Cell surface binding, uptaking and anticancer activity of L-K6, a lysine/leucine-rich peptide, on human breast cancer MCF-7 cells

Abstract

Cell surface binding and internalization are critical for the specific targeting and biofunctions of some cationic antimicrobial peptides (CAPs) with anticancer activities. However, the detailed cellular process for CAPs interacting with cancer cells and the exact molecular basis for their anticancer effects are still far from being fully understood. In the present study, we examined the cell surface binding, uptaking and anti-cancer activity of L-K6, a lysine/leucine-rich CAP, in human MCF-7 breast cancer cells. We found that L-K6 preferentially interact with MCF-7 cells. This tumor-targeting property of L-K6 might be partially due to its interactions with the surface exposed and negatively charged phosphatidylserine. Subsequently, L-K6 could internalize into MCF-7 cells mainly through a clathrin-independent macropinocytosis, without significant cell surface disruption. Finally, the internalized L-K6 induced a dramatic nuclear damage and MCF-7 cell death, without significant cytoskeleton disruption and mitochondrial impairment. This cytotoxicity of L-K6 against MCF-7 cancer cells could be further confirmed by using a mouse xenograft model. In summary, all these findings outlined the cellular process and cytotoxicity of L-K6 in MCF-7 cancer cells, and might help understand the complicated interactions between CAPs and cancer cells.

Screening and characterization of a novel high‐efficiency tumor‐homing cell‐penetrating peptide from the buffalo cathelicidin family

“…The detected intracellular fluorescence intensity of EGFP‐CAT was 3‐6 times that of EGFP‐LL37, EGFP‐IL, EGFP‐L‐K6, and EGFP‐TAT (Figure D). This result indicates that the cell‐penetrating ability of CAT is significantly higher than that of other reported AMP‐derived CPPs, even higher than the classical CPP TAT. Therefore, we have identified a novel AMP‐derived CPP with high penetration efficiency from the buCATHL4 family.…”

“…Similarly, IL is a 13 amino acid bovine‐derived AMP that has been shown to significantly promote the gene transfer of polycationic vectors . Another AMP‐derived CPP is L‐K6, a natural cationic AMP isolated from the skin secretions of the Chinese brown frog ( Rana chensinensis ), which could be internalized into MCF‐7 cells mainly through clathrin‐independent macropinocytosis without significant cell surface disruption . Furthermore, it has been reported that some AMPs can selectively penetrate tumor cells, for example, buforin IIb, which is a cell‐penetrating AMP that showed selective cytotoxicity against tumor cells .…”

“…2,17 Some AMPs have been screened and developed as new CPPs or have been identified to have cell-penetrating ability, such as LL37, indolicidin (IL) and L-K6. [18][19][20][21][22][23][24] LL37 is a 37 amino acid-long AMP derived from the human cathelicidin family. 18 LL37 showed CPP properties by mediating the delivery of a noncovalent complex with a fluorescently labeled oligonucleotide into eukaryotic cells.…”

“…[20][21][22] Another AMP-derived CPP is L-K6, a natural cationic AMP isolated from the skin secretions of the Chinese brown frog (Rana chensinensis), 23 which could be internalized into MCF-7 cells mainly through clathrin-independent macropinocytosis without significant cell surface disruption. 24 Furthermore, it has been reported that some AMPs can selectively penetrate tumor cells, for example, buforin IIb, which is a cell-penetrating AMP that showed selective cytotoxicity against tumor cells. 25 These reports confirm that AMPs could be an important source for the screening and discovery of novel CPPs for the development of future drug delivery systems in vivo due to their structural similarities with CPPs.…”

Antitumor activity of RT2 peptide derived from crocodile leukocyte peptide on human colon cancer xenografts in nude mice

“…Several studies have reported that the anticancer activity of peptides can cause DNA damage. Internalization of L‐K6 (lysine/leucine‐rich peptide) induced dramatic nuclear damage and MCF‐7 breast carcinoma cell death without significant cytoskeleton disruption . Other peptides, such as gaegurin 6 and PTP7, have anticancer activity against human cancer cells without cytotoxicity against peripheral blood mononuclear cells and minimal hemolytic activity .…”