KRAS allel-specific activity of sunitinib in an isogenic disease model of colorectal cancer

Actionability classification of variants of unknown significance correlates with functional effect

Genomically-informed therapy requires consideration of the functional impact of genomic alterations on protein expression and/or function. However, a substantial number of variants are of unknown significance (VUS). The MD Anderson Precision Oncology Decision Support (PODS) team developed an actionability classification scheme that categorizes VUS as either "Unknown" or "Potentially" actionable based on their location within functional domains and/or proximity to known oncogenic variants. We then compared PODS VUS actionability classification with results from a functional genomics platform consisting of mutant generation and cell viability assays. 106 (24%) of 438 VUS in 20 actionable genes were classified as oncogenic in functional assays. Variants categorized by PODS as Potentially actionable (N = 204) were more likely to be oncogenic than those categorized as Unknown (N = 230) (37% vs 13%, p = 4.08e-09). Our results demonstrate that rule-based actionability classification of VUS can identify patients more likely to have actionable variants for consideration with genomically-matched therapy.

Mammary mucinous cystadenocarcinoma with long-term follow-up: molecular information and literature review

BACKGROUND

Mucinous cystadenocarcinoma (MCA) is a very rare form of breast cancer that was first described in 1998. Only 33 cases of primary MCA, including our present case, have been reported thus far. As a consequence, its molecular features, prognosis and treatment regimen are poorly known. Here, we describe a less common presentation of MCA, detail its molecular features, discuss the major differential diagnosis, and provide a brief review of the literature.

CASE PRESENTATION

A 59-year-old woman presented with a breast lump in which mammography showed a well-defined nodule. Core needle biopsy (CNB) revealed several lesions lined by tall columnar cells with stratification and abundant mucinous secretion; excision was recommended for final diagnosis. The resected specimens showed cavities of different sizes without surrounding myoepithelial cells. The cavities were rich in mucus, and the nuclei were located at the base of the cells, containing intracellular mucus. Immunohistochemical analysis revealed that it was triple-negative breast cancer (TNBC). Next-generation sequencing (NGS) revealed pathogenic mutations in the PIK3CA, KRAS, MAP2K4, RB1, KDR, PKHD1, TERT, and TP53 genes. A diagnosis of MCA was rendered. The patient has been followed up for 108 months to date and showed no signs of recurrence or metastasis.

CONCLUSION

Our study presents the gene profile of an MCA case with no recurrence or metastatic tendency after 108 months of follow-up, and a review of the literature helps us better understand the clinical, pathologic, and molecular features of this tumor.

ZEB1 directly inhibits GPX4 transcription contributing to ROS accumulation in breast cancer cells

PURPOSE

Prior studies have noted that zinc finger E-box binding homeobox 1 (ZEB1) is a master transcription regulator, affecting the expression of nearly 2000 genes in breast cancer cells, especially in the epithelial-mesenchymal transition (EMT) process. We now tested the role of ZEB1 on the oxidative stress of cancer cells and explored its possible mechanisms.

METHODS

Two human breast cancer cell lines MDA-MB-231 and MCF7 were selected for the ROS test, PCR, immunofluorescence, Western blot, chromatin immunoprecipitation assay, luciferase assay, and enzyme assay. Mouse models experiments and bioinformatics analysis were conducted to test the indicated molecules.

RESULTS

We observed ZEB1 could inhibit GPX4 transcription by binding to the E-box motifs and promote breast cancer progression by accumulating intracellular ROS. From the perspective of ROS clearance, Vitamin E enhanced GPX4 function to consume L-glutathione and eliminated excess intracellular ROS.

CONCLUSIONS

ZEB1 could not only regulate EMT, but also inhibit GPX4 transcription by binding to the E-box motif. It was important to note that the ZEB1/GPX4 axis had a therapeutic effect on breast cancer metabolism.

Mutation-Specific and Common Phosphotyrosine Signatures of KRAS G12D and G13D Alleles

KRAS is one of the most frequently mutated genes across all cancer subtypes. Two of the most frequent oncogenic KRAS mutations observed in patients result in glycine to aspartic acid substitution at either codon 12 (G12D) or 13 (G13D). Although the biochemical differences between these two predominant mutations are not fully understood, distinct clinical features of the resulting tumors suggest involvement of disparate signaling mechanisms. When we compared the global phosphotyrosine proteomic profiles of isogenic colorectal cancer cell lines bearing either G12D or G13D KRAS mutation, we observed both shared as well as unique signaling events induced by the two KRAS mutations. Remarkably, while the G12D mutation led to an increase in membrane proximal and adherens junction signaling, the G13D mutation led to activation of signaling molecules such as nonreceptor tyrosine kinases, MAPK kinases, and regulators of metabolic processes. The importance of one of the cell surface molecules, MPZL1, which was found to be hyperphosphorylated in G12D cells, was confirmed by cellular assays as its knockdown led to a decrease in proliferation of G12D but not G13D expressing cells. Overall, our study reveals important signaling differences across two common KRAS mutations and highlights the utility of our approach to systematically dissect subtle differences between related oncogenic mutants and potentially lead to individualized treatments.

KRAS and BRAF Concomitant Mutations in a Patient with Metastatic Colon Adenocarcinoma: An Interesting Case Report

A 68-year-old female patient with tenesmus and blood in the stool was admitted to the S.G. Moscati Hospital of Taranto. Investigations revealed infiltrative mucinous colon adenocarcinoma accompanied by lymph node metastases. Following surgery and adjuvant chemotherapy, computed tomography (CT) and carcinoembryonic antigen screening were negative. Two years later, CT demonstrated a liver lesion. Histologic and genetic analyses confirmed the diagnosis of metastatic colorectal cancer with the coexistence of KRAS and BRAF mutations in hepatic metastases and the presence of the BRAF V600E in the primary tumour. It is unclear whether the lack of response was due to BRAF mutations, but the data suggest that mutated BRAF confers resistance to anti-epidermal growth factor receptor therapy. In our patient, BRAF mutation turned out to be a negative prognostic factor, and it may have been the cause of clinical implications for disease progression and therapeutic responses.

Concomitant KRAS and BRAF mutations in colorectal cancer

BRAF and KRAS are two key oncogenes in the RAS/RAF/MEK/MAP-kinase signaling pathway. While previously considered mutually exclusive, concomitant mutations in both KRAS and BRAF genes have been identified in colorectal cancer (CRC). The clinical outcome of these patients remains undetermined. We present the clinical course of two patients with CRC harboring mutations at codon 12 of KRAS and BRAF non-V600E mutations. More research is needed to determine the clinical-pathological effect of these simultaneous mutations of KRAS and BRAF in CRC on disease course and treatment outcome.

Molecular subtype specific efficacy of MEK inhibitors in pancreatic cancers

Pancreatic cancer is an increasing cause of cancer related death worldwide. KRAS is the dominant oncogene in this cancer type and molecular rationale would indicate, that inhibitors of the downstream target MEK could be appropriate targeted agents, but clinical trials have failed so far to achieve statistically significant benefit in unselected patients. We aimed to identify predictive molecular biomarkers that can help to define subgroups where MEK inhibitors might be beneficial alone or in combination. Next-generation sequencing data of 50 genes in three pancreatic cancer cell lines (MiaPaCa2, BxPC3 and Panc1) were analyzed and compared to the molecular profile of 138 clinical pancreatic cancer samples to identify the molecular subtypes of pancreatic cancer these cell lines represent. Luminescent cell viability assay was used to determine the sensitivity of cell lines to kinase inhibitors. Western blot was used to analyze the pathway activity of the examined cell lines. According to our cell viability and pathway activity data on these model cell lines only cells harboring the rare G12C KRAS mutation and low EGFR expression are sensitive to single MEK inhibitor (trametinib) treatment. The common G12D KRAS mutation leads to elevated baseline Akt activity, thus treatment with single MEK inhibitors fails. However, combination of MEK and Akt inhibitors are synergistic in this case. In case of wild-type KRAS and high EGFR expression MEK inhibitor induced Akt phosphorylation leads to trametinib resistance which necessitates for MEK and EGFR or Akt inhibitor combination treatment. In all we provide strong preclinical rational and possible molecular mechanism to revisit MEK inhibitor therapy in pancreatic cancer in both monotherapy and combination, based on molecular profile analysis of pancreatic cancer samples and cell lines. According to our most remarkable finding, a small subgroup of patients with G12C KRAS mutation may still benefit from MEK inhibitor monotherapy.

Effect of KRAS exon 2 mutations on antitumor activity of afatinib and gefitinib

The aim of this study was to investigate the impact of different KRAS mutations on the inhibitory potential of afatinib and gefitinib in SW48 colorectal cancer cells. The influence of afatinib/gefitinib on cell viability and cell cycle was evaluated in isogenic SW48 KRAS wild-type/mutant cells. Protein levels of phosphorylated/total EGFR, HER-2, HER-3, ERK, and AKT were compared between treated/untreated samples using western blotting. The activity of both afatinib and gefitinib was the lowest in KRAS G12C/G12S/G12D and the highest in G13D/G12A mutant subtypes. A 50% decrease in cell viability was achieved at concentrations of 3.0-7.7 μmol/l for afatinib and 5.4-19.5 μmol/l for gefitinib. The effect of both drugs on apoptosis appeared to be stronger than their influence on proliferation and was generally less pronounced in mutant cells than in wild-type cells. The average number of apoptotic cells after treatment with afatinib was 2.6 times as high as the corresponding value following treatment with gefitinib (P<0.01). Levels of pEGFR, pHER-2, pERK, and pAKT were reduced more extensively by afatinib than by gefitinib (P<0.001). Some KRAS mutations (G12C/G12S/G12D) appear to weaken the activity of afatinib and gefitinib whereas others seem to increase sensitivity to treatment (G13D/G12A) compared with the parental clone (KRAS wild-type). In SW48 colorectal cancer cells, afatinib seems to be more potent than gefitinib because of its superior efficacy in inhibiting both EGFR and HER-2, suppressing signaling along both MEK/ERK and PI3K/AKT pathways to a greater extent.

KRAS exon 2 mutations influence activity of regorafenib in an SW48-based disease model of colorectal cancer

ABSTRACT 

Aim: To investigate the impact of KRAS mutation variants on the activity of regorafenib in SW48 colorectal cancer cells. Materials & methods: Activity of regorafenib was evaluated in isogenic SW48 KRAS wild-type (WT) and mutant cells. Subcutaneous xenografts (KRAS WT and G12C mutant variants) in NOD/SCID mice were analyzed to elucidate the effect of regorafenib treatment in vivo. Results: Compared with KRAS WT cells, all mutant variants seemed associated with some degree of resistance to regorafenib-treatment in vitro. In vivo, activation of apoptosis (TUNEL) and reduction of proliferation (Ki67) after treatment with regorafenib were more pronounced in KRAS WT tumors as compared with G12C variants. Conclusion: In SW48 cells, exon 2 mutations of the KRAS gene may influence antitumor effects of regorafenib.

Pleural synovial sarcoma patient treated with combined chemotherapy and Endostar, plus sunitinib maintenance therapy: A case report and review of the literature

Synovial sarcoma is a rare, highly malignant soft-tissue tumor that occurs primarily in the extremities. At present, there is no effective clinical treatment for this condition. The present study reports the case of a 49-year-old male who was diagnosed with pleural synovial sarcoma and treated with recombinant human endostatin (Endostar) combined with chemotherapy for a total of six cycles, followed by sunitinib maintenance therapy. To the best of our knowledge, this is the first reported use of sunitinib for maintenance therapy in pleural synovial sarcoma. The patient survived for 25 months after the recurrence of the disease following surgery. The results indicate that this combination therapy was effective in the treatment of pleural synovial sarcoma. The present study also briefly reviews the literature on pleural synovial sarcoma, and the features and treatments for this rare case are discussed.

KRAS and HRAS mutations confer resistance to MET targeting in preclinical models of MET-expressing tumor cells

The MET receptor tyrosine kinase is often deregulated in human cancers and several MET inhibitors are evaluated in clinical trials. Similarly to EGFR, MET signals through the RAS-RAF-ERK/MAPK pathway which plays key roles in cell proliferation and survival. Mutations of genes encoding for RAS proteins, particularly in KRAS, are commonly found in various tumors and are associated with constitutive activation of the MAPK pathway. It was shown for EGFR, that KRAS mutations render upstream EGFR inhibition ineffective in EGFR-positive colorectal cancers. Currently, there are no clinical studies evaluating MET inhibition impairment due to RAS mutations. To test the impact of RAS mutations on MET targeting, we generated tumor cells responsive to the MET inhibitor EMD1214063 that express KRAS G12V, G12D, G13D and HRAS G12V variants. We demonstrate that these MAPK-activating RAS mutations differentially interfere with MET-mediated biological effects of MET inhibition. We report increased residual ERK1/2 phosphorylation indicating that the downstream pathway remains active in presence of MET inhibition. Consequently, RAS variants counteracted MET inhibition-induced morphological changes as well as anti-proliferative and anchorage-independent growth effects. The effect of RAS mutants was reversed when MET inhibition was combined with MEK inhibitors AZD6244 and UO126. In an in vivo mouse xenograft model, MET-driven tumors harboring mutated RAS displayed resistance to MET inhibition. Taken together, our results demonstrate for the first time in details the role of KRAS and HRAS mutations in resistance to MET inhibition and suggest targeting both MET and MEK as an effective strategy when both oncogenic drivers are expressed.

Role of the ERK1/2 pathway in tumor chemoresistance and tumor therapy

Chemotherapy is one of the important methods for treatment in tumors. However, many tumor patients may experience tumor recurrence because of treatment failure due to chemoresistance. Although many signaling pathways could influence chemoresistance of tumor cells, the extracellular signal-regulated kinase 1 and 2 (ERK1/2) pathway has gained significant attention because of its implications in signaling and which has crosstalk with other signaling pathways. Extensive studies conclude that ERK1/2 pathway is responding to chemoresistance in many kinds of malignant tumors. The aim of this review is to discuss on the role of ERK1/2 pathway in chemoresistance and therapy of tumors. A comprehensive understanding of ERK1/2 pathway in chemoresistance of tumors could provide novel avenues for treatment strategies of tumors.

KRAS status and resistance to epidermal growth factor receptor tyrosine-kinase inhibitor treatment in patients with metastatic colorectal cancer: a meta-analysis

AIM

This study reviewed the association between KRAS mutation and resistance to treatment with epidermal growth factor receptor (EGFR) tyrosine-kinase inhibitors (TKIs) in patients with metastatic colorectal cancer (mCRC).

METHOD

A search was carried out of PubMed, MEDLINE, EMBASE and the Cochrane Library databases (to November 2013) without language restrictions.

RESULTS

Ten studies were included in the final meta-analysis, consisting of 1339 patients with mCRC, of whom 427 (32%) had a KRAS mutation. The objective response rate (ORR) of mCRC patients with KRAS mutation was 8% (33/427), whereas the ORR of mCRC patients with wild-type KRAS was 34% (306/912). The overall pooled response rate (RR) for the ORR was 1.297 (95% CI 1.244-1.353, P < 0.01). Subgroup analysis comparing cetuximab monotherapy treatment with cetuximab plus chemotherapy, showed a pooled RR of 1.26 (95% CI 1.12-0.63, P < 0.01) and 1.30 (95% CI 1.25-1.36, P < 0.01), respectively. For patients receiving anti-EGFR with monoclonal antibodies (mAb) given as first-line treatment or not, the pooled RRs were 1.34 (95% CI 1.23-1.46, P < 0.01) and 1.29 (95% CI 1.23-1.35, P < 0.01). The data on progression-free survival from five studies in the meta-analysis gave a hazard ratio (HR) of 1.99 with a 95% CI of 1.69-2.29. Finally, the data for overall survival in mCRC patients were pooled from the only three studies reporting the HR (1.80; 95% CI 1.50-2.10). None of the results had any evidence of heterogeneity.

CONCLUSION

All the results favoured a stronger link between mutant KRAS and anti-EGFR mAb, but due to a mutually exclusive relationship between KRAS and other gene mutations the clinical usefulness of KRAS mutation as a selection marker for sensitivity to EGFR TKIs in mCRC is limited.