KRAS Protein Levels Research Articles

The KRAS, ATR and CHEK1 expression levels in endometrial cancer are the risk factors predicting recurrence.

Endometrial cancer is the most prevalent gynecologic malignancy with a high risk of recurrence. Local recurrence occurs in 7-20% of patients with treated stage I cancer within 3 years after primary treatment. In this study, we found significantly elevated mRNA expression levels of the oncoprotein KRAS, along with two replicative stress markers, ATR and CHEK1, in samples of endometrial carcinomas of endometrium (ECE) from patients with relapse. In contrast, mRNA expression levels of the studied genes were low and uniform in samples from patients without relapse. Elevated levels of KRAS protein and the phosphorylated form of ATR/CHEK1 were distinguishing features of recurrent ECE. A strong positive correlation was found between elevated mRNA and protein levels of the studied molecules. Elevated KRAS protein levels are characteristic of poorly differentiated (G3) endometrial carcinomas with deep myometrial invasion in patients without recurrence. In contrast, in patients with recurrence, higher protein levels of KRAS, pATR and pCHEK1 were observed in samples of G1-2 endometrial carcinomas, with statistically significant differences confirmed for pATR. High pCHEK1 protein levels are associated with deep tumor invasion in the myometrium among patients with recurrence. ROC analysis confirmed that evaluating the specificity and sensitivity of KRAS, pATR and pCHEK1 predicts recurrence development in patients with ECE. Our findings indicate that markers of replicative stress may play a significant role in ECE pathogenesis. Determining their levels in tumor samples after primary treatment could help define patients at high risk of recurrence and guide consequent courses of treatment.

Oncogenic mutations of KRAS modulate its turnover by the CUL3/LZTR1 E3 ligase complex.

KRAS is a proto-oncogene encoding a small GTPase. Mutations contribute to ∼30% of human solid tumours, including lung adenocarcinoma, pancreatic, and colorectal carcinomas. Most KRAS activating mutations interfere with GTP hydrolysis, essential for its role as a molecular switch, leading to alterations in their molecular environment and oncogenic signalling. However, the precise signalling cascades these mutations affect are poorly understood. Here, APEX2 proximity labelling was used to profile the molecular environment of WT, G12D, G13D, and Q61H-activating KRAS mutants under starvation and stimulation conditions. Through quantitative proteomics, we demonstrate the presence of known KRAS interactors, including ARAF and LZTR1, which are differentially captured by WT and KRAS mutants. Notably, the KRAS mutations G12D, G13D, and Q61H abrogate their association with LZTR1, thereby affecting turnover. Elucidating the implications of LZTR1-mediated regulation of KRAS protein levels in cancer may offer insights into therapeutic strategies targeting KRAS-driven malignancies.

Intestinal transit-amplifying cells require METTL3 for growth factor signaling and cell survival.

Intestinal epithelial transit-amplifying cells are essential stem progenitors required for intestinal homeostasis, but their rapid proliferation renders them vulnerable to DNA damage from radiation and chemotherapy. Despite these cells' critical roles in intestinal homeostasis and disease, few studies have described genes that are essential to transit-amplifying cell function. We report that RNA methyltransferase-like 3 (METTL3) is required for survival of transit-amplifying cells in the murine small intestine. Transit-amplifying cell death after METTL3 deletion was associated with crypt and villus atrophy, loss of absorptive enterocytes, and uniform wasting and death in METTL3-depleted mice. Sequencing of polysome-bound and methylated RNAs in enteroids and in vivo demonstrated decreased translation of hundreds of methylated transcripts after METTL3 deletion, particularly transcripts involved in growth factor signal transduction such as Kras. Further investigation verified a relationship between METTL3 and Kras methylation and protein levels in vivo. Our study identifies METTL3 as an essential factor supporting the homeostasis of small intestinal tissue via direct maintenance of transit-amplifying cell survival. We highlight the crucial role of RNA modifications in regulating growth factor signaling in the intestine with important implications for both homeostatic tissue renewal and epithelial regeneration.

Abstract 3871: KRAS G12C mutant allele amplification drives resistance to sotorasib in vitro

Abstract Sotorasib is an approved KRASG12C-selective inhibitor for the treatment of KRAS p.G12C-mutant advanced and previously treated non-small cell lung cancers (NSCLC). Acquired resistance due to genomic alterations following sotorasib treatment has been observed in 28% of lung cancer patients (CodeBreaK100, ASCO 2022) and can include bypass signaling, inactivation of negative feedback loops, or compensatory mutations in KRASG12C including amplification of KRAS. Preclinical studies on the mechanisms of acquired resistance are critical for understanding these resistance patterns and can reveal new therapeutic or combination strategies in the clinic. For that reason, we developed an NCI-H358 lung cancer model of acquired resistance to KRASG12C inhibition in vitro. NCI-H358 cells were continuously cultured in the presence of elevated concentrations of sotorasib (IC90) until resistance to KRASG12C inhibitor was achieved. Expression analyses of the resistant cells by ddPCR and immunoblotting showed increases in both KRAS gene and protein levels, resulting in enhanced MAPK signaling. siRNA knockdown of KRAS G12C expression re-sensitized the resistant cells to an analog of sotorasib. Further characterization of this cell line by whole exome sequencing (WES) and fluorescence in situ hybridization (FISH) showed that resistance was not due to genetic co-alterations but amplification of the mutant allele specifically. In comparison to DMSO-treated and parental controls, the sotorasib-resistant NCI-H358 cells contained an approximately 50-fold increase in KRAS G12C mutant allele copy numbers. Preclinical data generated using a KRASG12C inhibitor-resistant lung cancer cell line is consistent with clinical observations of acquired KRAS amplification following KRASG12C inhibitor treatment as a mechanism of resistance. This model further provides an opportunity to study acquired KRAS amplification and investigate combination treatment options in vitro. Citation Format: Deanna Mohn, Anne Y. Saiki, Pragathi Achanta, Andres Plata Stapper, J. Russell Lipford, Rati Verma. KRAS G12C mutant allele amplification drives resistance to sotorasib in vitro. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3871.

Targeting GRP78 suppresses oncogenic KRAS protein expression and reduces viability of cancer cells bearing various KRAS mutations

KRAS is the most commonly mutated oncogene in human cancers with limited therapeutic options, thus there is a critical need to identify novel targets and inhibiting agents. The 78-kDa glucose-regulated protein GRP78, which is upregulated in KRAS cancers, is an essential chaperone and the master regulator of the unfolded protein response (UPR). Following up on our recent discoveries that GRP78 haploinsufficiency suppresses both KRASG12D-driven pancreatic and lung tumorigenesis, we seek to determine the underlying mechanisms. Here, we report that knockdown of GRP78 via siRNA reduced oncogenic KRAS protein level in human lung, colon, and pancreatic cancer cells bearing various KRAS mutations. This effect was at the post-transcriptional level and is independent of proteasomal degradation or autophagy. Moreover, targeting GRP78 via small molecule inhibitors such as HA15 and YUM70 with anti-cancer activities while sparing normal cells significantly suppressed oncogenic KRAS expression in vitro and in vivo, associating with onset of apoptosis and loss of viability in cancer cells bearing various KRAS mutations. Collectively, our studies reveal that GRP78 is a previously unidentified regulator of oncogenic KRAS expression, and, as such, augments the other anti-cancer activities of GRP78 small molecule inhibitors to potentially achieve general, long-term suppression of mutant KRAS-driven tumorigenesis.

KRAS Promoter Methylation Status and miR-18a-3p and miR-143 Expression in Patients With Wild-type KRAS Gene in Colorectal Cancer.

Although some mutations of KRAS proto-oncogene, GTPase (KRAS) have been associated with the prognosis and therapeutic management of colorectal cancer (CRC), the epigenetic mechanisms (DNA methylation and microRNA expression) that regulate wild-type KRAS expression in patients with CRC are poorly known. The aim of this study was to establish whether there is a relationship between the expression of the wild-type KRAS gene, the methylation status of its distal promoter, and miR-143 and miR-18a-3p levels in samples of sporadic CRC. A total of 51 cases of sporadic CRC with wild-type KRAS were analyzed. The expression levels of KRAS mRNA, miR-18a-3p, miR-143, and KRAS protein, as well as methylation in the distal promoter of the KRAS gene were evaluated. In the analyzed cases, KRAS mRNA expression was detected in 51.1%; wild-type KRAS protein was found in the membrane in 31.4% and in the cytoplasm in 98% of cases. An inverse relationship of marginal significance was observed between miR-18a-3p and KRAS protein expression in the cytoplasm (odds ratio=0.14, 95% confidence interval=0.012-1.092; p=0.08). The methylation status of the distal promoter of KRAS at four CpG islands was analyzed in 30 cases (58.8%): partial methylation of the four CpG islands evaluated was observed in two cases (6.7%). In these cases, KRAS protein expression was not evidenced at the membrane level; miR-18a-3p expression was not detected either but high expression of miR-143 was observed. No association was found between the expression levels of KRAS mRNA, miR-18a-3p, miR-143 and methylation status. Methylation status was detected with low frequency, thus being the first report of methylation in wild-type KRAS.

Combination of artesunate and WNT974 induces KRAS protein degradation by upregulating E3 ligase ANACP2 and \u03b2-TrCP in the ubiquitin\u2013proteasome pathway

BackgroundKRAS mutation is one of the dominant gene mutations in colorectal cancer (CRC). Up to present, targeting KRAS for CRC treatment remains a clinical challenge. WNT974 (LGK974) is a porcupine inhibitor that interferes Wnt signaling pathway. Artesunate (ART) is a water-soluble semi-synthetic derivative of artemisinin.MethodsThe synergistic effect of ART and WNT974 combination in reducing CRC cell viability was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. RT-PCR was utilized for the mRNA levels of KRAS, CUL7, ANAPC2, UBE2M, RNF123, SYVN1, or β-TrCP. Western blot assay was utilized for the protein levels of NRAS, HRAS, KRAS, ANAPC2, β-TrCP, GSK-3β, p-Akt (Ser473), t-Akt, p-PI3K (Tyr458), t-PI3K, p-mTOR (Ser2448), t-mTOR. Xenograft mouse model assay was performed for the anti-CRC effect of combination of ART and WNT974 in vivo. IHC assay was utilized for the levels of KRAS, β-TrCP, GSK-3β or ANAPC2 in tumor tissues.ResultsOur study shows that the combination of WNT974 and ART exhibits synergistic effect in reducing CRC growth. The combination treatment significantly reduces KRAS protein level and activity in CRC cells. Interestingly, the combination treatment increases E3 ligases ANAPC2 expression. Our data show that overexpression of ANAPC2 significantly reduces KRAS protein levels, which is reversed by MG132. Knockdown of ANAPC2 in CRC abolishes the combination treatment-reduce KRAS expression. Besides, the treatment also increases the expressions of GSK-3β and E3 ligase β-TrCP that is known to degrade GSK-3β-phosphorylated KRAS protein. Knockdown of β-TrCP- and inhibition of GSK-3β abolish the combination treatment-induce KRAS ubiquitination and reduction in expression. Last but not least, combination treatment suppresses PI3K/Akt/m-TOR signaling pathway.ConclusionsOur data clearly show that the combination treatment significantly enhances KRAS protein degradation via the ubiquitination ubiquitin–proteasome pathway, which is also demonstrated in xenograft mouse model. The study provides strong scientific evidence for the development of the combination of WNT974 and ART as KRAS-targeting therapeutics for CRC treatment.Bh4nRY9p6vgUp6geXci3gHVideo

Effects of K-ras gene silence on the expression of oncogenes in HBE cells treated with PM(2.5)

Objective: To explore the effects of K-ras gene on the expressions of oncogenes and cancer suppressor genes in human bronchial epithelial (HBE) cells which were exposed to PM(2.5). Methods: According to the mRNA sequence of K-ras gene provided by GenBank in September 2019, interference sequences were designed and synthesized, and the recombinant lentiviral vector was transfected into HBE cell to construct the K-ras gene-silenced cells. HBE cells and K-ras gene-silenced cells were exposed to 10 μg/ml, 50 μg/ml PM(2.5) suspension and 10 μmol/L Cr(6+). Real-time fluorescent quantitative PCR was used to detect the mRNA expression levels of c-myc, c-fos, N-ras, cyclin-D1, p16 and p53 genes, the expression levels of p53 and c-myc proteins were detected by Western blot. Results: In K-ras silenced cell group, K-ras mRNA expression level decreased (80.5%±3.6%) and K-ras protein level decreased (58.9%±4.7%) when compared with the control group (P<0.01) . Compared with the correspoding cell control group without exposure, the mRNA expression levels of c-myc, c-fos, N-ras and cyclin-D1 genes in HBE cell group exposed to different concentrations of PM(2.5), K-ras silenced cell group exposed to different concentrations of PM(2.5), HBE cell group exposed to 10 μmol/L Cr(6+) and K-ras silenced cell group exposed to 10 μmol/L Cr(6+) were increased, the mRNA expressions of p16 and p53 genes were decreased (P<0.01) . Compared with HBE cell group exposed to 10 μg/ml PM(2.5), the mRNA expressions of c-myc, c-fos and p16 genes in K-ras silenced cells exposed to 10 μg/ml PM(2.5) were decreased, and the p53 mRNA level was increased (P<0.01) . Compared with HBE cell group exposed to 50 μg/ml PM(2.5), the mRNA expression levels of c-fos, N-ras, cyclin-D1, p16 and p53 genes in K-ras silenced cell group exposed to 50 μg/ml PM(2.5) were decreased (P<0.01) . Compared with the HBE cell group without exposure, c-myc protein increased and p53 protein decreased in HBE cells exposed to 50 μg/ml PM(2.5) (P<0.05) . Compared with the K-ras silenced cell group without exposure, c-myc protein increased in K-ras silenced cells exposed to 50 μg/ml PM(2.5) (P<0.05) . Conclusion: PM(2.5) can increase the expression levels of oncogenes in HBE cells, and K-ras gene silencing can inhibit the expression levels of oncogenes in HBE cells treated with PM(2.5).

MiR-193a-3p Enhanced the Chemosensitivity to Trametinib in Gallbladder Carcinoma by Targeting KRAS and Downregulating ERK Signaling.

Objective: In this study, the authors identified miR-193a-3p as a tumor-suppressing microRNA, and its effects on the chemosensitivity to trametinib in gallbladder carcinoma (GBC) were evaluated. Materials and Methods: The levels of miR-193a-3p in clinical GBC tissues and GBC cells were determined by quantitative real-time polymerase chain reaction. The protein levels of KRAS, ERK, and phosphorylated ERK (p-ERK) were examined by Western blot. Dual-luciferase reporter assays were performed to confirm the interaction between miR-193a-3p and KRAS. The effect of miR-193a-3p knockdown or overexpression on the malignant behaviors and chemosensitivity of GBC was determined by 3-(4,5-dimethlthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide and flow cytometry assays in vitro and further examined in a xenograft model. Results: The levels of miR-193a-3p were significantly decreased in GBC cell lines, especially with KRAS mutations. In addition, miR-193a-3p overexpression retarded cell proliferation of GBC, but induced cell apoptosis. Moreover, miR-193a-3p overexpression significantly improved the chemosensitivity of GBC to trametinib both in in vitro assays and in vivo xenograft mouse model. Further mechanisms disclosed that KRAS was a target of miR-193a-3p and levels of p-ERK were increased by treatment with miR-193a-3p inhibitor in GBC. Conclusions: These data suggested that miR-193a-3p enhanced the chemosensitivity to trametinib in GBC with wild-type KRAS or KRAS mutations by directly targeting KRAS and finally downregulated ERK signaling.

Abstract 2130: Association between miR-18a-3p, miR-143 and expression of the wild-type KRAS gene in patients with sporadic colorectal cancer

Abstract Introduction: Colorectal cancer (CRC) has the third-highest incidence and the fourth-highest mortality from cancer globally. In the genesis of CRC, mutations have been identified in the KRAS gene associated with prognosis and therapeutic management, however, the epigenetic mechanisms that modulate the expression of KRAS in CRC patients when there are no mutations in the gene are not well known. miR-18a-3p and miR-143 have been described to target KRAS and thus may regulate gene expression. Objective: To determine if there is a relationship between the expression of the wild-type KRAS gene (mRNA and protein) and the expression levels of miR-143 and miR-18a-3p in FFPE tissue samples from CRC patients. Methodology: RNA was extracted from FFPE tumor tissue samples from 51 cases of patients with CRC. Expression of wild-type KRAS mRNA, miR-143 and miR-18a-3p was evaluated by qRT-PCR and expression levels of KRAS protein by immunohistochemistry. Contingency tables, Pearson's Chi-square test and logistic regression analysis were used for data analysis. Results: Regarding the expression levels of wild-type KRAS protein, a higher number of cases with a cytoplasmic expression of the protein was identified (98%) compared to the expression in the cell membrane (31%). In 7,8% (4/51) of the cases, it was not possible to determine the mRNA expression of the KRAS gene, while in 21,3% (10/47) no expression was detected. In 78,7% of the cases in which KRAS mRNA expression was detected, low (40,4%; 19/47) and high (38,3%; 18/47) expression were categorized according to the results found. It was not evidenced by a correlation between protein expression levels and mRNA expression levels of the wild-type KRAS gene. When determining the expression levels of miR-18a-3p and miR-143, it was found that 64,7% (33/51) of cases had an absent expression of miR-18a-3p and 54,9% (28/51) of cases had an absent or very low expression for miR-143. By means of a logistic regression analysis adjusted by age, stage, sex and presence or absence of KRAS protein in the membrane, it was determined that the presence of miR-18a-3p is inversely related to KRAS mRNA levels significantly (p=0,048; OR=0,346) while miR-143 only shows a tendency to an inverse correlation with KRAS mRNA levels (p=0,119; OR=0,469). Conclusions: No correlation was found between mRNA and protein expression levels of the wild-type KRAS gene, suggesting that protein levels do not strictly depend on mRNA levels. A significant inverse association was found between miR-18a-3p and wild-type KRAS mRNA levels. Citation Format: Jehison-Alirio Herrera-Pulido, Orlando Ricaurte Guerrero, Jinneth Acosta Forero, Gustavo Hernández Suárez, Pablo Moreno-Acosta, María-Carolina Sanabria Salas, Humberto Arboleda Granados, Alfredo Romero Rojas, Martha Lucía Serrano López. Association between miR-18a-3p, miR-143 and expression of the wild-type KRAS gene in patients with sporadic colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2130.

Abstract 2936: Ago2 induces Kras signaling and promotes tumor progression in mouse models of lung adenocarcinoma

Abstract Lung cancer is the deadliest malignancy in the United States. Non-small cell lung cancer (NSCLC) accounts for 85% of cases, and is frequently driven by activating mutations in the gene encoding the KRAS GTPase (e.g. KRASG12D). Our previous work demonstrated that Argonaute 2 (AGO2)—a component of the RNA induced silencing complex (RISC)—physically interacts with KRAS and stabilizes it at the protein level. In multiple cell lines, AGO2 knockdown reduces KRAS protein level and attenuates cell proliferation. We therefore hypothesized that AGO2 could promote KRASG12D-dependent NSCLC in vivo. To test the hypothesis, we evaluated the impact of Ago2 knockout in the KPC mouse model of NSCLC. In KPC mice, intratracheal delivery of adenoviral Cre drives lung-specific expression of a stop-floxed KRASG12D allele and biallelic ablation of p53. Simultaneous biallelic ablation of floxed Ago2 inhibited KPC lung nodule growth while reducing proliferative index and improving pathological grade. We next applied the KPHetC model, in which the clara cell-specific CCSP-driven Cre activates KRASG12D and ablates a single p53 allele. In these mice, Ago2 ablation also reduced tumor size and grade. In both models, Ago2 knockout inhibited ERK phosphorylation in tumor nodules, indicating impaired KRAS signaling. Furthermore, RNA-seq analysis of KPC nodules demonstrated broadly reduced expression of Kras-related genes. Taken together, our data demonstrate a novel pathogenic role for AGO2 in KRAS-dependent NSCLC. Given the prevalence of this malignancy and current difficulties in therapeutically targeting KRAS signaling, our work has future translational relevance. Citation Format: Jean C. Tien, Seema Chugh, Andrew E. Goodrum, Yunhui Cheng, Lisha Wang, Rahul Mannan, Xiaoming Wang, Vijaya L. Dommeti, Yuping Zhang, Alice Xu, Fengyu Su, Xuhong Cao, Sunita Shankar, Arul M. Chinnaiyan. Ago2 induces Kras signaling and promotes tumor progression in mouse models of lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2936.

Abstract 2273: MAPK signaling pathway disruption explains the anticancer mechanism for polyisoprenylated cysteinyl amide inhibitors (PCAIs)

Abstract The Mitogen-activated protein kinase (MAPK) pathway is one of the key signaling pathways that regulates normal cell proliferation, differentiation, and survival. Abnormalities of the pathway play vital roles in cancer initiation and progression. Ras small GTPases that are key upstream mediators of the MAPK pathway are mutated in 20%-30% of human tumors. KRAS is the most frequently mutated isoform of the RAS proteins, accounting for up to 86% of RAS mutant cancer cases. Mutant KRAS is prevalent in lung, colon, and pancreatic cancers, which considered to be the most aggressive and account for the most cancer deaths in the US. To help mitigate this problem and fill the therapeutic need that has lingered for decades, polyisoprenylated cysteinyl amide inhibitors (PCAIs) were designed and synthesized to target the hyperactivity of aberrant monomeric G-Proteins. Recently, the PCAIs underwent a synthetic optimization to mitigate the excessive hydrophobicity of the earlier analogs. While the newer agents are more polar and have maintained the effectiveness of the earlier PCAIs against cancer cell lines driven by mutant KRAS proteins, the specific anticancer mechanisms are still unclear. Thus, we explored the effects of the newer PCAIs on the MAPK pathway using lung cancer A549 cells which harbor the KRAS mutation. When the cells were treated with NSL-YHJ-2-27 for 48 h, the KRAS protein levels dropped by 40% at 5μM compared to the controls. However, no significant difference was observed in the levels of total or phosphorylated B- and C-Raf proteins. Moreover, it was observed that the PCAIs immensely stimulated the MAPK pathway in a concentration-dependent manner following treatment with 1, 2, and 5μM of NSL-YHJ-2-27. The phosphorylation of MEK1/2, ERK1/2, and p90RSK significantly increased by 84%, 59%, and 160%, respectively, relative to controls following treatment for 48h at 5 µM of NSL-YHJ-2-27. Interestingly, a non-farnesylated analog, NSL-YHJ-2-62, did not elicit similar effects on the MAPK pathway. Although ERK stimulation has mostly been associated with cell survival and proliferation, various studies show that ERK activation can also mediate apoptosis depending on the intensity and duration of the stimulation. These data reveal that the Ras-MAPK signaling axis is involved in the anticancer effects of the PCAIs. The PCAIs may thus be considered as possible agents for the unmet therapeutic needs of patients with aberrantly hyperactive G-proteins. Citation Format: Nada Tawfeeq, Yonghao Jin, Nazarius Lamango. MAPK signaling pathway disruption explains the anticancer mechanism for polyisoprenylated cysteinyl amide inhibitors (PCAIs) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2273.

Abstract 1955: Inhibition of eIF4A by eFT226 blocks KRAS mutant tumor growth

Abstract Mutations in KRAS are among the most common oncogenic lesions across a variety of human cancers. Activation of KRAS directs signaling via the MAPK and PI3K pathways to promote tumor growth. One outcome of enhanced KRAS signaling is the induction of mRNA translation by eIF4A, eIF4E, and eIF4G, which together comprise the eIF4F complex. eIF4A is an RNA helicase that functions to unwind elements in the 5'-untranslated region (UTR) of mRNAs to facilitate scanning of the 40S ribosomal subunit. eFT226 is a highly potent and selective inhibitor of eIF4A that functions by forming a ternary complex between eIF4A, eFT226 and specific polypurine motifs in the 5'-UTR of select mRNAs, thus blocking ribosome scanning and inhibiting mRNA translation. This polypurine sequence motif is highly enriched in the 5'-UTR of eFT226 target genes, many of which are known proto-oncogenes. Translational profiling revealed KRAS to be a target of eFT226 and 5'-UTR sequence analysis of KRAS mRNA identified the polypurine regulatory motif, which imparts sensitivity to eFT226 mediated inhibition of translation. In cell-based reporter assays used to monitor translation, mutation of the KRAS 5'-UTR polypurine motifs resulted in a 10-fold decrease in sensitivity to eFT226 relative to the wild-type sequence. In a cell panel screen for in vitro apoptosis induction by eFT226, the most sensitive models were enriched for cell lines driven by KRAS mutations. Consistent with these results, treatment with eFT226 decreased KRAS protein levels, repressed downstream MAPK signaling, inhibited cell proliferation, and induced apoptosis in a collection of non-small cell lung, colorectal and pancreatic KRAS mutant cancer cell lines. The ability of eFT226 to block tumor cell growth and induce apoptosis is independent of the specific KRAS mutation present (e.g. G12C/V, G13D, Q61H/L) suggesting that eFT226 could be broadly efficacious in treating tumors with activating KRAS mutations. Treatment of KRAS mutant solid tumor xenografts with eFT226 as a monotherapy significantly inhibited tumor growth. Together, these results highlight the ability of eFT226 to inhibit growth and promote apoptosis in KRAS mutant tumors and support the clinical development of eFT226 in KRAS driven tumors. A clinical trial evaluating eFT226 in patients with solid tumor malignancies has initiated. Citation Format: Craig R. Stumpf, Vikas K. Goel, Joan Chen, Jocelyn Staunton, Emily M. Santori, Maria Barrera, Haleigh Howard, Kevin R. Webster, Gary G. Chiang, Peggy A. Thompson. Inhibition of eIF4A by eFT226 blocks KRAS mutant tumor growth [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1955.

Abstract B32: Silencing of oncogenic KRAS by a mutant-favoring short interfering RNA

Abstract Oncogenic mutations in the KRAS gene are well-established drivers of cancer. Promising preclinical strategies including RNA interference (RNAi) have been developed to target oncogenic KRAS function, yet a clinically effective therapy to directly target KRAS remains to be achieved. While genetic knockdown of mutant KRAS (mKRAS) with RNAi is one promising approach, current methods are not mutant-selective, and thus they also decrease normal KRAS levels, raising concerns about normal cell toxicity. Here, we describe a custom short interfering RNA (siRNA) oligonucleotide (D1) designed to preferentially bind the most commonly occurring RAS missense mutations in codons 12 and 13. Our approach designed the siRNA to have three mismatches binding wild-type mRNA, but only two mismatches for the oncogenic mRNAs, thus having binding affinities more favorable for the mutant-specific sequences. Using NIH/3T3 mouse fibroblasts stably expressing human KRAS WT or mutant cDNA sequences and KRAS mutant lung cancer cell lines, we determined that D1 siRNA preferentially reduced mKRAS mRNAs versus the wild-type sequence at the transcriptional and protein levels. Phenotypically, D1 siRNA significantly reversed mKRAS-induced morphologic and growth transformation of NIH/3T3 cells. Furthermore, D1 siRNA significantly impaired the proliferation of several mKRAS lung cancer cells in 2D as well as 3D spheroids embedded in an extracellular matrix. To overcome clinical limitations of delivering the siRNA to lung tumors, we evaluated lipid nanoparticles (LNPs) as carriers of D1 siRNAs in orthotopic mKRAS lung cancer models and observed that Cy5.5-labeled LNPs are highly enriched in lung tumors and metastases. Compared with control siRNA-LNP treated mice, 344SQ (KRAS G12D) tumor-bearing mice injected once with D1 siRNA-LNPs had drastically decreased KRAS protein levels in tumors 72 h later (73% decrease, p=0.001). Using an orthotopically injected luciferase-labeled A549 (KRAS G12S) human lung cancer model, D1 siRNA-LNP treated mice had pronounced reductions in luciferase signal (56% reduction, p=0.045), chest wall metastases (67% reduction, p&amp;lt;0.001) and contralateral lung metastases (73% reduction, p&amp;lt;0.01). Interestingly, D1 siRNA-LNP did not impair tumor growth when applied in the 344SQ mKRAS orthotopic mouse lung model, consistent with the mKRAS-independent growth of this line. This result supports our conclusion that the effects of D1 siRNA-LNP in the A549 model are KRAS specific and highlight the importance of determining RAS-dependency a priori for KRAS-targeting therapeutics. Taken together, our data indicate a novel use of RNAi to specifically target oncogenic KRAS-driven cancers. Citation Format: Bjoern Papke, Amanda E.D. Van Swearingen, Anne Y. Feng, Salma H. Azam, Emily B. Harrison, Runying Yang, Adrienne D. Cox, Channing J. Der, Chad V. Pecot. Silencing of oncogenic KRAS by a mutant-favoring short interfering RNA [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 B32.

Polyisoprenylated Cysteinyl Amide Inhibitors Deplete K-Ras and Induce Caspase-dependent Apoptosis in Lung Cancer Cells.

Non-small cell lung cancers (NSCLC) harboring mutation-induced dysregulation of Ras signaling present some of the most difficult-to-manage cases, since directly targeting the constitutively active mutant Ras proteins has not resulted in clinically useful drugs. Therefore, modulating Ras activity for targeted treatment of cancer remains an urgent healthcare need. In the current study, we investigated a novel class of compounds, the polyisoprenylated cysteinyl amide inhibitors (PCAIs), for their anticancer molecular mechanisms using the NSCLC cell panel with K-Ras and/or other mutant genes. The effect of the PCAIs on intracellular K-Ras levels, cell viability, apoptosis, spheroid and colony formation were determined. Treatment of the lung cancer cells with the PCAIs, NSL-RD-035, NSL-BA-036, NSL-BA- 040 and NSL-BA-055 resulted in concentration-dependent cell death in both K-Ras mutant (A549, NCI-H460, and NCI-H1573), N-Ras mutant (NCI-H1299) and other (NCI-H661, NCI-H1975, NCIH1563) NSCLC cells. The PCAIs at 1.0 -10 μM induced the degeneration of 3D spheroid cultures, inhibited clonogenic cell growth and induced marked apoptosis via the extrinsic pathway. The most potent of the PCAIs, NSL-BA-055, at 5 μM induced a seven-fold increase in the activity of caspase- 3/7 and a 75% selective depletion of K-Ras protein levels relative to GAPDH in A549 cells that correlated with PCAIs-induced apoptosis. NSL-BA-040 and NSL-BA-055 also induced the phosphorylation of MAP kinase (ERK 1/2). Taken together, PCAIs may be potentially useful as targeted therapies that suppress NSCLC progression through disruption of Ras-mediated growth signaling.

Downregulation of miR‑143 modulates KRAS expression in colorectal carcinoma cells.

MicroRNAs (miRs) are a class of non‑coding small RNAs that have been demonstrated to be involved in the pathogenesis of human cancer. There is even evidence that microRNAs can act as oncogenes or tumor suppressors. Although microRNA expression profiles have been characterized in colorectal carcinoma, their precise physiological functions are largely unknown. It has become clear that the activated KRAS Proto‑Oncogene, GTPase (KRAS) oncogene plays an important role in colorectal carcinogenesis. In the present study, it was found that the level of mature miR‑143 was lower in colorectal carcinoma tissues compared with that observed in normal adjacent tissues. A lack of miR‑143 was detected in human colorectal carcinoma cell lines, SW480, LoVo and HT‑29, compared to the high expression observed in normal colon epithelial cell line NCM460. pcDNA3.1‑pri‑miR‑143 and its mutant were successfully constructed and transfected into colorectal carcinoma cells. Increased accumulation of mature miR‑143 was observed in the pcDNA3.1‑pri‑miR‑143‑transfected cells. In SW480 cells, transfection of pcDNA3.1‑pri‑miR‑143 resulted in a 35 and 47% reduction in cell growth after incubation for 4 and 5 days, respectively, compared with transfection of the pcDNA3.1‑pri‑miR‑143 mutant; while in LoVo cells, transfection of pcDNA3.1‑pri‑miR‑143 resulted in a 33 and 46% reduction in cell growth respectively. In contrast, transfection of pcDNA3.1‑pri‑miR‑143 had no significantly effects on HT‑29 cell growth. We also found that transfection of pcDNA3.1‑pri‑miR‑143 had no effect on levels of KRAS mRNA, but resulted in a 58% decrease in the KRAS protein level in the transfected SW480 cells, while an approximate 54 and 43% KRAS protein reduction in LoVo and HT‑29 cells, respectively, compared with the pcDNA3.1‑pri‑miR‑143 mutant. Two fragments containing the putative complementary site were cloned into the pGL3 vector, constructing the luciferase reporter pGL3‑KRAS‑CS1 and pGL3‑KRAS‑CS2. Cotransfection of pcDNA3.1‑pri‑miR‑143 with pGL3‑KRAS‑CS1 and pGL3‑KRAS‑CS2 respectively resulted in 4.6‑ and 3.3‑fold inhibition of luciferase activity in the SW480 cells, while a 4.0‑ and 3.2‑fold inhibition of luciferase activity in the LoVo cells, 3.7‑ and 3.1‑fold inhibition in the HT‑29 cells. Differences in pGL3‑KRAS‑CS1 and pGL3‑KRAS‑CS2 activity were not significant. Our results revealed that increased accumulation of miR‑143 is likely to modulate levels of KRAS protein expression at the post‑transcriptional level by interacting specifically with the complementary site, and consequently inhibiting proliferation of the transfected cells.

Ribosome profiling analysis identified a KRAS-interacting microprotein that represses oncogenic signaling in hepatocellular carcinoma cells.

The roles of concealed microproteins encoded by long noncoding RNAs (lncRNAs) are gradually being exposed, but their functions in tumorigenesis are still largely unclear. Here, we identify and characterize a conserved 99-amino acid microprotein named KRASIM that is encoded by the putative lncRNA NCBP2-AS2. KRASIM is differentially expressed in normal hepatocytes and hepatocellular carcinoma (HCC) cells and can suppress HCC cell growth and proliferation. Mechanistically, KRASIM interacts and colocalizes with the KRAS protein in the cytoplasm of human HuH-7 hepatoma cells. More importantly, the overexpression of KRASIM decreases the KRAS protein level, leading to the inhibition of ERK signaling activity in HCC cells. These results demonstrate a novel microprotein repressor of the KRAS pathway for the first time and provide new insights into the regulatory mechanisms of oncogenic signaling and HCC therapy.

Arsenic Alters Exosome Quantity and Cargo to Mediate Stem Cell Recruitment Into a Cancer Stem Cell-Like Phenotype.

Inorganic arsenic is a human carcinogen that can target the prostate. Accumulating evidence suggests arsenic can disrupt stem cell (SC) dynamics during the carcinogenic process. Previous work demonstrated arsenic-transformed prostate epithelial (CAsE-PE) cells can recruit prostate SCs into rapidly acquiring a cancer SC (CSC) phenotype via the secretion of soluble factors. Exosomes are small, membrane-derived vesicles that contain lipids, RNA, and proteins, and actively contribute to cancer initiation and progression when taken up by target cells. Here we hypothesized that CAsE-PE cells are recruiting SCs to a CSC-like phenotype via exosomal signaling. CAsE-PE cells secreted 700% more exosomes than parental RWPE-1 cells. CAsE-PE exosomes were enriched with oncogenic factors, including oncogenes (KRAS, NRAS, VEFGA, MYB, and EGFR), inflammation-related (cyclooxygenase-2, interleukin 1B (IL1B), IL6, transforming growth factor-β, and tumor necrosis factor-A), and apoptosis-related (CASP7, CASP9, and BCL2) transcripts, and oncogenesis-associated microRNAs. When compared with SCs cultured in exosome-depleted conditioned medium (CM), SCs cultured in CM containing CAsE-PE-derived exosomes showed increased (198%) matrix metalloproteinase activity and underwent an epithelial-to-mesenchymal transition in morphology, suggesting an exosome-mediated transformation. KRAS plays an important role in arsenic carcinogenesis. Although KRAS transcript (>24 000%) and protein (866%) levels were elevated in CAsE-PE exosomes, knock-down of KRAS in these cells only partially mitigated the CSC-like phenotype in cocultured SCs. Collectively, these results suggest arsenic impacts both exosomal quantity and cargo. Exosomal KRAS is only minimally involved in this recruitment, and additional factors (eg, cancer-associated miRNAs) likely also play a role. This work furthers our mechanistic understanding of how arsenic disrupts SC dynamics and influences the tumor microenvironment during carcinogenesis.

Abstract 1449: Aberrant expression of protein kinase D1 influences metabolic reconditioning in pancreatic cancer

Abstract Objective: Pancreatic cancer is one of the deadliest diseases, and the fourth most common cause of cancer-related deaths in the United States. Protein Kinase D1 (PKD1), a serine-threonine kinase, is an important modulator of several kinase signal transduction pathways. Although, PKD1 is known to be involved in pancreatic cancer pathogenesis, the underlying signaling mechanisms are largely unknown. Therefore, we investigated how PKD1 contributes to pancreatic tumor growth and progression. Our studies suggest a novel role of PKD1 in regulating glucose metabolism in pancreatic cancer, which drives pancreatic tumorigenesis and progression. Methods: Glucose and Lactate assays were performed in pancreatic cancer cells following PKD1 transfection. Cell culture media was collected after 48 hrs to measure the amount of glucose consumption and L-lactate production on PKD1 expression in pancreatic cancer cells using in vitro assay kits (Cayman Chemicals). Immunoblotting and qRT-PCR assays were performed to assess the expression of protein and mRNA levels, respectively, of key signaling molecules in glucose metabolism in pancreatic cancer cells. Cell proliferation and colony forming assays were performed to determine the effect of PKD1 on cell proliferation and survival under both normoxic and hypoxic conditions. In vitro functional assays for investigating migration and invasion were performed using boyden chamber and Matrigel assays, respectively, under normoxic and hypoxic conditions. Results: Our results show that PKD1 leads to altered glucose metabolism in pancreatic cancer cells. We observed increased amount of L-lactate production and glucose consumption on PKD1 expression in cells. This indicates the alterations in glucose metabolism associated with PKD1 expression in cells. These alterations were accompanied with enhanced expression of both protein and mRNA levels of Glut-1, HIF-1α, and KRAS, which are associated with glucose metabolism. These events were observed in both normoxic and hypoxic conditions, indicating that the PKD1 modulated events are independent of oxygen tension. Furthermore, we observed enhanced invasion and migration of pancreatic cancer cells on PKD1 expression, which was further increased by addition of lactate (an end product of aerobic glycolysis). Altogether, our studies indicate a role of PKD1 as a key regulator of the glucose metabolism and promoter of pancreatic cancer oncogenesis. Conclusion: These results suggest that PKD1 plays an important role in metabolic reprogramming of pancreatic cancer cell metabolism to induce cancer growth and enhanced cellular invasion and motility. This is a first study that suggests the involvement of PKD1 in metabolic remodeling of pancreatic cancer cells leading to enhanced tumor growth and progression. Citation Format: Sonam Kumari, Sheema Khan, Murali M. Yallapu, Subhash C. Chauhan, Meena Jaggi. Aberrant expression of protein kinase D1 influences metabolic reconditioning in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1449.

Abstract 5099: Evaluating Ago2 as an oncogene in Kras-dependent lung carcinoma

Abstract Background: Lung cancer is the deadliest malignancy in the United States. Non-small cell lung cancer (NSCLC) accounts for 85% of cases, and is frequently driven by activating mutations in the gene encoding the KRAS GTPase (e.g. KRASG12D). Our previous work demonstrated that Argonaute 2 (AGO2)—a component of the RNA induced silencing complex (RISC)—physically interacts with KRAS and stabilizes it at the protein level. In NSCLC cell lines, AGO2 knockdown reduces KRAS protein level and attenuates cell proliferation. We hypothesized that AGO2 acts as an oncogene in KRASG12D-dependent NSCLC in vivo. Methods: To test the hypothesis, we generated a NSCLC model by intercrossing mice harboring a stop-floxed KRASG12D allele with animals containing a tamoxifen-responsive Cre recombinase gene driven by the (clara cell-specific) CCSP promoter. These animals, which frequently die within 10 weeks of tamoxifen treatment, display pulmonary lesions including hyperplasia, adenoma and frank adenocarcinoma. We evaluated whether concomitant ablation of one or both copies of (floxed) AGO2 influenced the NSCLC phenotype. After tamoxifen administration, we monitored mice daily and harvested tissues when mice were clinically moribund or reached 16 weeks of post-treatment. We harvested lungs for gross/ pathological examination and gene/ protein expression analysis. Results: While pathologically discernable adenocarcinoma was detectable in AGO2+/+ and AGO2f/+ animals, AGO2f/f mice were free of these lesions. Despite this, deletion of AGO2 had no impact on frequency or extent of hyperplastic or adenomatous lesions. Immunohistochemistry demonstrated absence of AGO2 in tumor tissue of AGO2f/f mice. Conclusion: AGO2 promotes progression but not initiation of cancerous lesions in a mouse model of KRASG12D-dependent NSCLC. Citation Format: Andrew E. Goodrum, Lisha Wang, Alice Xu, Kristin M. Juckette, Arul M. Chinnaiyan, Jean C. Tien. Evaluating Ago2 as an oncogene in Kras-dependent lung carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5099.