Pictilisib and nutrient stress synergize to induce methuosis via PI(4,5)P2-dependent macropinocytic dysregulation in cancer cells

Sep 22, 2026

PI3K inhibition combined with nutrient stress triggers methuosis, a non-apoptotic programmed cell death marked by dysregulated macropinosomes. The effect selectively targets PI3K-aberrant cancer cells that preserve macropinocytic uptake during treatment. Methuosis vacuoles arise from macropinosomes retaining endosomal markers but failing lysosomal fusion. PI3K blockade causes PI(4,5)P2 accumulation on internal membranes, impairing ion channels, provoking aquaporin-1-mediated water influx, and driving vacuolar expansion and cell death. Dietary restriction synergizes with Pictilisib to suppress xenograft tumors and intensify intratumoral vacuolization.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages15

Reading Time38 min

AccessFree to download

Introduction

PI3K pathway and cancer therapy limits

Non-apoptotic cell death and methuosis

Results

PI3K inhibition with nutrient stress induces methuosis

Role of macropinocytic uptake and PI(4,5)P2 accumulation

Ion dysregulation and aquaporin-1 water influx

Autophagy and xenograft synergy with dietary restriction

[www.nature.com/cddis](www.nature.com/cddis) ARTICLE OPEN Pictilisib and nutrient stress synergize to induce methuosis via PI(4,5)P2-dependent macropinocytic dysregulation in cancer cells Xuefei Wang 1,7, Xiaolin Sang 2,7, Yuemei Wen3, Xingming Liao3, Jiao Liu1, Tiezheng Zheng 1,3, Tianming Xing3, Min Wang1, Dong An1, Xining Zhang 1, Xiuling Li 4,5 ✉, Xinmiao Liang 4,5 ✉, Pixu Liu 2,3 ✉ and Hailing Cheng 1,6 ✉ © The Author(s) 2026 | | | | | | | | --- | --- | --- | --- | --- | --- | | | Aberrant phosphatidylinositol 3-kinase (PI3K) activation drives many cancers, but PI3K inhibitors like Pictilisib often induce cytostasis rather than cytotoxicity, limiting their therapeutic potential. Here we demonstrate that PI3K inhibition combined with nutrient stress triggers methuosis, a non-apoptotic form of programmed cell death characterized by dysregulated macropinosomes. This response occurs selectively in PI3K-aberrant cancer cells that maintain macropinocytic uptake despite PI3K inhibition. Methuosis-associated vacuoles originate from macropinosomes that retain endosomal markers but fail to undergo lysosomal fusion. Active macropinocytic uptake is essential for methuosis, as demonstrated by suppression with EIPA and Baﬁlomycin A1, whereas the AKT inhibitor MK2206 has no effect, establishing that direct PI3K inhibition, rather than AKT signaling, is required. Mechanistically, PI3K blockade prevents conversion of phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2) tophosphatidylinositol (3,4,5)-trisphosphate (PI(3,4,5)P3) causing PI(4,5)P2 to accumulate on internalizing macropinosomal membranes. This aberrant PI(4,5)P2 enrichment impairs ion channel function across multiple channel families, disrupting intracellular osmotic balance. Ion dysregulation triggers aquaporin-1-mediated water inﬂux, driving catastrophic vacuolar expansion and cell death. Although Pictilisib activates pro-survival autophagy, this fails to prevent methuosis-mediated cytotoxicity. In xenograft models, dietary restriction synergizes with Pictilisib to suppress tumor growth, correlating with pronounced intratumoral vacuolization. These ﬁndings reveal that combining PI3K inhibition with nutrient restriction converts cytostatic responses into methuosis-driven cytotoxicity via PI(4,5)P2-dependent macropinocytic dysregulation, providing a rational pharmacologic-dietary strategy to enhance PI3K-targeted cancer efﬁcacy. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Cell Death and Disease (2026) 17:752 ; [https://doi.org/10.1038/s41419-026-08994-6](https://doi.org/10.1038/s41419-026-08994-6) | | | | | | | | | | | | INTRODUCTION The phosphatidylinositol 3-kinase (PI3K) pathway is a critical regulator of essential cellular processes, including proliferation, survival, and metabolism [1] . The pathway operates through the phosphorylation of phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2) to generate phosphatidylinositol (3,4,5)-trisphosphate (PI(3,4,5)P3), which recruits and activates downstream effectors including AKT via PDK1, thereby promoting cell growth and survival [2] . Dysregulation of PI3K signaling is among the most frequently occurring oncogenic alterations in human cancers, typically driven by activating mutations in PIK3CA (e.g. E545K or H1047R) or loss-of-function mutations in the tumor suppressor PTEN [3–5] . Given this central role in oncogenesis, PI3K has emerged as an attractive target for cancer therapy. However, clinical development of PI3K inhibitors, including the pan-class I agent Pictilisib, has been hampered by limited efﬁcacy as monotherapies or combination regimens. These agents typically induce cytostasis (cell cycle arrest) rather than c

FAQs

What cellular death mechanism does Pictilisib plus nutrient stress induce?

It induces methuosis, a non-apoptotic cell death characterized by excessive cytoplasmic vacuolization from dysregulated macropinocytosis.

Why does the effect depend on PI(4,5)P2 and macropinocytic uptake?

Direct PI3K inhibition prevents PI(4,5)P2 conversion to PI(3,4,5)P3, leading to PI(4,5)P2 buildup on macropinosomal membranes and disrupting downstream ion/channel regulation. Active macropinocytic uptake is essential, as blocking uptake suppresses methuosis.

How does nutrient restriction enhance tumor suppression with Pictilisib?

Dietary restriction synergizes with Pictilisib in xenograft models to suppress tumor growth, correlating with pronounced intratumoral vacuolization.

Sep 22, 2026

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