treatment efficacy and prognosis 15 30 31 .…”