The Secretome Engages STAT3 to Favor a Cytokine-rich Microenvironment in Mediating Acquired Resistance to FGFR Inhibitors

18F-FDG PET as an imaging biomarker for the response to FGFR-targeted therapy of cancer cells via FGFR-initiated mTOR/HK2 axis

Rationale: The overall clinical response to FGFR inhibitor (FGFRi) is far from satisfactory in cancer patients stratified by FGFR aberration, the current biomarker in clinical practice. A novel biomarker to evaluate the therapeutic response to FGFRi in a non-invasive and dynamic manner is thus greatly desired. Methods: Six FGFR-aberrant cancer cell lines were used, including four FGFRi-sensitive ones (NCI-H1581, NCI-H716, RT112 and Hep3B) and two FGFRi-resistant ones (primary for NCI-H2444 and acquired for NCI-H1581/AR). Cell viability and tumor xenograft growth analyses were performed to evaluate FGFRi sensitivities, accompanied by corresponding ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake assay. mTOR/PLCγ/MEK-ERK signaling blockade by specific inhibitors or siRNAs was applied to determine the regulation mechanism. Results: FGFR inhibition decreased the in vitro accumulation of ¹⁸F-FDG only in four FGFRi-sensitive cell lines, but in neither of FGFRi-resistant ones. We then demonstrated that FGFRi-induced transcriptional downregulation of hexokinase 2 (HK2), a key factor of glucose metabolism and FDG trapping, via mTOR pathway leading to this decrease. Moreover, ¹⁸F-FDG PET imaging successfully differentiated the FGFRi-sensitive tumor xenografts from primary or acquired resistant ones by the tumor ¹⁸F-FDG accumulation change upon FGFRi treatment. Of note, both ¹⁸F-FDG tumor accumulation and HK2 expression could respond the administration/withdrawal of FGFRi in NCI-H1581 xenografts correspondingly. Conclusion: The novel association between the molecular mechanism (FGFR/mTOR/HK2 axis) and radiological phenotype (¹⁸F-FDG PET uptake) of FGFR-targeted therapy was demonstrated in multiple preclinical models. The adoption of ¹⁸F-FDG PET biomarker-based imaging strategy to assess response/resistance to FGFR inhibition may benefit treatment selection for cancer patients.

FGFR Inhibitors: Clinical Activity and Development in the Treatment of Cholangiocarcinoma

PURPOSE OF REVIEW

Cholangiocarcinoma is an aggressive cancer with a poor prognosis and limited treatment. Gene sequencing studies have identified genetic alterations in fibroblast growth factor receptor (FGFR) in a significant proportion of cholangiocarcinoma (CCA) patients. This review will discuss the FGFR signaling pathway's role in CCA and highlight the development of therapeutic strategies targeting this pathway.

RECENT FINDINGS

The development of highly potent and selective FGFR inhibitors has led to the approval of pemigatinib for FGFR2 fusion or rearranged CCA. Other selective FGFR inhibitors are currently under clinical investigation and show promising activity. Despite encouraging results, the emergence of resistance is inevitable. Studies using circulating tumor DNA and on-treatment tissue biopsies have elucidated underlying mechanisms of intrinsic and acquired resistance. There is a critical need to not only develop more effective compounds, but also innovative sequencing strategies and combinations to overcome resistance to selective FGFR inhibition. Therapeutic development of precision medicine for FGFR-altered CCA is a dynamic process of involving a comprehensive understanding of tumor biology, rational clinical trial design, and therapeutic optimization. Alterations in FGFR represent a valid therapeutic target in CCA and selective FGFR inhibitors are treatment options for this patient population.

Overcoming the senescence-associated secretory phenotype (SASP): a complex mechanism of resistance in the treatment of cancer

Senescence is a cellular state in which cells undergo persistent cell cycle arrest in response to nonlethal stress. In the treatment of cancer, senescence induction is a potent method of suppressing tumour cell proliferation. In spite of this, senescent cancer cells and adjacent nontransformed cells of the tumour microenvironment can remain metabolically active, resulting in paradoxical secretion of pro-inflammatory factors, collectively termed the senescence-associated secretory phenotype (SASP). The SASP plays a critical role in tumorigenesis, affecting numerous processes including invasion, metastasis, epithelial-to-mesenchymal transition (EMT) induction, therapy resistance and immunosuppression. With increasing evidence, it is becoming clear that cell type, tissue of origin and the primary cellular stressor are key determinants in how the SASP will influence tumour development and progression, including whether it will be pro- or antitumorigenic. In this review, we will focus on recent evidence regarding therapy-induced senescence (TIS) from anticancer agents, including chemotherapy, radiation, immunotherapy, and targeted therapies, and how each therapy can trigger the SASP, which in turn influences treatment efficacy. We will also discuss novel pharmacological manipulation of senescent cancer cells and the SASP, which offers an exciting and contemporary approach to cancer therapeutics. With future research, these adjuvant options may help to mitigate many of the negative side effects and protumorigenic roles that are currently associated with TIS in cancer.

Targeting the Fibroblast Growth Factor Receptor (FGFR) Family in Lung Cancer

Lung cancer is the most common cause of cancer-related deaths globally. Genetic alterations, such as amplifications, mutations and translocations in the fibroblast growth factor receptor (FGFR) family have been found in non-small cell lung cancer (NSCLC) where they have a role in cancer initiation and progression. FGFR aberrations have also been identified as key compensatory bypass mechanisms of resistance to targeted therapy against mutant epidermal growth factor receptor (EGFR) and mutant Kirsten rat sarcoma 2 viral oncogene homolog (KRAS) in lung cancer. Targeting FGFR is, therefore, of clinical relevance for this cancer type, and several selective and nonselective FGFR inhibitors have been developed in recent years. Despite promising preclinical data, clinical trials have largely shown low efficacy of these agents in lung cancer patients with FGFR alterations. Preclinical studies have highlighted the emergence of multiple intrinsic and acquired resistance mechanisms to FGFR tyrosine kinase inhibitors, which include on-target FGFR gatekeeper mutations and activation of bypass signalling pathways and alternative receptor tyrosine kinases. Here, we review the landscape of FGFR aberrations in lung cancer and the array of targeted therapies under clinical evaluation. We also discuss the current understanding of the mechanisms of resistance to FGFR-targeting compounds and therapeutic strategies to circumvent resistance. Finally, we highlight our perspectives on the development of new biomarkers for stratification and prediction of FGFR inhibitor response to enable personalisation of treatment in patients with lung cancer.

Pemigatinib, a potent inhibitor of FGFRs for the treatment of cholangiocarcinoma

The prognosis of patients affected by cholangiocarcinoma is classically poor. Until recently, chemotherapeutic drugs were the only systemic treatment option available, leading to an overall survival lower than 1 year. In recent decades, different genetic alterations have been identified as playing a key role in the oncogenic signaling. A subgroup of intrahepatic cholangiocarcinoma is characterized by FGFR family mutations, more frequently represented by gene fusions of FGFR2. Based on the results of FIGHT-202 trial, in April 2020 the US FDA approved the FGFR inhibitor pemigatinib in advanced previously treated cholangiocarcinoma patients with FGFR2 rearrangements, opening the way to targeted therapy in this disease. This review summarizes the body of evidence about the efficacy of pemigatinib in cholangiocarcinoma.

Modeling chemical effects on breast cancer: the importance of the microenvironment in vitro

Accumulating evidence suggests that our ability to predict chemical effects on breast cancer is limited by a lack of physiologically relevant in vitro models; the typical in vitro breast cancer model consists of the cancer cell and excludes the mammary microenvironment. As the effects of the microenvironment on cancer cell behavior becomes more understood, researchers have called for the integration of the microenvironment into in vitro chemical testing systems. However, given the complexity of the microenvironment and the variety of platforms to choose from, identifying the essential parameters to include in a chemical testing platform is challenging. This review discusses the need for more complex in vitro breast cancer models and outlines different approaches used to model breast cancer in vitro. We provide examples of the microenvironment modulating breast cancer cell responses to chemicals and discuss strategies to help pinpoint what components should be included in a model.

Novel activators and small-molecule inhibitors of STAT3 in cancer

Excessive activation of signal transducer and activator of transcription 3 (STAT3) signaling is observed in a subset of many cancers, making activated STAT3 a highly promising potential therapeutic target supported by multiple preclinical and clinical studies. However, early-phase clinical trials have produced mixed results with STAT3-targeted cancer therapies, revealing substantial complexity to targeting aberrant STAT3 signaling. This review discusses the diverse mechanisms of oncogenic activation of STAT3, and the small molecule inhibitors of STAT3 in cancer treatment.

Mechanisms of acquired resistance to fibroblast growth factor receptor targeted therapy

Oncogenic activation of the fibroblast growth factor receptor (FGFR) through mutations and fusions of the FGFR gene occur in a variety of different malignancies such as urothelial carcinoma and cholangiocarcinoma. Inhibition of the kinase domain of the FGFR with targeted oral FGFR inhibitors has been shown in both preclinical and early phase clinical trials to lead to meaningful reductions in tumour size and larger confirmatory randomized trials are underway. Acquired resistance to FGFR inhibition using a variety of mechanisms that includes, activation of alternate signaling pathways and expansion of tumour clones with gatekeeper mutations in the FGFR gene. This review summarizes the acquired resistance mechanisms to FGFR therapy and therapeutic approaches to circumventing resistance.

Preclinical evaluation of 3D185, a novel potent inhibitor of FGFR1/2/3 and CSF-1R, in FGFR-dependent and macrophage-dominant cancer models

Background

The interaction between tumor cells and their immunosuppressive microenvironment promotes tumor progression and drug resistance. Thus, simultaneously targeting tumor cells and stromal cells is expected to have synergistic antitumor effects. Herein, we present for the first time a preclinical antitumor investigation of 3D185, a novel dual inhibitor targeting FGFRs, which are oncogenic drivers, and CSF-1R, which is the major survival factor for protumor macrophages.

Methods

The antitumor characteristics of 3D185 were assessed by a range of assays, including kinase profiling, cell viability, cell migration, immunoblotting, CD8⁺ T cell suppression, and in vivo antitumor efficacy, followed by flow cytometric and immunohistochemical analyses of tumor-infiltrating immune cells and endothelial cells in nude mice and immune-competent mice.

Results

3D185 significantly inhibited the kinase activity of FGFR1/2/3 and CSF-1R, with equal potency and high selectivity over other kinases. 3D185 suppressed FGFR signaling and tumor cell growth in FGFR-driven models both in vitro and in vivo. In addition, 3D185 could inhibit the survival and M2-like polarization of macrophages, reversing the immunosuppressive effect of macrophages on CD8⁺ T cells as well as CSF1-differentiated macrophage induced-FGFR3-aberrant cancer cell migration. Furthermore, 3D185 inhibited tumor growth via remodeling the tumor microenvironment in TAM-dominated tumor models.

Conclusions

3D185 is a promising antitumor candidate drug that simultaneously targets tumor cells and their immunosuppressive microenvironment and has therapeutic potential due to synergistic effects. Our study provides a solid foundation for the investigation of 3D185 in cancer patients, particularly in patients with aberrant FGFR and abundant macrophages, who respond poorly to classic pan-FGFRi treatment.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1357-y) contains supplementary material, which is available to authorized users.