Yuki Nakamura

Q: How did the anthor address the question?

■Step1 1. Discovery of the BBB-like vascular gate (BVG) in SCLC. Using ICI-treated patient transcriptome datasets and SCLC patient tissue samples, they demonstrated that SCLC vasculature exhibits blood-brain barrier (BBB)-like features. They also showed that SCLC exhibits similar characteristics in mouse models, and that SCLC tumor cells form a BBB-like vascular gate (BVG) that blocks T-cell infiltration. ■Step2 2. The BVG is induced by SCLC tumor cells through the ASCL1-IGFBP5-IGF1R axis. Through transcriptomic analysis of SCLS tumor tissue, they identified ASCL1 as a gene correlated with the BVG gene signature and confirmed BVG formation in ASCL1+ SCLC tumor tissue histologically. Since BVG was not formed in mice transplanted with ASCL1-deficient SCLC tumor cells, they identified ASCL1 as a regulator of BVG formation. Using IGFBP5-deficient SCLC tumor cells—which are downstream of ASCL1—they determined that the ASCL1-IGFBP5-IGF1R axis regulates BVG formation. Furthermore, using tumor tissues in which ASCL1 and IGFBP5 were overexpressed, they confirmed that these factors are both necessary and sufficient for BVG formation. ■Step3 3. Targeting the ASCL1-IGFBP5-IGF1R axis enhances immunotherapy efficacy in SCLC. In a mouse model, genetic deficiency of IGFBP5 and IGF1R inhibitors each demonstrated synergistic effects with anti-PD-1 therapy.

kawaokashinpei3
Jul 7
2 min read

Selected journal : Cell

A blood-brain barrier-like vascular gate limits immunotherapy efficacy in neuroendocrine cancers

https://doi.org/10.1016/j.cell.2026.04.017

What is the main question of the paper?

Why Does SCLC (Small Cell Lung Carcinoma) develop resistance to immune checkpoint inhibitors?

How did the anthor address the question?

■Step1

1. Discovery of the BBB-like vascular gate (BVG) in SCLC.

Using ICI-treated patient transcriptome datasets and SCLC patient tissue samples, they demonstrated that SCLC vasculature exhibits blood-brain barrier (BBB)-like features. They also showed that SCLC exhibits similar characteristics in mouse models, and that SCLC tumor cells form a BBB-like vascular gate (BVG) that blocks T-cell infiltration.

■Step2

2. The BVG is induced by SCLC tumor cells through the ASCL1-IGFBP5-IGF1R axis.

Through transcriptomic analysis of SCLS tumor tissue, they identified ASCL1 as a gene correlated with the BVG gene signature and confirmed BVG formation in ASCL1+ SCLC tumor tissue histologically. Since BVG was not formed in mice transplanted with ASCL1-deficient SCLC tumor cells, they identified ASCL1 as a regulator of BVG formation. Using IGFBP5-deficient SCLC tumor cells—which are downstream of ASCL1—they determined that the ASCL1-IGFBP5-IGF1R axis regulates BVG formation. Furthermore, using tumor tissues in which ASCL1 and IGFBP5 were overexpressed, they confirmed that these factors are both necessary and sufficient for BVG formation.

■Step3

3. Targeting the ASCL1-IGFBP5-IGF1R axis enhances immunotherapy efficacy in SCLC.

In a mouse model, genetic deficiency of IGFBP5 and IGF1R inhibitors each demonstrated synergistic effects with anti-PD-1 therapy.

What is the “strength” of the paper?

This study identifies a histological feature called BVG as the cause of SCLC resistance to immune checkpoint inhibitors, and its reasoning—from the identification of the regulatory factor to the demonstration of synergistic effects with immune checkpoint inhibitors—is straightforward and easy to understand. Another strength of this study is that the safety of the regulatory factor inhibitor (IGF1R inhibitor) has already been established in clinical settings, suggesting that its clinical application in combination therapy with immune checkpoint inhibitors is imminent.

Comment

I think the most unique part is that this paper found a completely opposite vascular feature in this cancer. While other tumors have leaky vessels, this paper discovered that SCLC actively builds a tight blood-brain barrier-like gate. The strategy to break this tight barrier instead of fixing leaky vessels is highly innovative.

Comment by Xiaoran Ma