KRAS: feeding pancreatic cancer proliferation Bryant, Kirsten L.; Mancias, Joseph D.; Kimmelman, Alec C. ...
Trends in biochemical sciences,
02/2014, Letnik:
39, Številka:
2
Journal Article
Recenzirano
Odprti dostop
•KRAS is the most frequently mutated gene in PDAC and drives cancer development and growth.•Oncogenic KRAS alters cellular glucose uptake, glycolytic flux, and glutamine usage.•Autophagy and ...macropinocytosis are upregulated by mutant KRAS to assist PDAC survival.•Mechanisms of oncogenic KRAS-driven metabolism may yield new anti-K-Ras therapeutics.
Oncogenic KRAS mutation is the signature genetic event in the progression and growth of pancreatic ductal adenocarcinoma (PDAC), an almost universally fatal disease. Although it has been appreciated for some time that nearly 95% of PDAC harbor mutationally activated KRAS, to date no effective treatments that target this mutant protein have reached the clinic. A number of studies have shown that oncogenic KRAS plays a central role in controlling tumor metabolism by orchestrating multiple metabolic changes including stimulation of glucose uptake, differential channeling of glucose intermediates, reprogrammed glutamine metabolism, increased autophagy, and macropinocytosis. We review these recent findings and address how they may be applied to develop new PDAC treatments.
Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest cancers with a dismal 7% 5-year survival rate and is projected to become the second leading cause of cancer-related deaths by 2020. KRAS ...is mutated in 95% of PDACs and is a well-validated driver of PDAC growth and maintenance. However, despite comprehensive efforts, an effective anti-RAS drug has yet to reach the clinic. Different paths to inhibiting RAS signaling are currently under investigation in the hope of finding a successful treatment. Recently, direct RAS binding molecules have been discovered, challenging the perception that RAS is an "undruggable" protein. Other strategies currently being pursued take an indirect approach, targeting proteins that facilitate RAS membrane association or downstream effector signaling. Unbiased genetic screens have identified synthetic lethal interactors of mutant RAS. Most recently, metabolic targets in pathways related to glycolytic signaling, glutamine utilization, autophagy, and macropinocytosis are also being explored. Harnessing the patient's immune system to fight their cancer is an additional exciting route that is being considered. The "best" path to inhibiting KRAS has yet to be determined, with each having promise as well as potential pitfalls. We will summarize the state-of-the-art for each direction, focusing on efforts directed toward the development of therapeutics for pancreatic cancer patients with mutated KRAS.
Tumor progression involves the ability of cancer cells to communicate with each other and with neighboring normal cells in their microenvironment. Microvesicles (MV) derived from human cancer cells ...have received a good deal of attention because of their ability to participate in the horizontal transfer of signaling proteins between cancer cells and to contribute to their invasive activity. Here we show that MV may play another important role in oncogenesis. In particular, we demonstrate that MV shed by two different human cancer cells, MDAMB231 breast carcinoma cells and U87 glioma cells, are capable of conferring onto normal fibroblasts and epithelial cells the transformed characteristics of cancer cells (e.g., anchorage-independent growth and enhanced survival capability) and that this effect requires the transfer of the protein cross-linking enzyme tissue transglutaminase (tTG). We further demonstrate that tTG is not sufficient to transform fibroblasts but rather that it must collaborate with another protein to mediate the transforming actions of the cancer cell-derived MV. Proteomic analyses of the MV derived from MDAMB231 and U87 cells indicated that both these vesicle preparations contained the tTG-binding partner and cross-inking substrate fibronectin (FN). Moreover, we found that tTG cross-links FN in MV from cancer cells and that the ensuing MV-mediated transfers of cross-linked FN and tTG to recipient fibroblasts function cooperatively to activate mitogenic signaling activities and to induce their transformation. These findings highlight a role for MV in the induction of cellular transformation and identify tTG and FN as essential participants in this process.
Our recent ERK1/2 inhibitor analyses in pancreatic ductal adenocarcinoma (PDAC) indicated ERK1/2-independent mechanisms maintaining MYC protein stability. To identify these mechanisms, we determined ...the signaling networks by which mutant KRAS regulates MYC. Acute KRAS suppression caused rapid proteasome-dependent loss of MYC protein, through both ERK1/2-dependent and -independent mechanisms. Surprisingly, MYC degradation was independent of PI3K-AKT-GSK3β signaling and the E3 ligase FBWX7. We then established and applied a high-throughput screen for MYC protein degradation and performed a kinome-wide proteomics screen. We identified an ERK1/2-inhibition-induced feedforward mechanism dependent on EGFR and SRC, leading to ERK5 activation and phosphorylation of MYC at S62, preventing degradation. Concurrent inhibition of ERK1/2 and ERK5 disrupted this mechanism, synergistically causing loss of MYC and suppressing PDAC growth.
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•Acute suppression of KRAS causes proteasome-dependent degradation of MYC protein•KRAS regulates MYC protein stability by ERK but not by PI3K-AKT effector signaling•ERK1/2-inhibition-induced feedforward activation of EGFR-MEK5-ERK5 blocks MYC loss•Inhibiting ERK1/2 and ERK5 synergistically causes MYC loss and inhibits PDAC growth
Vaseva et al. find that mutant KRAS regulates MYC via ERK1/2-dependent and -independent mechanisms in pancreatic cancer (PDAC). ERK1/2 blockade activates a compensatory EGFR-SRC-ERK5 cascade that stabilizes MYC, and combined ERK1/2 and ERK5 inhibition promotes synergistic loss of MYC and suppresses PDAC growth.
Macroautophagy/autophagy is upregulated in pancreatic ductal adenocarcinoma (PDAC) and PDAC growth is reliant on autophagy. However, autophagy inhibitors as monotherapy have shown limited clinical ...efficacy. To identify targets that sensitize PDAC cells to autophagy inhibition, we performed a CRISPR-Cas9 genetic loss-of-function screen in cells treated with the lysosomal inhibitor chloroquine (CQ) and identified IGF1R as a sensitizer. IGF1R inhibition increases autophagic flux and sensitivity to CQ-mediated growth suppression both in vitro and in vivo. Importantly, sensitization is further enhanced with the concurrent inhibition of MAPK1/ERK2 (mitogen-activated protein kinase 1)-MAPK3/ERK1. IGF1R and MAPK/ERK inhibition converge on suppression of glycolysis. In summary, IGF1R and MAPK/ERK signaling promotes resistance to CQ/HCQ in PDAC, and their dual inhibition increases sensitivity to autophagy inhibitors.
Black, Indigenous, and other Women of Color (BIWOC) are at increased risk for interpersonal trauma, including racial trauma. Interpersonal trauma has potentially deleterious emotional, cognitive, ...physical, social, and spiritual consequences. European models of trauma recovery often end their process with coping strategies and meaning-making; womanist psychology, which emerges from the cultural traditions of Black women's experiences and wisdom, incorporates survivors' adoption of resistance strategies to combat trauma and oppression. The authors present the Resist and Rise model for womanist trauma recovery groups, which frames each component as an act of resistance. Clinical, research, and policy implications are identified.
Induction of compensatory mechanisms and ERK reactivation has limited the effectiveness of Raf and MEK inhibitors in RAS-mutant cancers. We determined that direct pharmacologic inhibition of ERK ...suppressed the growth of a subset of KRAS-mutant pancreatic cancer cell lines and that concurrent phosphatidylinositol 3-kinase (PI3K) inhibition caused synergistic cell death. Additional combinations that enhanced ERK inhibitor action were also identified. Unexpectedly, long-term treatment of sensitive cell lines caused senescence, mediated in part by MYC degradation and p16 reactivation. Enhanced basal PI3K-AKT-mTOR signaling was associated with de novo resistance to ERK inhibitor, as were other protein kinases identified by kinome-wide siRNA screening and a genetic gain-of-function screen. Our findings reveal distinct consequences of inhibiting this kinase cascade at the level of ERK.
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•Bimodal action: differential consequences of short-versus long-term ERK inhibition•ERK inhibitor sensitivity is associated with MYC degradation in vitro and in vivo•PI3K-AKT-mTOR signaling drives basal resistance to ERK inhibitor treatment•Resistance mechanisms are complex and display significant inter-tumor heterogeneity
Hayes et al. report an ERK inhibition-mediated growth suppression mechanism involving MYC degradation that is associated with the induction of a senescence-like phenotype in KRAS-mutant pancreatic cancer cells. Inhibitor combinations that enhance the effect of ERK inhibitor are also identified.
Mutational loss of CDKN2A (encoding p16INK4A) tumor-suppressor function is a key genetic step that complements activation of KRAS in promoting the development and malignant growth of pancreatic ...ductal adenocarcinoma (PDAC). However, pharmacologic restoration of p16INK4A function with inhibitors of CDK4 and CDK6 (CDK4/6) has shown limited clinical efficacy in PDAC. Here, we found that concurrent treatment with both a CDK4/6 inhibitor (CDK4/6i) and an ERK-MAPK inhibitor (ERKi) synergistically suppresses the growth of PDAC cell lines and organoids by cooperatively blocking CDK4/6i-induced compensatory upregulation of ERK, PI3K, antiapoptotic signaling, and MYC expression. On the basis of these findings, a Phase I clinical trial was initiated to evaluate the ERKi ulixertinib in combination with the CDK4/6i palbociclib in patients with advanced PDAC (NCT03454035). As inhibition of other proteins might also counter CDK4/6i-mediated signaling changes to increase cellular CDK4/6i sensitivity, a CRISPR-Cas9 loss-of-function screen was conducted that revealed a spectrum of functionally diverse genes whose loss enhanced CDK4/6i growth inhibitory activity. These genes were enriched around diverse signaling nodes, including cell-cycle regulatory proteins centered on CDK2 activation, PI3K-AKT-mTOR signaling, SRC family kinases, HDAC proteins, autophagy-activating pathways, chromosome regulation and maintenance, and DNA damage and repair pathways. Novel therapeutic combinations were validated using siRNA and small-molecule inhibitor-based approaches. In addition, genes whose loss imparts a survival advantage were identified (e.g., RB1, PTEN, FBXW7), suggesting possible resistance mechanisms to CDK4/6 inhibition. In summary, this study has identified novel combinations with CDK4/6i that may have clinical benefit to patients with PDAC.
CRISPR-Cas9 screening and protein activity mapping reveal combinations that increase potency of CDK4/6 inhibitors and overcome drug-induced compensations in pancreatic cancer.
The small GTPase KRAS is frequently mutated in pancreatic cancer and its cooperation with the transcription factor MYC is essential for malignant transformation. The key to oncogenic KRAS and MYC ...working together is the stabilization of MYC expression due to KRAS activating the extracellular signal–regulated kinase 1/2, which phosphorylates MYC at serine 62 (Ser 62). This prevents the proteasomal degradation of MYC while enhancing its transcriptional activity. Here, we identify how this essential signaling connection between oncogenic KRAS and MYC expression is mediated by the inhibitor of apoptosis protein family member Survivin. This discovery stemmed from our finding that Survivin expression is downregulated upon treatment of pancreatic cancer cells with the KRASG12C inhibitor Sotorasib. We went on to show that oncogenic KRAS increases Survivin expression by activating extracellular signal–regulated kinase 1/2 in pancreatic cancer cells and that treating the cells either with siRNAs targeting Survivin or with YM155, a small molecule that potently blocks Survivin expression, downregulates MYC and strongly inhibited their growth. We further determined that Survivin protects MYC from degradation by blocking autophagy, which then prevents cellular inhibitor of protein phosphatase 2A from undergoing autophagic degradation. Cellular inhibitor of protein phosphatase 2A, by inhibiting protein phosphatase 2A, helps to maintain MYC phosphorylation at Ser 62, thereby ensuring its cooperation with oncogenic KRAS in driving cancer progression. Overall, these findings highlight a novel role for Survivin in mediating the cooperative actions of KRAS and MYC during malignant transformation and raise the possibility that targeting Survivin may offer therapeutic benefits against KRAS-driven cancers.
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