Colorectal cancers (CRCs) that are sensitive to the anti-epidermal growth factor receptor (EGFR) antibodies cetuximab or panitumumab almost always develop resistance within several months of ...initiating therapy. We report the emergence of polyclonal KRAS, NRAS, and BRAF mutations in CRC cells with acquired resistance to EGFR blockade. Regardless of the genetic alterations, resistant cells consistently displayed mitogen-activated protein kinase kinase (MEK) and extracellular signal-regulated kinase (ERK) activation, which persisted after EGFR blockade. Inhibition of MEK1/2 alone failed to impair the growth of resistant cells in vitro and in vivo. An RNA interference screen demonstrated that suppression of EGFR, together with silencing of MEK1/2, was required to hamper the proliferation of resistant cells. Indeed, concomitant pharmacological blockade of MEK and EGFR induced prolonged ERK inhibition and severely impaired the growth of resistant tumor cells. Heterogeneous and concomitant mutations in KRAS and NRAS were also detected in plasma samples from patients who developed resistance to anti-EGFR antibodies. A mouse xenotransplant from a CRC patient who responded and subsequently relapsed upon EGFR therapy showed exquisite sensitivity to combinatorial treatment with MEK and EGFR inhibitors. Collectively, these results identify genetically distinct mechanisms that mediate secondary resistance to anti-EGFR therapies, all of which reactivate ERK signaling. These observations provide a rational strategy to overcome the multifaceted clonal heterogeneity that emerges when tumors are treated with targeted agents. We propose that MEK inhibitors, in combination with cetuximab or panitumumab, should be tested in CRC patients who become refractory to anti-EGFR therapies.
Small cell lung cancer (SCLC) has a 5-year survival rate of <7%. Rapid emergence of acquired resistance to standard platinum-etoposide chemotherapy is common and improved therapies are required for ...this recalcitrant tumour. We exploit six paired pre-treatment and post-chemotherapy circulating tumour cell patient-derived explant (CDX) models from donors with extensive stage SCLC to investigate changes at disease progression after chemotherapy. Soluble guanylate cyclase (sGC) is recurrently upregulated in post-chemotherapy progression CDX models, which correlates with acquired chemoresistance. Expression and activation of sGC is regulated by Notch and nitric oxide (NO) signalling with downstream activation of protein kinase G. Genetic targeting of sGC or pharmacological inhibition of NO synthase re-sensitizes a chemoresistant CDX progression model in vivo, revealing this pathway as a mediator of chemoresistance and potential vulnerability of relapsed SCLC.
Molecular targeted drugs are clinically effective anti-cancer therapies. However, tumours treated with single agents usually develop resistance. Here we use colorectal cancer (CRC) as a model to ...study how the acquisition of resistance to EGFR-targeted therapies can be restrained. Pathway-oriented genetic screens reveal that CRC cells escape from EGFR blockade by downstream activation of RAS-MEK signalling. Following treatment of CRC cells with anti-EGFR, anti-MEK or the combination of the two drugs, we find that EGFR blockade alone triggers acquired resistance in weeks, while combinatorial treatment does not induce resistance. In patient-derived xenografts, EGFR-MEK combination prevents the development of resistance. We employ mathematical modelling to provide a quantitative understanding of the dynamics of response and resistance to these single and combination therapies. Mechanistically, we find that the EGFR-MEK Combo blockade triggers Bcl-2 and Mcl-1 downregulation and initiates apoptosis. These results provide the rationale for clinical trials aimed at preventing rather than intercepting resistance.
Introduced in 1987, platinum-based chemotherapy remains standard of care for small cell lung cancer (SCLC), a most aggressive, recalcitrant tumor. Prominent barriers to progress are paucity of tumor ...tissue to identify drug targets and patient-relevant models to interrogate novel therapies. Following our development of circulating tumor cell patient-derived explants (CDX) as models that faithfully mirror patient disease, here we exploit CDX to examine new therapeutic options for SCLC.
We investigated the efficacy of the PARP inhibitor olaparib alone or in combination with the WEE1 kinase inhibitor AZD1775 in 10 phenotypically distinct SCLC CDX
and/or
These CDX represent chemosensitive and chemorefractory disease including the first reported paired CDX generated longitudinally before treatment and upon disease progression.
There was a heterogeneous depth and duration of response to olaparib/AZD1775 that diminished when tested at disease progression. However, efficacy of this combination consistently exceeded that of cisplatin/etoposide, with cures in one CDX model. Genomic and protein analyses revealed defects in homologous recombination repair genes and oncogenes that induce replication stress (such as MYC family members), predisposed CDX to combined olaparib/AZD1775 sensitivity, although universal predictors of response were not noted.
These preclinical data provide a strong rationale to trial this combination in the clinic informed by prevalent, readily accessed circulating tumor cell-based biomarkers. New therapies will be evaluated in SCLC patients after first-line chemotherapy, and our data suggest that the combination of olaparib/AZD1775 should be used as early as possible and before disease relapse.
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Targeting DNA damage in SCLC Foy, Victoria; Schenk, Maximilian W.; Baker, Katie ...
Lung cancer (Amsterdam, Netherlands),
December 2017, 2017-12-00, Letnik:
114
Journal Article
Recenzirano
Odprti dostop
•SCLC is characterised by high proliferation and rapid development of chemo resistant disease.•SCLC is reliant on functional DNA damage repair pathways and cell cycle checkpoints to ...flourish.•Recently there has been improved understanding of strategies to exploit DNA repair mechanisms’ for therapeutic benefit.
SCLC accounts for 15% of lung cancer worldwide. Characterised by early dissemination and rapid development of chemo-resistant disease, less than 5% of patients survive 5 years. Despite 3 decades of clinical trials there has been no change to the standard platinum and etoposide regimen for first line treatment developed in the 1970’s.
The exceptionally high number of genomic aberrations observed in SCLC combined with the characteristic rapid cellular proliferation results in accumulation of DNA damage and genomic instability. To flourish in this precarious genomic context, SCLC cells are reliant on functional DNA damage repair pathways and cell cycle checkpoints.
Current cytotoxic drugs and radiotherapy treatments for SCLC have long been known to act by induction of DNA damage and the response of cancer cells to such damage determines treatment efficacy. Recent years have witnessed improved understanding of strategies to exploit DNA damage and repair mechanisms in order to increase treatment efficacy.
This review will summarise the rationale to target DNA damage response in SCLC, the progress made in evaluating novel DDR inhibitors and highlight various ongoing challenges for their clinical development in this disease.
Lung cancers are the main cause of cancer-related deaths worldwide. Efforts placed to improve the survival of lung cancer patients and untangle the complexity of this disease, have resulted in the ...generation of hundreds of lung cancer cell lines and several genetically engineered mouse models (GEMMs). Although these research tools have extended our knowledge of lung cancer, improvement in the clinical care of lung cancer patients have been limited overall, with measured optimism regarding initial responses to targeted therapies in stratified subgroups of patients. Patient-derived xenograft (PDX) models are beginning to assist ‘personalized therapy’ approaches particularly in non-small cell lung cancer (NSCLC) however biopsies of lung cancers to generate PDXs are not without challenges and risks to the patient. Liquid biopsies, on the other hand, are a rapid and non-invasive procedure allowing the collection of circulating tumor cells (CTCs) with a single 10 mL blood draw. These CTCs recapitulate the molecular heterogeneity of the corresponding tumors and, therefore, can be used as surrogates to study tumor biology and generate new patient-derived models. Here, we discuss the CTC-derived models that have been generated, most notably in small cell lung cancer (SCLC), highlighting challenges and opportunities related to these novel preclinical tools.
Background and Purpose
Small cell lung cancer (SCLC) is an aggressive disease with median survival of <2 years. Tumour biopsies for research are scarce, especially from extensive‐stage patients, with ...repeat sampling at disease progression rarely performed. We overcame this limitation for relevant preclinical models by developing SCLC circulating tumour cell derived explants (CDX), which mimic the donor tumour pathology and chemotherapy response. To facilitate compound screening and identification of clinically relevant biomarkers, we developed short‐term ex vivo cultures of CDX tumour cells.
Experimental Approach
CDX tumours were disaggregated, and the human tumour cells derived were cultured for a maximum of 5 weeks. Phenotypic, transcriptomic and pharmacological characterization of these cells was performed.
Key Results
CDX cultures maintained a neuroendocrine phenotype, and most changes in the expression of protein‐coding genes observed in cultures, for up to 4 weeks, were reversible when the cells were re‐implanted in vivo. Moreover, the CDX cultures exhibited a similar sensitivity to chemotherapy compared to the corresponding CDX tumour in vivo and were able to predict in vivo responses to therapeutic candidates.
Conclusions and Implications
Short‐term cultures of CDX provide a tractable platform to screen new treatments, identify predictive and pharmacodynamic biomarkers and investigate mechanisms of resistance to better understand the progression of this recalcitrant tumour.
Small cell lung cancer (SCLC) has been defined as a "recalcitrant" disease and better treatments are urgently needed. High mutational burden, oncogene induced replication stress and universal loss of ...G1 checkpoints in SCLC validate it for treatment with DNA damage response inhibitors (DDRi). I investigated the effects of the PARP inhibitor olaparib and the WEE1 inhibitor AZD1775 on SCLC preclinical models. PARP is a crucial regulator of several DNA damage pathways, whilst WEE1 controls CDK activity and cell cycle progression. Their dual inhibition has emerged as a promising strategy to drive SCLC cells beyond their survival threshold.In this thesis, I present data that supports the exploitation of circulating tumour cell patient-derived explant models (CDX) as a platform to study the response of SCLC patients to several DDRi and to identify biomarkers of treatment response. I demonstrated that CDX-derived cells can be cultured successfully ex vivo, and retain most of the features of the donor CDX tumour. In particular, the majority of CDX cultures I derived were able to predict the original CDX's in vivoresponse to therapies.I utilised the CDX culture platform to investigate the potential of combining AZD1775 and olaparib. Screening of a panel of 20 CDX cultures demonstrated disparate responses, highlighting the need for predictive biomarkers of response to stratify patients in clinical trials. However, the investigation of cell cycle checkpoints and DNA damage repair pathways revealed a high degree of heterogeneity between individual CDX models. This challenged the identification of a universal response biomarker, and highlighted the need for a better understanding of the molecular mechanisms underpinning these treatment responses.Ex vivoscreens of different DDRi combinations identified a group of CDX resistant to most combinations tested. These models have an intrinsic ability to survive despite the induction of substantial DNA damage. AZD2811, an inhibitor of the mitotic regulator Aurora kinase B, was highly cytotoxic in some of the otherwise resistant cultures, making this drug a promising alternative treatment for chemorefractory SCLC patients. Overall, this thesis shows that CDX cultures are a faithful model to study SCLC and confirms DDRi as a promising therapeutic strategy for SCLC patients.
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