Toward improved models of human cancer

Biomimetic Design of Peptide Inhibitor to Block CD47/SIRPα Interactions

CD47 on the surface of tumor cells has become a research hot spot in immunotherapy and anticancer therapy, as it can bind to SIRPα protein on the surface of macrophages, which ultimately leads to immune escape of tumor cells. In the present study, molecular interactions between CD47 and human SIRPα proteins (including variant 1, V1 and variant 2, V2) were analyzed through molecular dynamics (MD) simulation and the molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) method. Hydrophobic interactions were found as the main driving force for the binding of CD47 on SIRPα. The residues including pyroglutamate acid (Z)1, L2, E35, Y37, E97, L101, and T102 of CD47 were identified with a significant favorable contribution to the binding of CD47 on SIRPα (both V1 and V2). Based on this, a peptide inhibitor library with the sequence ZLXRTLXEXY was designed (X represents the arbitrary residue of 20 standard amino acids) and then screened using molecular docking, MD simulations, and experimental validation. Finally, a peptide ZLIRTLHEWY was determined with high affinity with SIRPα from 8000 candidates, containing 6/10 residues favorable for the binding on SIRPα V1 and 8/10 residues favorable for the binding on SIRPα V2, which was thus considered to have potential anticancer function.

Hematogenous metastasis and tumor dormancy as concepts or dogma? The continuum of vessel co-option and angiotropic extravascular migratory metastasis as an alternative

It has been accepted for many years that tumor cells spread via the circulation to distant sites. The latency period between treatment and tumor recurrence has been attributed to dormant cells in distant organs that emerge and grow as metastatic tumors. These processes are accepted with an incomplete demonstration of their existence. Challenging such a well-established accepted paradigm is not easy as history as shown. An alternative or co-existing mechanism involving tumor cell migration along the outside of the vessels and co-option of the blood vessel has been studied for over 25 years and is presented. Several lines of data support this new mechanism of tumor spread and metastatic growth and is termed angiotropic extravascular migratory metastasis or EVMM. This slow migration along the outside of the vessel wall may explain the latency period between treatment and metastatic tumor growth. The reader is asked to be open to this possible new concept in how tumors spread and grow and the reason for this latency period. A full understanding of how tumors spread and grow is fundamental for the targeting of new therapeutics.

A Genome-Wide Screen Identifies PDPK1 as a Target to Enhance the Efficacy of MEK1/2 Inhibitors in NRAS Mutant Melanoma

Melanomas frequently harbor activating NRAS mutations. However, limited advance has been made in developing targeted therapy options for patients with NRAS mutant melanoma. MEK inhibitors (MEKi) show modest efficacy in the clinic and their actions need to be optimized. In this study, we performed a genome-wide CRISPR-Cas9-based screen and demonstrated that loss of phosphoinositide-dependent kinase-1 (PDPK1) enhances the efficacy of MEKi. The synergistic effects of PDPK1 loss and MEKi was validated in NRAS mutant melanoma cell lines using pharmacologic and molecular approaches. Combined PDPK1 inhibitors (PDPK1i) with MEKi suppressed NRAS mutant xenograft growth and induced gasdermin E-associated pyroptosis. In an immune-competent allograft model, PDPK1i+MEKi increased the ratio of intratumoral CD8+ T cells, delayed tumor growth, and prolonged survival; the combination treatment was less effective against tumors in immune-deficient mice. These data suggest PDPK1i+MEKi as an efficient immunostimulatory strategy against NRAS mutant melanoma.

SIGNIFICANCE

Targeting PDPK1 stimulates antitumor immunity and sensitizes NRAS mutant melanoma to MEK inhibition, providing rationale for the clinical development of a combinatorial approach for treating patients with melanoma.

Erratum: "Toward improved models of human cancer" [APL Bioeng. , 010901 (2021)]

[This corrects the article DOI: 10.1063/5.0030534.].