Concurrent inhibition of oncogenic and wild-type RAS-GTP for cancer therapy

RAS oncogenes (collectively NRAS, HRAS and especially KRAS) are among the most frequently mutated genes in cancer, with common driver mutations occurring at codons 12, 13 and 611. Small molecule inhibitors of the KRAS(G12C) oncoprotein have demonstrated clinical efficacy in patients with multiple cancer types and have led to regulatory approvals for the treatment of non-small cell lung cancer2,3. Nevertheless, KRASG12C mutations account for only around 15% of KRAS-mutated cancers4,5, and there are no approved KRAS inhibitors for the majority of patients with tumours containing other common KRAS mutations. Here we describe RMC-7977, a reversible, tri-complex RAS inhibitor with broad-spectrum activity for the active state of both mutant and wild-type KRAS, NRAS and HRAS variants (a RAS(ON) multi-selective inhibitor). Preclinically, RMC-7977 demonstrated potent activity against RAS-addicted tumours carrying various RAS genotypes, particularly against cancer models with KRAS codon 12 mutations (KRASG12X). Treatment with RMC-7977 led to tumour regression and was well tolerated in diverse RAS-addicted preclinical cancer models. Additionally, RMC-7977 inhibited the growth of KRASG12C cancer models that are resistant to KRAS(G12C) inhibitors owing to restoration of RAS pathway signalling. Thus, RAS(ON) multi-selective inhibitors can target multiple oncogenic and wild-type RAS isoforms and have the potential to treat a wide range of RAS-addicted cancers with high unmet clinical need. A related RAS(ON) multi-selective inhibitor, RMC-6236, is currently under clinical evaluation in patients with KRAS-mutant solid tumours (ClinicalTrials.gov identifier: NCT05379985).

TEAD Inhibition Overcomes YAP1/TAZ-Driven Primary and Acquired Resistance to KRASG12C Inhibitors

Primary/intrinsic and treatment-induced acquired resistance limit the initial response rate to and long-term efficacy of direct inhibitors of the KRASG12C mutant in cancer. To identify potential mechanisms of resistance, we applied a CRISPR/Cas9 loss-of-function screen and observed loss of multiple components of the Hippo tumor suppressor pathway, which acts to suppress YAP1/TAZ-regulated gene transcription. YAP1/TAZ activation impaired the antiproliferative and proapoptotic effects of KRASG12C inhibitor (G12Ci) treatment in KRASG12C-mutant cancer cell lines. Conversely, genetic suppression of YAP1/WWTR1 (TAZ) enhanced G12Ci sensitivity. YAP1/TAZ activity overcame KRAS dependency through two distinct TEAD transcription factor-dependent mechanisms, which phenocopy KRAS effector signaling. First, TEAD stimulated ERK-independent transcription of genes normally regulated by ERK (BIRC5, CDC20, ECT2, FOSL1, and MYC) to promote progression through the cell cycle. Second, TEAD caused activation of PI3K-AKT-mTOR signaling to overcome apoptosis. G12Ci treatment-induced acquired resistance was also caused by YAP1/TAZ-TEAD activation. Accordingly, concurrent treatment with pharmacologic inhibitors of TEAD synergistically enhanced KRASG12C inhibitor antitumor activity in vitro and prolonged tumor suppression in vivo. In summary, these observations reveal YAP1/TAZ-TEAD signaling as a crucial driver of primary and acquired resistance to KRAS inhibition and support the use of TEAD inhibitors to enhance the antitumor efficacy of KRAS-targeted therapies.

SIGNIFICANCE

YAP1/TAZ-TEAD activation compensates for loss of KRAS effector signaling, establishing a mechanistic basis for concurrent inhibition of TEAD to enhance the efficacy of KRASG12C-selective inhibitor treatment of KRASG12C-mutant cancers. See related commentary by Johnson and Haigis, p. 4005.

Combination Therapies with CDK4/6 Inhibitors to Treat KRAS-Mutant Pancreatic Cancer

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.

SIGNIFICANCE

CRISPR-Cas9 screening and protein activity mapping reveal combinations that increase potency of CDK4/6 inhibitors and overcome drug-induced compensations in pancreatic cancer.

Functional and biological heterogeneity of KRASQ61 mutations

Missense mutations at the three hotspots in the guanosine triphosphatase (GTPase) RAS-Gly12, Gly13, and Gln61 (commonly known as G12, G13, and Q61, respectively)-occur differentially among the three RAS isoforms. Q61 mutations in KRAS are infrequent and differ markedly in occurrence. Q61H is the predominant mutant (at 57%), followed by Q61R/L/K (collectively 40%), and Q61P and Q61E are the rarest (2 and 1%, respectively). Probability analysis suggested that mutational susceptibility to different DNA base changes cannot account for this distribution. Therefore, we investigated whether these frequencies might be explained by differences in the biochemical, structural, and biological properties of KRASQ61 mutants. Expression of KRASQ61 mutants in NIH 3T3 fibroblasts and RIE-1 epithelial cells caused various alterations in morphology, growth transformation, effector signaling, and metabolism. The relatively rare KRASQ61E mutant stimulated actin stress fiber formation, a phenotype distinct from that of KRASQ61H/R/L/P, which disrupted actin cytoskeletal organization. The crystal structure of KRASQ61E was unexpectedly similar to that of wild-type KRAS, a potential basis for its weak oncogenicity. KRASQ61H/L/R-mutant pancreatic ductal adenocarcinoma (PDAC) cell lines exhibited KRAS-dependent growth and, as observed with KRASG12-mutant PDAC, were susceptible to concurrent inhibition of ERK-MAPK signaling and of autophagy. Our results uncover phenotypic heterogeneity among KRASQ61 mutants and support the potential utility of therapeutic strategies that target KRASQ61 mutant-specific signaling and cellular output.

Concurrent Inhibition of ERK and Farnesyltransferase Suppresses the Growth of HRAS Mutant Head and Neck Squamous Cell Carcinoma

Human papilloma virus (HPV)-negative head and neck squamous cell carcinoma (HNSCC) is a common cancer worldwide with an unmet need for more effective, less toxic treatments. Currently, both the disease and the treatment of HNSCC cause significant mortality and morbidity. Targeted therapies hold new promise for patients with HPV-negative status whose tumors harbor oncogenic HRAS mutations. Recent promising clinical results have renewed interest in the development of farnesyltransferase inhibitors (FTIs) as a therapeutic strategy for HRAS-mutant cancers. With the advent of clinical evaluation of the FTI tipifarnib for the treatment of HRAS-mutant HNSCC, we investigated the activity of tipifarnib and inhibitors of HRAS effector signaling in HRAS-mutant HNSCC cell lines. First, we validated that HRAS is a cancer driver in HRAS-mutant HNSCC lines. Second, we showed that treatment with the FTI tipifarnib largely phenocopied HRAS silencing, supporting HRAS as a key target of FTI antitumor activity. Third, we performed reverse-phase protein array analyses to profile FTI treatment-induced changes in global signaling, and conducted CRISPR/Cas9 genetic loss-of-function screens to identify previously unreported genes and pathways that modulate sensitivity to tipifarnib. Fourth, we determined that concurrent inhibition of HRAS effector signaling (ERK, PI3K, mTORC1) increased sensitivity to tipifarnib treatment, in part by overcoming tipifarnib-induced compensatory signaling. We also determined that ERK inhibition could block tipifarnib-induced epithelial-to-mesenchymal transition, providing a potential basis for the effectiveness of this combination. Our results support future investigations of these and other combination treatments for HRAS mutant HNSCC.

Aberrant Expression and Subcellular Localization of ECT2 Drives Colorectal Cancer Progression and Growth

ECT2 is an activator of RHO GTPases that is essential for cytokinesis. In addition, ECT2 was identified as an oncoprotein when expressed ectopically in NIH/3T3 fibroblasts. However, oncogenic activation of ECT2 resulted from N-terminal truncation, and such truncated ECT2 proteins have not been found in patients with cancer. In this study, we observed elevated expression of full-length ECT2 protein in preneoplastic colon adenomas, driven by increased ECT2 mRNA abundance and associated with APC tumor-suppressor loss. Elevated ECT2 levels were detected in the cytoplasm and nucleus of colorectal cancer tissue, suggesting cytoplasmic mislocalization as one mechanism of early oncogenic ECT2 activation. Importantly, elevated nuclear ECT2 correlated with poorly differentiated tumors, and a low cytoplasmic:nuclear ratio of ECT2 protein correlated with poor patient survival, suggesting that nuclear and cytoplasmic ECT2 play distinct roles in colorectal cancer. Depletion of ECT2 reduced anchorage-independent cancer cell growth and invasion independent of its function in cytokinesis, and loss of Ect2 extended survival in a Kras G12D Apc-null colon cancer mouse model. Expression of ECT2 variants with impaired nuclear localization or guanine nucleotide exchange catalytic activity failed to restore cancer cell growth or invasion, indicating that active, nuclear ECT2 is required to support tumor progression. Nuclear ECT2 promoted ribosomal DNA transcription and ribosome biogenesis in colorectal cancer. These results support a driver role for both cytoplasmic and nuclear ECT2 overexpression in colorectal cancer and emphasize the critical role of precise subcellular localization in dictating ECT2 function in neoplastic cells. SIGNIFICANCE: ECT2 overexpression and mislocalization support its role as a driver in colon cancer that is independent from its function in normal cell cytokinesis.

CHK1 protects oncogenic KRAS-expressing cells from DNA damage and is a target for pancreatic cancer treatment

We apply genetic screens to delineate modulators of KRAS mutant pancreatic ductal adenocarcinoma (PDAC) sensitivity to ERK inhibitor treatment, and we identify components of the ATR-CHK1 DNA damage repair (DDR) pathway. Pharmacologic inhibition of CHK1 alone causes apoptotic growth suppression of both PDAC cell lines and organoids, which correlates with loss of MYC expression. CHK1 inhibition also activates ERK and AMPK and increases autophagy, providing a mechanistic basis for increased efficacy of concurrent CHK1 and ERK inhibition and/or autophagy inhibition with chloroquine. To assess how CHK1 inhibition-induced ERK activation promotes PDAC survival, we perform a CRISPR-Cas9 loss-of-function screen targeting direct/indirect ERK substrates and identify RIF1. A key component of non-homologous end joining repair, RIF1 suppression sensitizes PDAC cells to CHK1 inhibition-mediated apoptotic growth suppression. Furthermore, ERK inhibition alone decreases RIF1 expression and phenocopies RIF1 depletion. We conclude that concurrent DDR suppression enhances the efficacy of ERK and/or autophagy inhibitors in KRAS mutant PDAC.

Targeting p130Cas- and microtubule-dependent MYC regulation sensitizes pancreatic cancer to ERK MAPK inhibition

To identify therapeutic targets for KRAS mutant pancreatic cancer, we conduct a druggable genome small interfering RNA (siRNA) screen and determine that suppression of BCAR1 sensitizes pancreatic cancer cells to ERK inhibition. Integrative analysis of genome-scale CRISPR-Cas9 screens also identify BCAR1 as a top synthetic lethal interactor with mutant KRAS. BCAR1 encodes the SRC substrate p130Cas. We determine that SRC-inhibitor-mediated suppression of p130Cas phosphorylation impairs MYC transcription through a DOCK1-RAC1-β-catenin-dependent mechanism. Additionally, genetic suppression of TUBB3, encoding the βIII-tubulin subunit of microtubules, or pharmacological inhibition of microtubule function decreases levels of MYC protein in a calpain-dependent manner and potently sensitizes pancreatic cancer cells to ERK inhibition. Accordingly, the combination of a dual SRC/tubulin inhibitor with an ERK inhibitor cooperates to reduce MYC protein and synergistically suppress the growth of KRAS mutant pancreatic cancer. Thus, we demonstrate that mechanistically diverse combinations with ERK inhibition suppress MYC to impair pancreatic cancer proliferation.

Low-Dose Vertical Inhibition of the RAF-MEK-ERK Cascade Causes Apoptotic Death of KRAS Mutant Cancers

We address whether combinations with a pan-RAF inhibitor (RAFi) would be effective in KRAS mutant pancreatic ductal adenocarcinoma (PDAC). Chemical library and CRISPR genetic screens identify combinations causing apoptotic anti-tumor activity. The most potent combination, concurrent inhibition of RAF (RAFi) and ERK (ERKi), is highly synergistic at low doses in cell line, organoid, and rat models of PDAC, whereas each inhibitor alone is only cytostatic. Comprehensive mechanistic signaling studies using reverse phase protein array (RPPA) pathway mapping and RNA sequencing (RNA-seq) show that RAFi/ERKi induced insensitivity to loss of negative feedback and system failures including loss of ERK signaling, FOSL1, and MYC; shutdown of the MYC transcriptome; and induction of mesenchymal-to-epithelial transition. We conclude that low-dose vertical inhibition of the RAF-MEK-ERK cascade is an effective therapeutic strategy for KRAS mutant PDAC.

Abstract B15: CRISPR/Cas9 genetic screen identifies novel therapeutic strategies for treating HRAS mutant HNSCC with farnesyltransferase inhibitors (FTIs)

Head and neck squamous cell carcinoma (HNSCC) affects more than 50,000 people annually. The five-year survival rate has not improved significantly in the last decades. In addition, many treatment modalities are associated with significant morbidity that negatively impacts survivors’ quality of life. Mutations in the HRAS oncogene are presented in 5-10% cases of HNSCC. Our group has established its critical importance for the growth and survival of HNSCC. HRAS protein undergoes crucial post-translational modifications prompted by the obligate addition of a farnesyl isoprenoid group, which is required for proper localization and insertion into the cell membrane, where it can engage effector molecules. FTIs block farnesylation and thus block HRAS activity. The FTI tipifarnib is under clinical evaluation for the treatment of HRAS mutant HNSCC, and preliminary findings showed some efficacy in this patient population. We sought strategies to enhance the efficacy of tipifarnib for the treatment of HRAS mutant HNSCC. We applied a novel CRISPR/Cas9 genetic screen to identify druggable targets that could be inhibited in combination with FTIs to improve treatment outcomes. We identified genes involved in regulating the ERK-MAPK and PI3K-AKT effector signaling pathways, autophagy regulation, chemokine signaling, and chromatin structure, that could potentially be targeted to increase tumor sensitivity to tipifarnib. Consistent with our genetic screening result of enhanced vulnerability to autophagy inhibition in tipifarnib-treated cells, we observed an increase in autophagic flux upon short-term treatment with tipifarnib alone, suggesting an attempt to compensate for nutrient stress. To overcome this effect, we tested the consequences of inhibiting autophagy pharmacologically in combination with tipifarnib. A panel of HRAS mutant HNSCC cell lines showed a synergistic increase in sensitivity to tipifarnib in combination with SBI-0206965 and MRT68921, two distinct preclinical inhibitors of the autophagy-promoting kinase ULK1. Clinical candidate ULK inhibitors are on the horizon. We suggest that the combination of tipifarnib with ULK inhibitors could be useful to sensitize HRAS mutant HNSCC to tipifarnib. Additional validation and mechanistic experiments are ongoing.

Citation Format: Sehrish-Javaid, Craig M. Goodwin, Kirsten L. Bryant, Samuel D. George, Victoria V. Nguyen, Kathryn N. Lambert, Andrew M. Waters, Channing J. Der, Adrienne D. Cox. CRISPR/Cas9 genetic screen identifies novel therapeutic strategies for treating HRAS mutant HNSCC with farnesyltransferase inhibitors (FTIs) [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr B15.

Author Correction: Combination of ERK and autophagy inhibition as a treatment approach for pancreatic cancer

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Abstract B40: Role of mutant HRAS in growth and drug sensitivity of head and neck squamous cell cancers (HNSCC)

Activating mutations in the HRAS oncogene are present in 5-11% of head and neck squamous cell cancers (HNSCC). We set out to determine if HRAS is a driver of HNSCC growth and whether pharmacologic inhibitors of HRAS membrane association and/or RAS effector signaling may have therapeutic value in these cancers. To determine the importance of HRAS, we depleted it genetically from HRAS-mutant HNSCC cell lines by shRNA and evaluated the effects on cell growth and survival. To determine the potential therapeutic value of blocking HRAS membrane association and/or signaling through the key RAS effector, ERK MAPK, we treated HNSCC cells with inhibitors of farnesyltransferase (FTIs, tipifarnib and lonafarnib) or ERK1/2 (ERKi, SCH772984), respectively. We monitored target inhibition by aqueous/detergent fractionation, gel shift and immunoblotting; quantitated cell viability by Alamar blue assay; and assessed cell cycle distribution and apoptosis by flow cytometry. We found that genetic depletion of mutant HRAS inhibited the growth of HRAS-mutant HNSCC cell lines in vitro, caused a modest G1 cell cycle arrest and robustly induced apoptosis. Since genetic depletion is not clinically feasible, we wished to identify targeted therapies suitable for this patient population. Several cancer types driven by mutant RAS are sensitive to inhibitors of the ERK pathway downstream of RAS, and HRAS is the sole RAS isoform whose activity is blocked by FTIs. We found that FTIs and ERKi each inhibited their respective targets at nanomolar range but only FTIs inhibited the growth of HRAS-mutant HNSCC in a target-dependent manner. In cell lines where FTI treatment upregulated ERK signaling, ERKi enhanced sensitivity to FTI. We established that genetic suppression of mutant HRAS blocks HNSCC growth, validating HRAS as a potential therapeutic target. HRAS-mutant HNSCC cell lines are sensitive to FTI but, surprisingly, less sensitive to ERKi. The combination of FTI and ERKi may further sensitize a subset of HRAS-mutant HNSCC. Other targeted combinations will also be discussed.

Citation Format: Sehrish Javaid, Andrew M. Waters, Victoria V. Nguyen, Channing J. Der, Adrienne D. Cox. Role of mutant HRAS in growth and drug sensitivity of head and neck squamous cell cancers (HNSCC) [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr B40.

Atypical KRASG12R Mutant Is Impaired in PI3K Signaling and Macropinocytosis in Pancreatic Cancer

Allele-specific signaling by different KRAS alleles remains poorly understood. The KRAS ^G12R mutation displays uneven prevalence among cancers that harbor the highest occurrence of KRAS mutations: It is rare (∼1%) in lung and colorectal cancers, yet relatively common (∼20%) in pancreatic ductal adenocarcinoma (PDAC), suggesting context-specific properties. We evaluated whether KRAS^G12R is functionally distinct from the more common KRAS^G12D- or KRAS^G12V-mutant proteins (KRAS^G12D/V). We found that KRAS^G12D/V but not KRAS^G12R drives macropinocytosis and that MYC is essential for macropinocytosis in KRAS^G12D/V- but not KRAS^G12R-mutant PDAC. Surprisingly, we found that KRAS^G12R is defective for interaction with a key effector, p110α PI3K (PI3Kα), due to structural perturbations in switch II. Instead, upregulated KRAS-independent PI3Kγ activity was able to support macropinocytosis in KRAS^G12R-mutant PDAC. Finally, we determined that KRAS^G12R-mutant PDAC displayed a distinct drug sensitivity profile compared with KRAS^G12D-mutant PDAC but is still responsive to the combined inhibition of ERK and autophagy. SIGNIFICANCE: We determined that KRAS^G12R is impaired in activating a key effector, p110α PI3K. As such, KRAS^G12R is impaired in driving macropinocytosis. However, overexpression of PI3Kγ in PDAC compensates for this deficiency, providing one basis for the prevalence of this otherwise rare KRAS mutant in pancreatic cancer but not other cancers.See related commentary by Falcomatà et al., p. 23.This article is highlighted in the In This Issue feature, p. 1.

Abstract LB-287: Combination therapies with CDK4/6 inhibitors to treat KRAS-mutant pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) patients have a dismal five-year survival rate of just eight percent in the advanced metastatic setting. Outcomes with standard chemotherapy regimens are less than ideal; therefore, the development of targeted therapies for the treatment of PDAC is a significant unmet clinical need. The two most frequent genetic events in PDAC (mutational activation of KRAS and loss of the tumor suppressor CDKN2A) converge on activation of the kinases CDK4 and CDK6, which promote G1 cell cycle progression. While clinically relevant agents directly targeting KRAS in PDAC remain elusive, pharmacologic restoration of CDKN2A function by inhibition of CDK4/6 may be an effective anti-KRAS therapeutic strategy. Supporting this hypothesis, we found that CDK4/6 inhibitors (e.g., palbociclib, abemaciclib, lerociclib) elicited single-agent activity in a subset of tested PDAC cell lines. However, using Reverse Phase Protein Array (RPPA), we observed widespread compensatory changes that overcome CDK4/6 inhibition, including increased anti-apoptotic protein expression, PI3K-mTOR and ERK MAPK signaling. Concurrent treatment with the potent and selective ERK1/2 inhibitor (ERKi) SCH772984 reversed resistance and increased sensitivity to palbociclib. This combination caused synergistic reduction in anchorage-dependent cell growth, and increased apoptosis, G1 arrest, and senescence. In an organoid model of pancreatic cancer, cell viability was synergistically reduced and caspase activation enhanced. We have also evaluated the combination of ERKi with palbociclib or the clinical-stage CDK4/6 inhibitor lerociclib (G1T38) in mouse models of PDAC, supporting our initiation of a phase Ib clinical trial of the ERK inhibitor ulixertinib/BVD-523 in combination with palbociclib in advanced metastatic pancreatic cancer (NCT03454035). Next, we sought to identify additional genes that regulate sensitivity to CDK4/6 inhibition. Using a CRISPR/Cas9 loss-of-function screen, we individually silenced expression of 2500 genes from the “druggable genome” in combination with palbociclib in six KRAS-mutant pancreatic and two KRAS-mutant colorectal cancer cell lines. We identified a wide array of genes that enhanced growth suppression in combination, centered around diverse signaling nodes including PI3K-AKT-mTOR signaling, cell cycle regulation and mitosis, SRC family kinase signaling, cell metabolism and biosynthesis, chromosome regulation and maintenance, and DNA damage & repair pathways, suggesting novel small molecule combinations to overcome de novo or acquired CDK4/6 inhibitor resistance in the clinic. We also identified genes whose loss imparts a survival advantage, suggesting possible resistance mechanisms to single-agent CDK4/6 inhibition. In total, these data suggest that CDK4/6 inhibitors alone, or in combination, may benefit PDAC patients clinically.

Citation Format: Craig M. Goodwin, Sehrish Javaid, Andrew M. Waters, Bjoern Papke, Runying Yang, Mariaelena Pierobon, Daniel M. Freed, Patrick J. Roberts, Adrienne D. Cox, Kris C. Wood, Emanuel F. Petricoin, Autumn J. McRee, Channing J. Der. Combination therapies with CDK4/6 inhibitors to treat KRAS-mutant pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-287.

Abstract LB-276: Farnesyltransferase inhibitor (FTI)-induced growth inhibition of HRAS-mutant head and neck cancers is enhanced by concurrently inhibiting compensatory upregulation of the ERK-MAPK kinase cascade

Activating mutations in the HRAS oncogene are present in 5-11% of head and neck squamous cell carcinomas (HNSCC), but whether mutant HRAS drives HNSCC growth was not known. The clinical candidate FTI, tipifarnib, is currently under investigation in HRAS-mutant HNSCC, but whether patient responses to tipifarnib are due to blocking HRAS membrane association or due to action on another FTI target/s is also unclear. We found that the FTIs tipifarnib and lonafarnib inhibited the growth of HRAS-mutant HNSCC in a target-dependent manner, blocking HRAS farnesylation and membrane association. We also found that genetic depletion of mutant HRAS inhibited the anchorage-dependent and -independent growth of HRAS-mutant HNSCC cell lines in vitro and robustly induced apoptosis, indicating HNSCC dependence on mutant HRAS and a correlation between FTI-mediated growth inhibition and blockade of HRAS function. Tumor types driven by other RAS isoforms, such as KRAS-driven pancreatic cancer, are highly dependent on the ERK MAPK effector pathway and are sensitive to pharmacological inhibitors of ERK1/2 (ERKi: SCH772984, BVD-523). In contrast, we found that HRAS-driven HNSCC was resistant to growth inhibition by ERKi alone, despite strong target inhibition as indicated by decreases in pRSK and MYC protein levels. Consistent with this finding, genetic depletion of HRAS not only failed to reduce MAPK signaling but instead caused compensatory upregulation. Similarly, FTI treatment also induced upregulation of MAPK signaling, which is typically growth-promoting. We therefore speculated that the addition of ERKi would enhance responses to FTIs, and indeed found that ERKi synergistically enhanced FTI-mediated apoptosis and growth inhibition. Our results provide a mechanistic rationale for adding ERKi to FTI to improve clinical responses in HRAS-mutant HNSCC, and suggest that monitoring MAPK pathway activation may be a useful marker for emerging FTI resistance in this patient population.

Citation Format: Sehrish Javaid, Victoria V. Nguyen, Andrew M. Waters, Craig M. Goodwin, Channing J. Der, Adrienne D. Cox. Farnesyltransferase inhibitor (FTI)-induced growth inhibition of HRAS-mutant head and neck cancers is enhanced by concurrently inhibiting compensatory upregulation of the ERK-MAPK kinase cascade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-276.

Differential Effector Engagement by Oncogenic KRAS

KRAS can bind numerous effector proteins, which activate different downstream signaling events. The best known are RAF, phosphatidylinositide (PI)-3' kinase, and RalGDS families, but many additional direct and indirect effectors have been reported. We have assessed how these effectors contribute to several major phenotypes in a quantitative way, using an arrayed combinatorial siRNA screen in which we knocked down 41 KRAS effectors nodes in 92 cell lines. We show that every cell line has a unique combination of effector dependencies, but in spite of this heterogeneity, we were able to identify two major subtypes of KRAS mutant cancers of the lung, pancreas, and large intestine, which reflect different KRAS effector engagement and opportunities for therapeutic intervention.

Combination of ERK and autophagy inhibition as a treatment approach for pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is characterized by KRAS- and autophagy-dependent tumorigenic growth, but the role of KRAS in supporting autophagy has not been established. We show that, to our surprise, suppression of KRAS increased autophagic flux, as did pharmacological inhibition of its effector ERK MAPK. Furthermore, we demonstrate that either KRAS suppression or ERK inhibition decreased both glycolytic and mitochondrial functions. We speculated that ERK inhibition might thus enhance PDAC dependence on autophagy, in part by impairing other KRAS- or ERK-driven metabolic processes. Accordingly, we found that the autophagy inhibitor chloroquine and genetic or pharmacologic inhibition of specific autophagy regulators synergistically enhanced the ability of ERK inhibitors to mediate antitumor activity in KRAS-driven PDAC. We conclude that combinations of pharmacologic inhibitors that concurrently block both ERK MAPK and autophagic processes that are upregulated in response to ERK inhibition may be effective treatments for PDAC.

KRAS: The Critical Driver and Therapeutic Target for Pancreatic Cancer

RAS genes (HRAS, KRAS, and NRAS) comprise the most frequently mutated oncogene family in human cancer. With the highest RAS mutation frequencies seen with the top three causes of cancer deaths in the United States (lung, colorectal, and pancreatic cancer), the development of anti-RAS therapies is a major priority for cancer research. Despite more than three decades of intense effort, no effective RAS inhibitors have yet to reach the cancer patient. With bitter lessons learned from past failures and with new ideas and strategies, there is renewed hope that undruggable RAS may finally be conquered. With the KRAS isoform mutated in 84% of all RAS-mutant cancers, we focus on KRAS. With a near 100% KRAS mutation frequency, pancreatic ductal adenocarcinoma (PDAC) is considered the most RAS-addicted of all cancers. We review the role of KRAS as a driver and therapeutic target in PDAC.

Evaluation of the selectivity and sensitivity of isoform- and mutation-specific RAS antibodies

There is intense interest in developing therapeutic strategies for RAS proteins, the most frequently mutated oncoprotein family in cancer. Development of effective anti-RAS therapies will be aided by the greater appreciation of RAS isoform-specific differences in signaling events that support neoplastic cell growth. However, critical issues that require resolution to facilitate the success of these efforts remain. In particular, the use of well-validated anti-RAS antibodies is essential for accurate interpretation of experimental data. We evaluated 22 commercially available anti-RAS antibodies with a set of distinct reagents and cell lines for their specificity and selectivity in recognizing the intended RAS isoforms and mutants. Reliability varied substantially. For example, we found that some pan- or isoform-selective anti-RAS antibodies did not adequately recognize their intended target or showed greater selectivity for another; some were valid for detecting G12D and G12V mutant RAS proteins in Western blotting, but none were valid for immunofluorescence or immunohistochemical analyses; and some antibodies recognized nonspecific bands in lysates from "Rasless" cells expressing the oncoprotein BRAF^V600E Using our validated antibodies, we identified RAS isoform-specific siRNAs and shRNAs. Our results may help to ensure the accurate interpretation of future RAS studies.

Comparative proteomics of a model MCF10A-KRasG12V cell line reveals a distinct molecular signature of the KRasG12V cell surface

Oncogenic Ras mutants play a major role in the etiology of most aggressive and deadly carcinomas in humans. In spite of continuous efforts, effective pharmacological treatments targeting oncogenic Ras isoforms have not been developed. Cell-surface proteins represent top therapeutic targets primarily due to their accessibility and susceptibility to different modes of cancer therapy. To expand the treatment options of cancers driven by oncogenic Ras, new targets need to be identified and characterized at the surface of cancer cells expressing oncogenic Ras mutants. Here, we describe a mass spectrometry–based method for molecular profiling of the cell surface using KRas^G12V transfected MCF10A (MCF10A-KRas^G12V) as a model cell line of constitutively activated KRas and native MCF10A cells transduced with an empty vector (EV) as control. An extensive molecular map of the KRas surface was achieved by applying, in parallel, targeted hydrazide-based cell-surface capturing technology and global shotgun membrane proteomics to identify the proteins on the KRas^G12V surface. This method allowed for integrated proteomic analysis that identified more than 500 cell-surface proteins found unique or upregulated on the surface of MCF10A-KRas^G12V cells. Multistep bioinformatic processing was employed to elucidate and prioritize targets for cross-validation. Scanning electron microscopy and phenotypic cancer cell assays revealed changes at the cell surface consistent with malignant epithelial-to-mesenchymal transformation secondary to KRas^G12V activation. Taken together, this dataset significantly expands the map of the KRas^G12V surface and uncovers potential targets involved primarily in cell motility, cellular protrusion formation, and metastasis.

Single Synonymous Mutations in KRAS Cause Transformed Phenotypes in NIH3T3 Cells

Synonymous mutations in the KRAS gene are clustered at G12, G13, and G60 in human cancers. We constructed 9 stable NIH₃T₃ cell lines expressing KRAS, each with one of these synonymous mutations. Compared to the negative control cell line expressing the wild type human KRAS gene, all the synonymous mutant lines expressed more KRAS protein, grew more rapidly and to higher densities, and were more invasive in multiple assays. Three of the cell lines showed dramatic loss of contact inhibition, were more refractile under phase contrast, and their refractility was greatly reduced by treatment with trametinib. Codon usage at these glycines is highly conserved in KRAS compared to HRAS, indicating selective pressure. These transformed phenotypes suggest that synonymous mutations found in driver genes such as KRAS may play a role in human cancers.

Delirium affects length of hospital stay after lung transplantation

BACKGROUND

Delirium is relatively common after lung transplantation, although its prevalence and prognostic significance have not been systematically studied. The purpose of the present study was to examine pretransplant predictors of delirium and the short-term impact of delirium on clinical outcomes among lung transplant recipients.

METHODS

Participants underwent pretransplant cognitive testing using the Repeatable Battery for the Assessment of Neuropsychological Status and the Trail Making Test. After transplant, delirium was assessed using the Confusion Assessment Method until discharge.

RESULTS

Sixty-three patients were transplanted between March and November 2013, of which 23 (37%) developed delirium. Among transplanted patients, 48 patients completed pretransplant cognitive testing. Better pretransplant cognitive function was associated with lower risk of delirium (odds ratio, 0.69 [95% confidence interval 0.48, 0.99], P = .043); and demographic and clinical features including native disease (P = .236), the Charlson comorbidity index (P = .581), and the lung allocation score (P = .871) were unrelated to risk of delirium, although there was a trend for women to experience delirium less frequently (P = .071). The presence (P = .006) and duration (P = .027) of delirium were both associated with longer hospital stays.

CONCLUSION

Delirium occurs in more than one-third of patients after lung transplantation. Delirium was associated with poorer pretransplant cognitive functioning and longer hospital stays, after accounting for other medical and demographic factors.

Biased attention to threat in paediatric anxiety disorders (generalized anxiety disorder, social phobia, specific phobia, separation anxiety disorder) as a function of 'distress' versus 'fear' diagnostic categorization

BACKGROUND

Structural models of emotional disorders propose that anxiety disorders can be classified into fear and distress disorders. Sources of evidence for this distinction come from genetic, self-report and neurophysiological data from adults. The present study examined whether this distinction relates to cognitive processes, indexed by attention bias towards threat, which is thought to cause and maintain anxiety disorders.

METHOD

Diagnostic and attention bias data were analysed from 435 children between 5 and 13 years of age; 158 had principal fear disorder (specific phobia, social phobia or separation anxiety disorder), 75 had principal distress disorder (generalized anxiety disorder, GAD) and 202 had no psychiatric disorder. Anxious children were a clinic-based treatment-seeking sample. Attention bias was assessed on a visual-probe task with angry, neutral and happy faces.

RESULTS

Compared to healthy controls, children with principal distress disorder (GAD) showed a significant bias towards threat relative to neutral faces whereas children with principal fear disorder showed an attention bias away from threat relative to neutral faces. Overall, children displayed an attention bias towards happy faces, irrespective of diagnostic group.

CONCLUSIONS

Our findings support the distinction between fear and distress disorders, and extend empirically derived structural models of emotional disorders to threat processing in childhood, when many anxiety disorders begin and predict lifetime impairment.

Antitumor effects of synthetic 6,7-annulated-4-substituted indole compounds in L1210 leukemic cells in vitro

BACKGROUND

Because annulated indoles have almost no representation in the PubChem or MLSMR databases, an unprecedented class of an indole-based library was constructed, using the indole aryne methodology, and screened for antitumor activity. Sixty-six novel 6,7-annulated-4-substituted indole compounds were synthesized, using a strategic combination of 6,7-indolyne cycloaddition and cross-coupling reactions under both Suzuki-Miyaura and Buchwald-Hartwig conditions, and tested for their effectiveness against murine L1210 tumor cell proliferation in vitro.

MATERIALS AND METHODS

Various markers of tumor cell metabolism, DNA degradation, mitotic disruption, cytokinesis and apoptosis were assayed in vitro to evaluate drug cytotoxicity.

RESULTS

Most compounds inhibited the metabolic activity of leukemic cells in a time- and concentration-dependent manner but only 9 of them were sufficiently potent to inhibit L1210 tumor cell proliferation by 50% in the low-μM range after 2 (IC(50): 4.5-20.4 μM) and 4 days (0.5-4.0 μM) in culture. However, the antiproliferative compounds that were the most effective at day 4 were not necessarily the most potent at day 2, suggesting different speeds of action. A 3-h treatment with antiproliferative annulated indole was sufficient to inhibit, in a concentration-dependent manner, the rate of DNA synthesis measured in L1210 cells over a 0.5-h period of pulse-labeling with (3)H-thymidine. Four of the antiproliferative compounds had weak DNA-binding activities but one compound reduced the fluorescence of the ethidium bromide-DNA complex by up to 53%, suggesting that some annulated indoles might directly interact with double-stranded DNA to disrupt its integrity and prevent the dye from intercalating into DNA base pairs. However, all 9 antiproliferative compounds induced DNA cleavage at 24 h in L1210 cells, containing (3)H-thymidine-prelabeled DNA, suggesting that these antitumor annulated indoles might trigger an apoptotic pathway of DNA fragmentation. Indeed the antiproliferative annulated indoles caused a time-dependent increase of caspase-3 activity with a peak at 6 h. Interestingly, the compounds with the most potent antiproliferative IC(50) values at day 2 were consistently the most effective at inhibiting DNA synthesis at 3 h and inducing DNA fragmentation at 24 h. After 24-48 h, antiproliferative concentrations of annulated indoles increased the mitotic index of L1210 cells and stimulated the formation of many bi-nucleated cells, multi-nucleated cells, apoptotic cells and micronuclei, suggesting that these antitumor compounds might enhance mitotic abnormality, induce chromosomal damage or missegregation, and block cytokinesis to induce apoptosis.

CONCLUSION

Although annulated indoles may have interesting bioactivity, novel derivatives with different substitutions must be synthesized to elucidate structure-activity relationships, identify more potent antitumor lead compounds, and investigate their molecular targets and mechanisms of action.

Bioactivity of synthetic 2-halo-3-aryl-4(3H)-quinazoliniminium halides in L1210 leukemia and SK-BR-3 mammary tumor cells in vitro

BACKGROUND

Because quinazolines and their derivatives exhibit a wide range of pharmacological profiles, there is a continuous interest among synthetic and medicinal chemists in the discovery of more potent analogs. Ten novel quinazoliniminium salts were synthesized and tested for their effectiveness against murine and human tumor cell proliferation in vitro.

MATERIALS AND METHODS

Various markers of tumor cell metabolism, DNA degradation and mitotic disruption were assayed in vitro to evaluate drug cytotoxicity.

RESULTS

All compounds induced concentration- and time-dependent antitumor effects in vitro but the 2-chloro-3-(4-methoxyphenyl)quinazolin-4(3H)-iminium chloride (4) was the most effective inhibitor of leukemia L1210 cell proliferation at days 2-4 (IC50: 2.1-0.9 μM), suggesting that the para-methoxyphenyl substituent on the N3 of 4 may enhance the antiproliferative properties of the quinazoliniminium scaffold. In mammary SK-BR-3 tumor cells, 4 reduced the Ki-67 marker of cell proliferation at 24 h and the metabolic activity at days 2 and 4. Moreover, a 1.5- or 3-h treatment with 4 was sufficient to inhibit the rates of DNA, RNA and protein syntheses measured in L1210 cells over 0.5- or 1-h periods of pulse-labeling with 3H-thymidine, 3H-uridine and 3H-leucine, respectively. As 4 did not reduce the fluorescence of the ethidium bromide-DNA complex, this compound was unlikely to directly bind to or destabilize double-stranded DNA. However, 4 induced DNA cleavage at 24 h in L1210 cells containing 3H-thymidine-prelabeled DNA, suggesting that this antitumor drug might trigger an apoptotic pathway of DNA fragmentation. After 12-48 h, 4 weakly increased the mitotic index of L1210 cells but stimulated the formation of many binucleated cells, multinucleated cells and micronuclei, suggesting that this antitumor compound might enhance mitotic abnormality, induce chromosomal damage or missegregation, and block cytokinesis.

CONCLUSION

Although 4 may have interesting bioactivity, more compounds based on the quinazoliniminium scaffold must be synthesized to elucidate structure-activity relationships, identify more potent antitumor lead compounds, and investigate their molecular targets and mechanisms of action.

Neuroticism as a common dimension in the internalizing disorders

BACKGROUND

Several theories have posited a common internalizing factor to help account for the relationship between mood and anxiety disorders. These disorders are often co-morbid and strongly covary. Other theories and data suggest that personality traits may account, at least in part, for co-morbidity between depression and anxiety. The present study examined the relationship between neuroticism and an internalizing dimension common to mood and anxiety disorders.

METHOD

A sample of ethnically diverse adolescents (n=621) completed self-report and peer-report measures of neuroticism. Participants also completed the Structured Clinical Interview for DSM-IV (SCID).

RESULTS

Structural equation modeling showed that a single internalizing factor was common to lifetime diagnosis of mood and anxiety disorders, and this internalizing factor was strongly correlated with neuroticism. Neuroticism had a stronger correlation with an internalizing factor (r=0.98) than with a substance use factor (r=0.29). Therefore, neuroticism showed both convergent and discriminant validity.

CONCLUSIONS

These results provide further evidence that neuroticism is a necessary factor in structural theories of mood and anxiety disorders. In this study, the correlation between internalizing psychopathology and neuroticism approached 1.0, suggesting that neuroticism may be the core of internalizing psychopathology. Future studies are needed to examine this possibility in other populations, and to replicate our findings.

Successful renal transplantation in factor H autoantibody associated HUS with CFHR1 and 3 deficiency and CFH variant G2850T

Factor H (CFH) autoantibodies are associated with atypical hemolytic uremic syndrome (aHUS). Peritransplantation plasma exchange therapy and intensification of immunosuppression, with adjuvant use of anti-CD20 monoclonal antibodies has recently been advocated for cases of CFH-autoantibody associated aHUS. In this report, we describe successful deceased donor renal transplantation in a case of CFH-autoantibody associated aHUS with combined CFHR1 and 3 deficiency in addition to the CFH sequence variant, (cG2850T, pGln950His). CFH-autoantibodies were detected 2 weeks prior to transplantation. Disease recurrence was not observed using basiliximab, an IL2-receptor antagonist and high-dose corticosteroids with mycophenolate mofetil. Adjuvant therapies such as Rituximab nor intensification of plasma therapy were employed. Consequently, careful consideration needs to be given to the use of additional immunosuppression in certain cases of CFH-autoantibody associated aHUS. Serial measurement of CFH-autoantibodies is required in the immediate pre- and posttransplantation period to further clarify their role as a factor in the recurrence of aHUS posttransplantation. Furthermore, delineation of the functional significance of CFH-autoantibodies is warranted in individual cases.

eTriage--a novel, web-based triage and booking service: enabling timely access to sexual health clinics

In recent years, the sexual health of the nation has risen in profile. We face increasing demands and targets, in particular the 48-hour waiting time directive, and as a result clinic access has become a priority. eTriage is a novel, secure, web-based service designed specifically to increase access to our clinics. It has proved a popular booking method, providing access to 10% of all appointments across the Directorate within six months of introduction. KC60 analyses revealed that the majority of users (58%) underwent asymptomatic screening with the remainder having some degree of pathology. There was a greater percentage prevalence of human papilloma virus, chlamydia, non-specific urethritis, gonorrhoea, herpes and trichomonas in the eTriage population when compared with the general clinic population. A notes review illustrated a high degree of concordance between data entered on eTriage registration and clinical review (97%). A patient survey revealed high levels of patient satisfaction with the service. As an adjunct to our existing booking services, eTriage has served to increase patient choice and has proved itself to be a safe, efficient and effective means of improving patient access.

HIV opt-out increases HIV testing in low-risk patients

We audited the effect of introducing HIV opt-out in a genitourinary medicine clinic in central London, UK. We found that opt-out increased the rate at which HIV testing was offered to low-risk patients and that more tests were done.

Effect of nutrition improvement project on morbidity from infectious diseases in preschool children in Vietnam: comparison with control commune

OBJECTIVE

To evaluate the effect of a nutrition improvement project based on home garden production and nutrition education on morbidity from acute respiratory infection and diarrhoeal disease in preschool children.

DESIGN

The morbidity survey comprised five data collections undertaken by trained interviewers to ascertain the incidence and severity of respiratory infections and the incidence of diarrhoeal disease in children in two communes.

SETTING

A project commune and a control commune in Vietnam.

SUBJECTS

Preschool children to 6 years of age living in the project commune Khai Xuan (average 469 children) and the control commune Ching Cong (average 251 children).

MAIN OUTCOME MEASURES

Differences between the two communes over time in the incidence and severity of respiratory infections and the incidence of diarrhoeal disease.

RESULTS

In Khai Xuan there was a significant reduction (P < 0.0001) in the incidence of respiratory infections (from 49.5% to 11.2%) and diarrhoeal infections (18.3% to 5.1%); the incidence of pneumonia and severe pneumonia was also significantly reduced (P < 0.0001). In Ching Cong there was no significant change in the incidence and severity of respiratory disease nor in the incidence of diarrhoeal disease.

CONCLUSIONS

These findings emphasise the successful health outcome of a nutrition project based on household food production and nutrition education and the value of evaluating nutrition projects by reference to measurable health outcomes.