Killing of Kras-Mutant Colon Cancer Cells via Rac-Independent Actin Remodeling by the GBP Cytokine, a Physiological PI3K Inhibitor Therapeutically Effective In Vivo (original) (raw)
Related papers
Activating mutations in Kras are the most frequent mutations in human cancer. They define a subset of patients who do not respond to current therapies and for whom prognosis is poor. Oncogenic Kras has been shown to deregulate numerous signalling pathways of which the most intensively studied are the Ras-ERK cascade and the PI3K-Akt cascade. However, to date there are no effective targeted therapies in the clinic against Kras-mutant cancers. Here we report that the βGBP cytokine, a physiological inhibitor of class I PI3Ks is a potent activator of apoptosis in Kras-mutant colorectal cancer cells, even when co-harboring mutant-activated PIK3CA. Our study unveils an elective route to intrinsic and extrinsic apoptosis which involves the cytoskeleton. Early events are inhibition of PI3K activity and Rac-independent actin rearrangement assignable to phosphoinositide changes at the plasma membrane. Cyclin E deregulation, arrest of DNA synthesis and Chk2 activation underscore events critical to the activation of an intrinsic apoptotic program. Clustering of CD95/Fas death receptors underscore events critical to the activation of extrinsic apoptosis. In nude mice we present the first evidence that xenograft tumor development is strongly inhibited by Hu-r-βGBP. Taken together our results open a new therapeutic opportunity against a subset of patients refractive to current treatments. This first demonstration of therapeutic efficacy against Kras-mutant colon cancer suggests that Hu-r-βGBP may also be therapeutically effective against other cancers harbouring activating Ras mutations as well as PIK3CA mutations.
2016
Activating mutations in Kras are the most frequent mutations in human cancer. They define a subset of patients who do not respond to current therapies and for whom prognosis is poor. Oncogenic Kras has been shown to deregulate numerous signaling pathways of which the most intensively studied are the Ras/ extracellular signal–regulated kinase cascade and the phosphoinositide 3-kinase (PI3K)/Akt cascade. How-ever, to date, there are no effective targeted therapies in the clinic against Kras-mutant cancers. Here, we report that the b-galactoside–binding protein (bGBP) cytokine, a physiologic inhibitor of class I PI3Ks, is a potent activator of apoptosis in Kras-mutant colorectal cancer cells, even when coharboring mutant-activated PIK3CA. Our study unveils an elective route to intrinsic and extrinsic apoptosis, which involves the cytoskeleton. Early events are inhibition of PI3K activity and Rac-independent actin rearrangement assignable to phosphoinositide changes at the plasma membra...
Targeting KRAS in Colorectal Cancer: A Bench to Bedside Review
International Journal of Molecular Sciences
Colorectal cancer (CRC) is a heterogeneous disease with a myriad of alterations at the cellular and molecular levels. Kristen rat sarcoma (KRAS) mutations occur in up to 40% of CRCs and serve as both a prognostic and predictive biomarker. Oncogenic mutations in the KRAS protein affect cellular proliferation and survival, leading to tumorigenesis through RAS/MAPK pathways. Until recently, only indirect targeting of the pathway had been investigated. There are now several KRAS allele-specific inhibitors in late-phase clinical trials, and many newer agents and targeting strategies undergoing preclinical and early-phase clinical testing. The adequate treatment of KRAS-mutated CRC will inevitably involve combination therapies due to the existence of robust adaptive resistance mechanisms in these tumors. In this article, we review the most recent understanding and findings related to targeting KRAS mutations in CRC, mechanisms of resistance to KRAS inhibitors, as well as evolving treatmen...
Research progress on KRAS mutations in colorectal cancer
Journal of Cancer Metastasis and Treatment, 2021
The RAS gene family, responsible for signal transduction within the mitogen activated protein kinase (MAPK) and phosphatidylinositol 3 kinase (PI3K) pathways, is frequently involved in carcinogenesis, and alterations in its member genes can be detected, with variable frequency, in a wide variety of solid and hematological cancers. These alterations may behave as prognostic-predictive biomarkers and driver mutations, making them an interesting therapeutic target. Since their discovery, many strategies have been pursued to act on their signaling pathways. Indeed, in clinical practice, KRAS, the most prominent member of the RAS gene family, represents an especially elusive target in most malignancies; pathway inhibition is carried out upstream, on the EGFR receptor, or downstream, most frequently on the BRAF/MEK/ERK cascade. Recently, clinically relevant direct RAS inhibition has been successfully achieved with the development of potent and selective covalent inhibitors of KRAS c.34G>T (p.G12C). These latest-generation drugs represent both a new and interesting tool in the therapeutic armamentarium and a symbolic end to the myth of KRAS undruggability. However, their clinical relevance and appropriate place in treatment strategies remain to be determined.
Targeting the undruggable oncogenic KRAS: the dawn of hope
JCI Insight
Introduction KRAS is a frequently mutated proto-oncogene that drives epithelial-mesenchymal transition, which leads to tumorigenesis mainly in the lung, colon, and pancreas (1, 2). KRAS belongs to the human RAS gene family that encodes three small GTPases (NRAS, HRAS, and KRAS) that cycle between GTP-bound active and GDP-bound inactive states. KRAS is located on the inner leaflet of the plasma membrane, and active KRAS transduces extracellular signals from receptor tyrosine kinases (RTKs) to downstream signaling pathways, thus controlling cell proliferation, differentiation, transformation, and apoptosis (3). The GTP/GDP molecular switch takes place upon translocation of GEFs and GAPs toward the proximity of KRAS (4). The mutations in the GTP-binding site confer resistance to GTP hydrolysis by GAPs, resulting in constitutively active KRAS (5). Hyperactive KRAS induces oncogenic transformation by upregulating downstream signaling pathways, including PI3K/AKT/mTOR, RAF/ MEK/ERK, MAPK/ERK, and RALGEF/RAL (6). Although RAS proteins exhibit some structural homology and share similar functional and biochemical properties, the oncogenic potential of each RAS isoform varies by the tissue, codon, substitution type, and mutation frequency. More than 80% of mutations in KRAS occur at codon 12, found prevalently as G12D substitution in 70% of pancreatic ductal adenocarcinoma (PDAC) (7) and in almost 50% of colorectal carcinoma (CRC) cases (8). On the other hand, G12C is harbored more frequently in non-small cell lung carcinoma (NSCLC) and is present in approximatively 40% of metastatic lung adenocarcinoma cases (9). From a clinical perspective, KRAS mutants are attractive potential therapeutic targets (10). Thus, numerous efforts have been made over the last 30 years to inhibit mutant KRAS with small molecules. However, attempts to develop GTP analog inhibitors have been challenged by the structural properties of the GTP-binding pocket, high homology between RAS proteins, high affinity between GTP and KRAS, and high concentration of GTP in cells in vivo (11, 12). Alternatively, intensive investigations have been made toward targeting downstream KRAS effectors, including the RAS-binding domain of RAF, the MAPK pathway effector kinases MEK and ERK, and mTOR of the PI3K/AKT pathway (see refs. 12-15 for recent reviews on efforts targeting these pathways). KRAS mutations are the drivers of various cancers, including non-small cell lung cancer, colon cancer, and pancreatic cancer. Over the last 30 years, immense efforts have been made to inhibit KRAS mutants and oncogenic KRAS signaling using inhibitors. Recently, specific targeting of KRAS mutants with small molecules revived the hopes for successful therapies for lung, pancreatic, and colorectal cancer patients. Moreover, advances in gene editing, protein engineering, and drug delivery formulations have revolutionized cancer therapy regimens. New therapies aim to improve immune surveillance and enhance antitumor immunity by precisely targeting cancer cells harboring oncogenic KRAS. Here, we review recent KRAS-targeting strategies, their therapeutic potential, and remaining challenges to overcome. We also highlight the potential synergistic effects of various combinatorial therapies in preclinical and clinical trials.
Journal of Experimental & Clinical Cancer Research
Background: Previous studies showed that the combination of an anti-Epidermal growth factor (EGFR) and a MEKinhibitor is able to prevent the onset of resistance to anti-EGFR monoclonal antibodies in KRAS-wild type colorectal cancer (CRC), while the same combination reverts anti-EGFR primary resistance in KRAS mutated CRC cell lines. However, rapid onset of resistance is a limit to combination therapies in KRAS mutated CRC. Methods: We generated four different KRAS mutated CRC cell lines resistant to a combination of cetuximab (an anti-EGFR antibody) and refametinib (a selective MEK-inhibitor) after continuous exposure to increasing concentration of the drugs. We characterized these resistant cell lines by evaluating the expression and activation status of a panel of receptor tyrosine kinases (RTKs) and intracellular transducers by immunoblot and qRT-PCR. Oncomine comprehensive assay and microarray analysis were carried out to investigate new acquired mutations or transcriptomic adaptation, respectively, in the resistant cell lines. Immunofluorescence assay was used to show the localization of RTKs in resistant and parental clones. Results: We found that PI3K-AKT pathway activation acts as an escape mechanism in cell lines with acquired resistance to combined inhibition of EGFR and MEK. AKT pathway activation is coupled to the activation of multiple RTKs such as HER2, HER3 and IGF1R, though its pharmacological inhibition is not sufficient to revert the resistant phenotype. PI3K pathway activation is mediated by autocrine loops and by heterodimerization of multiple receptors. Conclusions: PI3K activation plays a central role in the acquired resistance to the combination of anti-EGFR and MEKinhibitor in KRAS mutated colorectal cancer cell lines. PI3K activation is cooperatively achieved through the activation of multiple RTKs such as HER2, HER3 and IGF1R.
Therapeutic Targets of KRAS in Colorectal Cancer
Cancers
Patients with metastatic colorectal cancer have a 5-year overall survival of less than 10%. Approximately 45% of patients with metastatic colorectal cancer harbor KRAS mutations. These mutations not only carry a predictive role for the absence of response to anti-EGFR therapy, but also have a negative prognostic impact on the overall survival. There is a growing unmet need for a personalized therapy approach for patients with KRAS-mutant colorectal cancer. In this article, we focus on the therapeutic strategies targeting KRAS- mutant CRC, while reviewing and elaborating on the discovery and physiology of KRAS.