S100A14: A novel negative regulator of cancer stemness and immune evasion by inhibiting STAT3-mediated programmed death-ligand 1 expression in colorectal cancer.

BACKGROUND: Programmed death-ligand 1 (PD-L1) has functional roles in cancer stem-like cell (CSC) phenotypes and chemoresistance besides immune evasion. Chemotherapy is a common treatment choice for colorectal cancer (CRC) patients; however, chemoresistance limits its effectiveness of treatment. METHODS: We examined the role of S100A14 (SA14) in CRC by adopting PD-L1high subpopulations within CRC cell lines and patient tumours, by establishing PD-L1high chemoresistant CRC sublines through prolonged exposure to 5-fluorouracil/oxaliplatin-based chemotherapy in vitro and in vivo, and by analysing a public database. RESULTS: We identified a novel function of SA14 as a regulator of immune surveillance, major CSC phenotypes, and survival capacity under hostile microenvironments, including those harbouring chemotherapeutics, and as a prognostic biomarker in CRC. Mechanistically, SA14 inhibits PD-L1 expression by directly interacting with signal transducer and activator of transcription 3 (STAT3) and inducing its proteasome-mediated degradation. While gain-of-SA14 causes loss of PD-L1 expression and tumourigenic potential and sensitisation to chemotherapy-induced apoptosis in chemoresistant CRC cells, loss-of-SA14 causes increases in PD-L1 expression, tumourigenic potential, and chemoresistance in vitro and in vivo. We further show that a combinatorial treatment with chemotherapy and recombinant SA14 protein effectively induces apoptosis in PD-L1high chemoresistant CRC cells. CONCLUSIONS: Our results suggest that SA14-based therapy is an effective strategy to prevent tumour progression and that SA14 is a predictive biomarker for anti-PD-L1 immunotherapy and chemotherapy in combination.

Application of bioengineered elastin-like polypeptide-based system for targeted gene delivery in tumor cells.

Successful gene delivery depends on the entry of negatively charged DNAs and oligonucleotides across the various barriers of the tumor cells and localization into the nucleus for its transcription and protein translation. Here, we have reported a thermal responsive self-assemble and highly biocompatible, targeted ELP-based gene delivery system. These systems consist of cell-penetrating peptides, Tat and single or multiple repeats of IL-4 receptor targeting peptide AP-1 along the backbone of ELP. Cell-penetrating peptides were introduced for nuclear localization of genes of interest, AP-1 for targeting IL-4R highly expressed tumor cells and ELP for stable condensation favoring protection of nucleic acids. The designed multidomain fusion ELPs referred to as Tat-ELP, Tat-A1E28 and Tat-A4V48 were employed to generate formulation with pEGFP-N1. Profound formulation of stable complexes occurred at different molar ratios owing to electrostatic interactions of positively charged amino acids in polymers with negatively charged nucleic acids. Among the complexes, Tat-A4V48 containing four copies of AP-1 showed maximum complexation with pEGFP-N1 in lower molar ratio. The polymer-pEGFP complexes were further analyzed for its transfection efficiency in different cancer cell lines. Both the targeted polymers, Tat-A4V48 and Tat-A1E28 upon transfection displayed significant EGFP-expression with low toxicity in different cancer cells. Therefore, both Tat-A4V48 and Tat-A1E28 can be considered as novel transfection system for successful gene delivery with therapeutic applications.

Targeting of Cisplatin-Resistant Melanoma Using a Multivalent Ligand Presenting an Elastin-like Polypeptide.

Acquired drug resistance is a common occurrence and the main cause of melanoma treatment failure. Melanoma cells frequently developed resistance against cisplatin during chemotherapy, and thus, targeting delivery systems have been devised to decrease drug resistance, increase therapeutic efficacy, and reduce side effects. We genetically engineered a macromolecular carrier using the recursive directional ligation method that specifically targets cisplatin-resistant (Cis-R) melanoma. This carrier is composed of an elastin-like polypeptide (ELP) and multiple copies of Cis-R melanoma-targeting ligands (M-peptide). The designed M16E108 contains 16 targeting ligands incorporated within an ELP and has an ideal thermal phase transition at 39 °C. When treated to melanoma cells, M16E108 specifically accumulated in Cis-R B16F10 melanoma cells and accumulated to a lesser extent in parental B16F10 cells. Consistently, M16E108 exhibited efficient homing and longer retention in tumor tissues in Cis-R melanoma-bearing mice than in parental B16F10 melanoma-bearing mice. Thus, M16E108 was found to display considerable potential as a novel agent that specifically targets cisplatin-resistant melanoma.