Article Text

Download PDFPDF

230 Single cell PIK3 gene expression patterns support duvelisib (PI3K-delta, gamma inhibitor) treatment of melanoma and other tumors after checkpoint inhibitor therapy
  1. Samantha Hidy and
  2. David Weaver
  1. Verastem Oncology, Needham, MA, USA


Background Duvelisib, an FDA-approved oral phosphoinositide 3-kinase (PI3K)-δ,γ inhibitor, targets tumor cells of B/T cell malignancies, but may modulate non-malignant immune cells in the tumor microenvironment (TME) of many cancers. PI3K–δ and PI3K–γ downmodulate immunosuppressive Tregs and myeloid cells in solid tumors.1–3 We used single-cell RNA analysis of PIK3CD and PIK3CG to explore resistance mechanisms to checkpoint inhibitors (CPI).

Methods Single-cell melanoma (SKCM) RNAseq datasets: GSE120575;4 CD45+ cells from 48 CPI responders and non-responder tumors, and GSE115978;5 33 treatment-naïve and CPI-progressing (resistant) tumors. Cancer cells and CD45+ TME subpopulations, specified by gene expression signatures and tSNE plots, had PI3K gene expressions profiled. Differential gene expression (DE) was gated in MAST/Seurat. Fishers test Odds Ratio (OR) was calculated for ‘high’ expression.

Results PIK3CD expression is higher in SKCM than most cancers (10.8 median RSEM log 2).7 By single-cell analysis, PIK3CD (> 0.3 log2 TPM) occurs in 68.2% of cancer cells, with PIK3CB, PIK3CA, and PIK3CG expressed in 32.3%, 12.0%, and 7.2% respectively. PIK3CD-high cancer cells (>4 log2 TPM) have a 711-gene DE gene signature mostly related to immune processes. A higher proportion of cancer cells in CPI resistant tumors express PIK3CD, than untreated tumors (OR 2.02, 95% CI 1.65–2.48, p=3.04 × 10–12), as do PIK3CD+PIK3CG-expressing cancer cells (OR 2.14, 95% CI 1.47–3.13, p=4.2 × 10-5). Additionally, in PI3K–δ or PI3K–γ high melanoma cell lines duvelisib inhibited proliferation, p-AKT and c-myc.7 PIK3CD and PIK3CG are prominently expressed in many SKCM CD45+ TME cells (84.5% and 31.7% CD45+ respectively). PIK3CD (>0.3 log2 TPM) occurs in a high fraction of T (85.7%), CD8+ T (86.3%), CD4+ T (86.9%), B (78.5%), macrophages (88%), and NK (85%). PIK3CG is highest in B, dendritic, cycling lymphocytes and plasma cells. Strikingly, a significantly higher proportion of PIK3CD+ cells occur in resistant tumors compared to untreated for all CD45+ cells, (OR 1.64, 95% CI 1.40–1.94, p=4.79 × 10-10), CD8+ T (OR 2.15, 95% CI 1.61–2.86, p=6.5 × 10-8), and an exhausted C8+ T subpopulation (OR 3.17, 95% CI 1.89–5.37, p=2.95 × 10-6). PIK3CD+PIK3CG-expressing CD45+ cells are significantly increased in CPI-resistant tumors (OR 1.22, 95% CI 1.07–1.39, p=0.002).

Conclusions These findings support a mechanism where CPI therapies may contribute to modulation of PI3Kδ expression in cancer cells and the immune TME. The PI3K-δ,γ inhibitor duvelisib is being investigated in combination with CPI and evaluated in the context of CPI resistance in clinical trials: pembrolizumab (HNSC, NCT04193293), and nivolumab (Richter’s Syndrome, NCT03892044).


  1. Ali K, Soond DR, Pineiro R, Hagemann T, Pearce W, Lim EL, Bouabe H, Scudamore CL, Hancox T, Maecker H, Friedman L, Turner M, Okkenhaug K, Vanhaesebroeck B. Inactivation of PI(3)K p110δ breaks regulatory T-cell-mediated immune tolerance to cancer Nature 2014; 510(7505):407–411.

  2. Kaneda MM, Messer KS, Ralainirina N, Li H, Leem CJ, Gorjestani S, Woo G, Nguyen AV, Figueiredo CC, Foubert P, Schmid MC, Pink M, Winkler DG, Rausch M, Palombella VJ, Kutok J, McGovern K, Frazer KA, Wu X, Karin M, Sasik R, Cohen EE, Varner JA. PI3Kγ is a molecular switch that controls immune suppression. Nature 2016; 539(7629):437–442.

  3. De Henau O, Rausch M, Winkler D, Campesato LF, Liu C, Cymerman DH, Budhu S, Ghosh A, Pink M, Tchaicha J, Douglas M, Tibbitts T, Sharma S, Proctor J, Kosmider N, White K, Stern H, Soglia J, Adams J, Palombella VJ, McGovern K, Kutok JL, Wolchok JD, Merghoub T. Overcoming resistance to checkpoint blockade therapy by targeting PI3Kγ in myeloid cells. Nature 2016; 539(7629):443–447.

  4. Sade-Feldman M, Yizhak K, Bjorgaard SL, Ray JP, de Boer CG, Jenkins RW, Lieb DJ, Chen JH, Frederick DT, Barzily-Rokni M, Freeman SS, Reuben A, Hoover PJ, Villani AC, Ivanova E, Portell A, Lizotte PH, Aref AR, Eliane JP, Hammond MR, Vitzthum H, Blackmon SM, Li B, Gopalakrishnan V, Reddy SM, Cooper ZA, Paweletz CP, Barbie DA, Stemmer-Rachamimov A, Flaherty KT, Wargo JA, Boland GM, Sullivan RJ, Getz G, Hacohen N. Defining T Cell States Associated with Response to Checkpoint Immunotherapy in Melanoma. Cell 2018; 175: 998–1013.

  5. Jerby-Arnon L, Shah P, Cuoco MS, Rodman C, Su MJ, Melms JC, Leeson R, Kanodia A, Mei S, Lin JR, Wang S, Rabasha B, Liu D, Zhang G, Margolais C, Ashenberg O, Ott PA, Buchbinder EI, Haq R, Hodi FS, Boland GM, Sullivan RJ, Frederick DT, Miao B, Moll T, Flaherty KT, Herlyn M, Jenkins RW, Thummalapalli R, Kowalczyk MS, Cañadas I, Schilling B, Cartwright ANR, Luoma AM, Malu S2, Hwu P, Bernatchez C, Forget MA, Barbie DA, Shalek AK, Tirosh I, Sorger PK, Wucherpfennig K, Van Allen EM, Schadendorf D, Johnson BE, Rotem A, Rozenblatt-Rosen O, Garraway LA, Yoon CH, Izar B, Regev A. A Cancer Cell Program Promotes T Cell Exclusion and Resistance to Checkpoint Blockade. Cell 2018; 175: 984–997.

  6. Firebrowse Gene Expression Viewer

  7. Coma S, Weaver DT, Pachter JA. [Poster #663] The dual PI3K-δ/PI3K-γ inhibitor duvelisib inhibits signaling and proliferation of solid tumor cells expressing PI3K-δ and/or PI3K-γ. AACR. 2020.

This is an open access article distributed in accordance with the Creative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits others to copy, redistribute, remix, transform and build upon this work for any purpose, provided the original work is properly cited, a link to the licence is given, and indication of whether changes were made. See:

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.