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Evaluating Alkaline Phosphatase-Instructed Self-Assembly of d‑Peptide Diesters for Selectively Inhibiting
Meihui Yi1, Gabriel Ashton-Rickardt1, Yuchen Qiao1
1Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, United States.
Abstract:
Hypoxia-driven adenosinergic signaling suppresses antitumor immunity and enables many tumors to evade cancer immunotherapy. Alkaline phosphatase (ALP) contributes to this immunosuppression by hydrolyzing extracellular adenosine triphosphate (ATP) to adenosine. Rather than inhibiting this broadly essential enzyme, we exploit elevated ALP activity in tumors as a tumor-specific trigger for enzyme-instructed self-assembly (EISA). Using a potent naphthalene-capped phosphopeptide diester precursor (1P), which exhibits in vivo efficacy as a starting point, we designed and synthesized a series of analogs (2P-15P) that vary the N-terminal capping group and/or the position of the phosphotyrosine trigger to explore structure-activity relationships. We evaluated these analogs for anticancer activity in ALP-overexpressing cancer cells (e.g., Saos-2), using ALP-low cells (e.g., HEK-293) as controls. One analog (6P) exhibited potent, selective cytotoxicity, with submicromolar GI50 values (∼0.3 μM) in ALP-high cancer cells. Notably, 6P demonstrated submicromolar GI90 values and surpassed the efficacy of cisplatin and paclitaxel against Saos-2 cells. These findings highlight the potential of rationally designed d-phosphopeptide diesters to enable ALP-responsive self-assembly and selectively inhibit the growth of ALP-overexpressing tumors. This strategy offers a promising platform for the development of supramolecular therapeutics targeting immunosuppressive tumor microenvironments.
Insights
We developed novel phosphopeptide diesters that self-assemble in tumors, selectively killing cancer cells. This enzyme-instructed self-assembly (EISA) strategy targets alkaline phosphatase (ALP) to overcome tumor immune evasion and enhance cancer immunotherapy.
Area of Science:
- Biochemistry
- Organic Chemistry
- Cancer Biology
Background:
- Hypoxia-driven adenosinergic signaling suppresses antitumor immunity, aiding tumor immune evasion.
- Alkaline phosphatase (ALP) promotes immunosuppression by converting extracellular adenosine triphosphate (ATP) to adenosine.
- Targeting ALP activity in tumors offers a strategy to disrupt this immunosuppressive mechanism.
Purpose of the Study:
- To design and synthesize novel phosphopeptide diester analogs for enzyme-instructed self-assembly (EISA).
- To exploit elevated tumor-specific alkaline phosphatase (ALP) activity as a trigger for EISA.
- To evaluate the anticancer activity and selectivity of these analogs in ALP-overexpressing cancer cells.
Main Methods:
- Synthesis of phosphopeptide diester analogs (2P-15P) with variations in capping groups and trigger positions.
- Evaluation of structure-activity relationships for anticancer efficacy.
- Assessment of cytotoxicity in ALP-high (Saos-2) and ALP-low (HEK-293) cell lines.
Main Results:
- Analog 6P demonstrated potent and selective cytotoxicity against ALP-high cancer cells, with submicromolar GI50 values (~0.3 μM).
- Compound 6P achieved submicromolar GI90 values, outperforming cisplatin and paclitaxel in Saos-2 cells.
- The study identified rationally designed d-phosphopeptide diesters capable of ALP-responsive self-assembly.
Conclusions:
- Developed phosphopeptide diesters enable ALP-responsive self-assembly for targeted cancer therapy.
- This EISA strategy selectively inhibits ALP-overexpressing tumors, offering a novel approach to combat immunosuppressive tumor microenvironments.
- The findings present a promising platform for supramolecular therapeutics in cancer immunotherapy.
