Leonard Girnita's Group

Cross-talk between the receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCRs). Functional, diagnostic and therapeutic implications for cancer.

General description: "Receptor pathology" lab, performing translational research by investigating the molecular properties and regulatory mechanisms that control the function of plasma membrane receptors under normal and pathological circumstances. The final goal is to determine potential utility of the signalling complexes involved in the RTKs/GPCRs cross talk as biomarkers or molecular targets in cancer.

Hypothesis underlying research: Signalling complexes coordinated by beta-arrestins, kinases and (de)ubiqitine ligases contribute to tumourigenesis and the progression of cancer and could be targeted in therapies.

Our hypothesis and aims

Cross-talk at multiple levels between G protein-coupled receptor and growth factor receptor pathways has a fundamental role in coordinating downstream signaling molecules and this ultimately controls development and maintenance of the malignant phenotype.

The objective of this program is to investigate the function of the signaling complexes involved in the GPCR/RTK cross-talk and determine their potential utility as potential biomarkers or therapeutic targets in cancer. Our main focus is on the signaling complexes coordinated by β-arrestins and involving kinases, ubiquitin ligases and deubiquitinating enzymes, which we hypothesize to contribute to tumourigenesis and the progression of cancer and could be targeted in therapies.


Cancer is today one of the most important public health problems in Europe: there are 3.2 million new cases and 1.7 million deaths each year. With the ageing of the European population these numbers are predicted to steadily increase. Therefore research must focus on disease etiology, new medicines and therapies as well as on identification and validation of drug targets and biomarkers that aid in the prevention, early diagnosis and more tailored treatment.

In the selection leading to cancer, cancer cells make use of the normal extracellular signaling for proliferation, migration and/or antiapoptosis to gain a growth advantage over normal cells. These signals are, in part, generated by plasma membrane receptors. Our work refers to two major classes: G proteincoupled receptors (GPCR) and growth factor receptors (receptor tyrosine kinases, RTKs).

The G protein-coupled receptors (GPCRs) represent the largest (>1000) family of plasma membrane receptors and they mediate a large proportion of physiological functions. Moreover, GPCRs represent the most prominent family of validated pharmacological targets in current medical practice accounting for about 50% of all prescription drug sales worldwide. However, the involvement of GPCRs in cancer is unappreciated and their potential as therapeutic targets is scarcely exploited.

Three families of proteins coordinate the function of the GPCR: the heterotrimeric G proteins, the G proteincoupled receptor kinases (GRKs), and the β-arrestins.

The tyrosine kinase receptors (RTKs) are a related family of cell surface receptors with similar structure and functions. Although few compared with the large number of GPCR, RTKs receive particular interest for targeted therapy in cancer. Among them, IGF-1R is considered as one of the most attractive target for cancer therapy. In vivo and in vitro studies using IGF-1R antibodies, small molecule inhibitors and antisense technology have shown that IGF-1R is functionally essential for tumor cell growth and cancer cell proliferation in most if not all forms of cancer. Yet, the lessons from the clinical trials using IGF-1R antibodies indicates that tumors initially addicted to IGF-1R signaling develop rapid resistance to the therapy. To address this dilemma, it is crucial to identify the subset of patients likely to respond. Biomarkers that predict as well as tools that would enhance response to IGF-1R therapy are urgently needed.

Research line 1

Investigating the molecular mechanism of beta-arrestin/GRK-biased agonism at the IGF-1R

During the last years our lab demonstrated that β-arrestin and GRKs, proteins traditionally associated with GPCR functions, also control the IGF-1R (and possibly other RTKs) expression and signaling. In this project we aim to functionally characterize the GRKs/β-arrestin roles in controlling RTK signaling as well as their functional implications for cancer development.

Research line 2

Evaluating the beta-arrestin signaling complex as a potential diagnostic or prognostic biomarker.

β-arrestin regulates formation of a scaffolding protein that integrates IGF-1R (RTK) and GPCR signaling as well as Raf and Ras downstream signaling. Ras/Raf genes are mutated in several cancer types including melanoma, colon and pancreatic cancer. Our data indicates that the composition of the β-arrestin complex may be different in malignant cells and normal cells. Therefore, we predict that the status of the β-arrestin complex may differentiate non-transformed cells from tumour cells, and a migratory phenotype from a non-migratory phenotype.

Research line 3

GRKs/beta-arrestins as targets for receptor cross talk in cancer

Since β-arrestin plays a critical role in modulating signaling pathways emanating from many GPCR and RTKs, alterations in β-arrestin function, induced by various forms of receptor cross talk, are likely to have pronounced effects on intracellular signaling. In this project we will investigate the biological effects as well as therapeutic values of following various perturbations of β-arrestin/GRK functions.

Simultaneously we are also investigating a novel approach for cancer treatment: biasing RTK signaling through GPCR.


Dawei Song
Old receptors learn new tricks : biasing anti-IGF1R cancer therapy through the GPCR system
February 25, 2022

Caitrin Crudden
Biased signalling at the IGF-1R: pitfalls and potential of the GRK/β-arrestin system in cancer therapeutics
June 15, 2018

Naida Suleymanova
Beta-arrestins in cancer: linking pro-tumorigenic extracellular activated signaling with the tumor suppressor p53 pathway
August 25, 2017

Huiyuan Zheng
Molecular function and targeting of beta-arrestins in cancer.
September 14, 2012

Natalia Natalishvili
IGF-1R: Studies on the expression and role in transformation
May 29, 2009

Linda Rosengren
Targeting the GH/IGF-1 axis with novel, small molcule inhibitors
October 26, 2007

Bita Sehat
SUMO and ubiquitin: the Yin and Yang of IGF-1R function
October 25, 2007

Mario A Economou
Uveal melanoma and macular degeneration: Molecular biology and potential therapeutic applications
September 7, 2007

Radu Vasilcanu
Regulation of insulin-like growth factor-1 receptor expression and signaling
June 15, 2007

Daiana Vasilcanu
IGF-1R inhibition: A tool for functional studies of insulin-like growth factor family in malignant cells
February 3, 2006

Research funding

  • Karolinska Institutet funds
  • The Swedish Cancer Society
  • The Swedish Research Council
  • The Swedish Childhood Cancer Foundation
  • Crown Princess Margareta's Foundation for the Visually Impaired
  • Welander-Finsen Foundation
  • King Gustav V Jubilee Foundation
  • Vinnova
  • Stockholm County

Group members

Leonard Girnita, MD, PhD, Associate Professor, Group leader
Ada Girnita, MD, PhD, Senior researcher, project leader
Takashi Shibano, PhD, Postdoc
Dawei Song, MD, PhD, Postdoc
Sonia Oana Cismas, MD, PhD student
Iara Rocha Trocoli Drakensjö, MD, PhD student
Eric Trocmé, MD, PhD student
Simin Zhang, MD, PhD student
Xiaohao Wang, MD, PhD student
Caitrin Crudden, PhD
Sylvya Pasca, PhD student
Diana Florescu, MD, PhD student


Mireia Cruz De los Santos, undergraduate student
Naida Suleymanova, PhD student
Claire Worrall, MD, PhD, Postdoc
Iulian Oprea, MD, PhD, Postdoc
Beklem Bostancioglu, PhD, Postdoc
Daiana Vasilcanu, MD, PhD, Researcher
Julianna Serly, PhD, Postdoc
Tingting Ling, MD, PhD, Postdoc
Elfar Ulfarsson, MD, PhD student
Eugenio Triay, MD, PhD student
Huiyuan Zheng, PhD student
Natalia Natalishvili, MD, PhD student
Chen Qiu, MD, visiting PhD student
Dan Stefanescu, MD, visiting PhD student
Daniela Nedelcu, visiting PhD student
Tiehong Zhang, visiting PhD student

Selected publications

IGF-1R is a molecular determinant for response to p53 reactivation therapy in conjunctival melanoma.
Song D, Cismas S, Crudden C, Trocme E, Worrall C, Suleymanova N, Lin T, Zheng H, Seregard S, Girnita A, Girnita L
Oncogene 2022 01;41(4):600-611

Inhibition of G protein-coupled receptor kinase 2 promotes unbiased downregulation of IGF-1 receptor and restrains malignant cell growth.
Crudden C, Shibano T, Song D, Dragomir MP, Cismas S, Serly J, et al
Cancer Res 2020 Nov;():

The Long Noncoding RNA CCAT2 induces chromosomal instability through BOP1 - AURKB signaling.
Chen B, Dragomir MP, Fabris L, Bayraktar R, Knutsen E, Liu X, et al
Gastroenterology 2020 Aug;():

Decrypting noncoding RNA interactions, structures, and functional networks.
Fabbri M, Girnita L, Varani G, Calin GA
Genome Res 2019 09;29(9):1377-1388

Cancer-associated rs6983267 SNP and its accompanying long noncoding RNA CCAT2 induce myeloid malignancies via unique SNP-specific RNA mutations.
Shah MY, Ferracin M, Pileczki V, Chen B, Redis R, Fabris L, et al
Genome Res 2018 04;28(4):432-447

Functional antagonism of β-arrestin isoforms balance IGF-1R expression and signalling with distinct cancer-related biological outcomes.
Suleymanova N, Crudden C, Shibano T, Worrall C, Oprea I, Tica A, et al
Oncogene 2017 10;36(41):5734-5744

Unbalancing p53/Mdm2/IGF-1R axis by Mdm2 activation restrains the IGF-1-dependent invasive phenotype of skin melanoma.
Worrall C, Suleymanova N, Crudden C, Trocoli Drakensjö I, Candrea E, Nedelcu D, et al
Oncogene 2017 06;36(23):3274-3286

β-Arrestin-biased agonism as the central mechanism of action for insulin-like growth factor 1 receptor-targeting antibodies in Ewing's sarcoma.
Zheng H, Shen H, Oprea I, Worrall C, Stefanescu R, Girnita A, et al
Proc Natl Acad Sci U S A 2012 Dec;109(50):20620-5

Selective recruitment of G protein-coupled receptor kinases (GRKs) controls signaling of the insulin-like growth factor 1 receptor.
Zheng H, Worrall C, Shen H, Issad T, Seregard S, Girnita A, et al
Proc Natl Acad Sci U S A 2012 May;109(18):7055-60

Identification of the cathelicidin peptide LL-37 as agonist for the type I insulin-like growth factor receptor.
Girnita A, Zheng H, Grönberg A, Girnita L, Ståhle M
Oncogene 2012 Jan;31(3):352-65

Targeting the insulin-like growth factor-1 receptor by picropodophyllin as a treatment option for glioblastoma.
Yin S, Girnita A, Strömberg T, Khan Z, Andersson S, Zheng H, et al
Neuro Oncol 2010 Jan;12(1):19-27

Malignant solitary fibrous tumour of the orbit.
Girnita L, Sahlin S, Orrego A, Seregard S
Acta Ophthalmol 2009 Jun;87(4):464-7

Aberrant intracellular IGF-1R beta-subunit makes receptor knockout cells (IGF1R-/-) susceptible to oncogenic transformation.
Natalishvili N, Axelson M, Girnita L, Larsson O, Vasilcanu D
Exp Cell Res 2009 May;315(8):1458-67

New picropodophyllin analogs via palladium-catalyzed allylic alkylation-Hiyama cross-coupling sequences.
Vitale M, Prestat G, Lopes D, Madec D, Kammerer C, Poli G, et al
J Org Chem 2008 Aug;73(15):5795-805

Identification of c-Cbl as a new ligase for insulin-like growth factor-I receptor with distinct roles from Mdm2 in receptor ubiquitination and endocytosis.
Sehat B, Andersson S, Girnita L, Larsson O
Cancer Res 2008 Jul;68(14):5669-77

Picropodophyllin induces downregulation of the insulin-like growth factor 1 receptor: potential mechanistic involvement of Mdm2 and beta-arrestin1.
Vasilcanu R, Vasilcanu D, Rosengren L, Natalishvili N, Sehat B, Yin S, et al
Oncogene 2008 Mar;27(11):1629-38

Insulin-like growth factor type-I receptor-dependent phosphorylation of extracellular signal-regulated kinase 1/2 but not Akt (protein kinase B) can be induced by picropodophyllin.
Vasilcanu R, Vasilcanu D, Sehat B, Yin S, Girnita A, Axelson M, et al
Mol Pharmacol 2008 Mar;73(3):930-9

Beta-arrestin and Mdm2 mediate IGF-1 receptor-stimulated ERK activation and cell cycle progression.
Girnita L, Shenoy SK, Sehat B, Vasilcanu R, Vasilcanu D, Girnita A, et al
J Biol Chem 2007 Apr;282(15):11329-38

The insulin-like growth factor-1 receptor inhibitor PPP produces only very limited resistance in tumor cells exposed to long-term selection.
Vasilcanu D, Weng WH, Girnita A, Lui WO, Vasilcanu R, Axelson M, et al
Oncogene 2006 May;25(22):3186-95

The insulin-like growth factor-I receptor inhibitor picropodophyllin causes tumor regression and attenuates mechanisms involved in invasion of uveal melanoma cells.
Girnita A, All-Ericsson C, Economou MA, Aström K, Axelson M, Seregard S, et al
Clin Cancer Res 2006 Feb;12(4):1383-91

IGF-1 receptor tyrosine kinase inhibition by the cyclolignan PPP induces G2/M-phase accumulation and apoptosis in multiple myeloma cells.
Strömberg T, Ekman S, Girnita L, Dimberg LY, Larsson O, Axelson M, et al
Blood 2006 Jan;107(2):669-78

Inhibiting the IGF-1 receptor tyrosine kinase with the cyclolignan PPP: an in vitro and in vivo study in the 5T33MM mouse model.
Menu E, Jernberg-Wiklund H, Stromberg T, De Raeve H, Girnita L, Larsson O, et al
Blood 2006 Jan;107(2):655-60

{beta}-Arrestin is crucial for ubiquitination and down-regulation of the insulin-like growth factor-1 receptor by acting as adaptor for the MDM2 E3 ligase.
Girnita L, Shenoy SK, Sehat B, Vasilcanu R, Girnita A, Lefkowitz RJ, et al
J Biol Chem 2005 Jul;280(26):24412-9

Expression and growth dependency of the insulin-like growth factor I receptor in craniopharyngioma cells: a novel therapeutic approach.
Ulfarsson E, Karström A, Yin S, Girnita A, Vasilcanu D, Thoren M, et al
Clin Cancer Res 2005 Jul;11(13):4674-80

Cyclolignans as inhibitors of the insulin-like growth factor-1 receptor and malignant cell growth.
Girnita A, Girnita L, del Prete F, Bartolazzi A, Larsson O, Axelson M
Cancer Res 2004 Jan;64(1):236-42

Mdm2-dependent ubiquitination and degradation of the insulin-like growth factor 1 receptor.
Girnita L, Girnita A, Larsson O
Proc Natl Acad Sci U S A 2003 Jul;100(14):8247-52

Increased expression of insulin-like growth factor I receptor in malignant cells expressing aberrant p53: functional impact.
Girnita L, Girnita A, Brodin B, Xie Y, Nilsson G, Dricu A, et al
Cancer Res 2000 Sep;60(18):5278-83

A link between basic fibroblast growth factor (bFGF) and EWS/FLI-1 in Ewing's sarcoma cells.
Girnita L, Girnita A, Wang M, Meis-Kindblom JM, Kindblom LG, Larsson O
Oncogene 2000 Aug;19(37):4298-301

Selected reviews and book chapters

The tale of a tail: The secret behind IGF-1R's oncogenic power.
Crudden C, Girnita L
Sci Signal 2020 May;13(633):

Non-Coding RNAs in IGF-1R Signaling Regulation: The Underlying Pathophysiological Link between Diabetes and Cancer.
Chen B, Li J, Chi D, Sahnoune I, Calin S, Girnita L, et al
Cells 2019 12;8(12):

Below the Surface: IGF-1R Therapeutic Targeting and Its Endocytic Journey.
Crudden C, Song D, Cismas S, Trocmé E, Pasca S, Calin GA, et al
Cells 2019 10;8(10):

Blurring Boundaries: Receptor Tyrosine Kinases as functional G Protein-Coupled Receptors.
Crudden C, Shibano T, Song D, Suleymanova N, Girnita A, Girnita L
Int Rev Cell Mol Biol 2018 ;339():1-40

Chapter Seven - When Phosphorylation Encounters Ubiquitination: A Balanced Perspective on IGF-1R Signaling.
Girnita L, Takahashi SI, Crudden C, Fukushima T, Worrall C, Furuta H, et al
Prog Mol Biol Transl Sci 2016 ;141():277-311

Non-coding RNAs: the cancer genome dark matter that matters!
Ling H, Girnita L, Buda O, Calin GA
Clin Chem Lab Med 2017 May;55(5):705-714

Differential regulation of IGF-1 and Insulin signaling by GRKs
Girnita L, Girnita A and Crudden C
Book chapter in:  Gurevich  and J. Tesmer(eds.), G Protein-Coupled Receptor Kinases, Advances in Biochemistry in Health and Disease.

Targeting the IGF-1R: The Tale of the Tortoise and the Hare.
Crudden C, Girnita A, Girnita L
Front Endocrinol (Lausanne) 2015 ;6():64

The dichotomy of the Insulin-like growth factor 1 receptor: RTK and GPCR: friend or foe for cancer treatment?
Crudden C, Ilic M, Suleymanova N, Worrall C, Girnita A, Girnita L
Growth Horm IGF Res 2015 Feb;25(1):2-12

Something old, something new and something borrowed: emerging paradigm of insulin-like growth factor type 1 receptor (IGF-1R) signaling regulation.
Girnita L, Worrall C, Takahashi S, Seregard S, Girnita A
Cell Mol Life Sci 2014 Jul;71(13):2403-27