Therapeutic implications of activating noncanonical PIK3CA mutations in head and neck squamous cell carcinoma
Nan Jin, … , Daniel E. Johnson, Jennifer R. Grandis
Nan Jin, … , Daniel E. Johnson, Jennifer R. Grandis
Published November 15, 2021
Citation Information: J Clin Invest. 2021;131(22):e150335. https://doi.org/10.1172/JCI150335.
View: Text | PDF
Research Article Oncology

Therapeutic implications of activating noncanonical PIK3CA mutations in head and neck squamous cell carcinoma

Abstract

Alpelisib selectively inhibits the p110α catalytic subunit of PI3Kα and is approved for treatment of breast cancers harboring canonical PIK3CA mutations. In head and neck squamous cell carcinoma (HNSCC), 63% of PIK3CA mutations occur at canonical hotspots. The oncogenic role of the remaining 37% of PIK3CA noncanonical mutations is incompletely understood. We report a patient with HNSCC with a noncanonical PIK3CA mutation (Q75E) who exhibited a durable (12 months) response to alpelisib in a phase II clinical trial. Characterization of all 32 noncanonical PIK3CA mutations found in HNSCC using several functional and phenotypic assays revealed that the majority (69%) were activating, including Q75E. The oncogenic impact of these mutations was validated in 4 cellular models, demonstrating that their activity was lineage independent. Further, alpelisib exhibited antitumor effects in a xenograft derived from a patient with HNSCC containing an activating noncanonical PIK3CA mutation. Structural analyses revealed plausible mechanisms for the functional phenotypes of the majority of the noncanonical PIK3CA mutations. Collectively, these findings highlight the importance of characterizing the function of noncanonical PIK3CA mutations and suggest that patients with HNSCC whose tumors harbor activating noncanonical PIK3CA mutations may benefit from treatment with PI3Kα inhibitors.

Authors

Nan Jin, Bhumsuk Keam, Janice Cho, Michelle J. Lee, Hye Ryun Kim, Hayarpi Torosyan, Natalia Jura, Patrick K.S. Ng, Gordon B. Mills, Hua Li, Yan Zeng, Zohar Barbash, Gabi Tarcic, Hyunseok Kang, Julie E. Bauman, Mi-Ok Kim, Nathan K. VanLandingham, Danielle L. Swaney, Nevan J. Krogan, Daniel E. Johnson, Jennifer R. Grandis

×

Figure 3

Functional characterization of all 32 noncanonical PIK3CA mutations in the HNSCC serum-dependent model.

Options: View larger image (or click on image) Download as PowerPoint
Functional characterization of all 32 noncanonical PIK3CA mutations in t...
(A) Generation of isogenic PCI-52-SD1 cells expressing the 32 noncanonical PIK3CA mutations. Immunoblotting with anti-FLAG was used to confirm expression of LUC, WT p110α, or the indicated p110α mutants following growth in the presence of Dox (1 ug/mL) for 24 hours; β-actin, loading control. (B) Serum-dependency assays. Cells were cultured for 72 hours in medium containing Dox (1 μg/mL) with either normal FBS (10%) or low FBS (1%–2%) followed by crystal violet assays. Shown is the growth of cells cultured in the medium containing low FBS relative to the individual control of normal FBS (n = 6) followed by normalization to WT PIK3CA control. The dashed line represents the significance limit set as the value equal to WT PIK3CA. Mutants were classified as activating if they exhibited statistically enhanced cell growth in low serum compared with WT PIK3CA. Data are represented as box and whiskers. The whiskers go down to the minimum and up to the maximum value and plot each individual value as a point superimposed on the graph. The box extends from the 25th to 75th percentiles. The lines within the boxes represent the median value. *P < 0.05, **P < 0.01, ***P < 0.001, NS ≥ 0.05 for 1-tailed Student’s pairwise t test. The experiment was repeated 3 times with similar results. (C) Heatmap indicating the concordance of functionality conferred by HNSCC-associated noncanonical mutations tested in different cell line models. The mutations were assigned as “activating” if they exhibited an activity significantly higher than WT; otherwise, the mutations were annotated as “nonactivating.”