Intraperitoneal injection of adenovirus expressing antisense K-ras RNA suppresses peritoneal dissemination of hamster syngeneic pancreatic cancer without systemic toxicity

Clinicopathological significance of EGFR pathway gene mutations and CRTC1/3-MAML2 fusions in salivary gland mucoepidermoid carcinoma

AIMS

Mucoepidermoid carcinoma (MEC) is one of the most common salivary gland carcinomas. Epidermal growth factor receptor (EGFR) signalling pathway gene mutations are important in predicting a patient's prognosis, selecting molecularly targeted drugs and estimating the efficacy of a molecular therapy. However, their significance in MEC have been poorly clarified. CRTC1/3-MAML2 fusions are specific to MEC and may be associated with favourable characteristics in these patients.

METHODS AND RESULTS

We looked for CRTC1/3-MAML2 fusions and gene alterations in the EGFR, RAS family (KRAS, HRAS and NRAS), PIK3CA, BRAF and AKT1 in 101 MEC cases. We also examined mutations in TP53. CRTC1/3-MAML2 fusions were found in 62.4% of the cases. KRAS, HRAS and PIK3CA mutations were detected in 6.9%, 2.0% and 6.9%, respectively, but other EGFR pathway genes were not mutated. In total, gene mutations (RAS/PIK3CA) in the EGFR pathway were detected in 14.9% of the cases. TP53 mutations were found in 20.8%. CRTC1/3-MAML2 fusions were associated with a better prognosis and RAS/PIK3CA mutations a worse prognosis of the patients, respectively, and both were selected as independent prognostic factors for the overall survival of the patients. TP53 mutations had no prognostic impact. CRTC1/3-MAML2 fusion-positive rates were inversely associated with the patients' age and the fusions were found in 82% of patients aged < 30 years.

CONCLUSIONS

RAS/PIK3CA mutations were frequently detected, and may be a biomarker for a poorer prognosis in MEC patients. CTRC1/3-MAML2 fusions were positive in most of the young MEC patients.

Mutation analysis of the EGFR pathway genes, EGFR, RAS, PIK3CA, BRAF, and AKT1, in salivary gland adenoid cystic carcinoma

Adenoid cystic carcinoma (AdCC), one of the most common salivary gland carcinomas, usually has a fatal outcome. Epidermal growth factor receptor (EGFR) pathway gene mutations are important in predicting a patient's prognosis and estimating the efficacy of molecular therapy targeting the EGFR pathway. In this study of salivary gland AdCC (SAdCC), we looked for gene mutations in EGFR, RAS family (KRAS, HRAS, and NRAS), PIK3CA, BRAF, and AKT1, using a highly sensitive single-base extension multiplex assay, SNaPshot. Out of 70 cases, EGFR pathway missense mutations were found in 13 (18.6%): RAS mutations in 10 (14.3%), EGFR in one (1.4%), and PIK3CA in 5 (7.1%). None of the cases showed an EGFR deletion by direct sequencing. Concurrent gene mutations were found in three cases (4.3%). EGFR pathway mutations were significantly associated with a shorter disease-free (p = 0.011) and overall survival (p = 0.049) and RAS mutations were as well; (p = 0.010) and (p = 0.024), respectively. The gene fusion status as determined by a FISH assay had no significant association with mutations of the genes involved in the EGFR pathway. In conclusion, EGFR pathway mutations, especially RAS mutations, may be frequent in SAdCC, and associated with a poor prognosis for the patient.

Recent Advances and Prospects for Multimodality Therapy in Pancreatic Cancer

The outcomes for treatment of pancreatic cancer have not improved dramatically in many decades. However, the recent promising results with combination chemotherapy regimens for metastatic disease increase optimism for future treatments. With greater control of overt or occult metastatic disease, there will likely be an expanding role for local treatment modalities, especially given that nearly a third of pancreatic cancer patients have locally destructive disease without distant metastatic disease at the time of death. Technical advances have allowed for the safe delivery of dose-escalated radiation therapy, which can then be combined with chemotherapy, targeted agents, immunotherapy, and nanoparticulate drug delivery techniques to produce novel and improved synergistic effects. Here we discuss recent advances and future directions for multimodality therapy in pancreatic cancer.

Prognostic significance of K-ras mutations in pancreatic cancer: a meta-analysis

Background

K-ras gene mutations are common in patients with pancreatic cancer (PC); however, their prognostic value for PC remains inconclusive. This meta-analysis was performed to quantitatively evaluate the association between K-ras mutations and survival in patients with pancreatic cancer.

Methods

We performed a comprehensive search of electronic sources including MEDLINE (via PubMed), Web of Science, and the Cochrane Library. The search covered a publication period from inception to November 2015.

Results

Seventeen studies with a total of 2249 patients with pancreatic cancer were included in the tissue detection of this study. The meta-analysis indicated a significant association between mutant K-ras genes and overall survival (OS) (HR = 1.51, 95 % CI 1.32–1.72, P < 0.001). Moreover, further subgroup analyses by ethnicity, publication year, therapy method, cancer resectability, and gene detection method all revealed that pancreatic cancer patients with the K-ras mutation had significantly poorer OS (P < 0.05). And results from four studies with 225 patients focused on plasma K-ras mutations enhanced such association (HR = 2.23, 95 % CI 1.69–2.95, P < 0.001).

Conclusions

As a prediction of poor prognosis, the detection of K-ras mutations may be a useful prognostic factor for pancreatic cancer patients.

Down-regulating HIF-1α by lentivirus-mediated shRNA for therapy of triple negative breast cancer

Hypoxia is associated with poor response to treatment in various cancers. Hypoxia inducible factor 1 (HIF-1) is a major transcription factor that mediates adaptation of cancer cells to a hypoxic environment and regulates many genes that are involved in key cellular functions, including cell immortalization, stem cell maintenance, autocrine growth/survival, angiogenesis, invasion/metastasis, and resistance to chemotherapy. HIF-1α has been considered as an attractive therapeutic target for cancer treatment, but there is limited success in this research field. In the present study, we designed a recombinant lentivirus containing HIF-1α siRNA, developed stably transfected cell lines, and tested the anticancer effects of the siRNA on cancer cells in vitro and in vivo. Our results indicated that the stable downregulation of HIF-1α reversed chemoresistance, inhibited proliferation, migration and invasion of cancer cells, and slowed down the tumor growth in breast cancer xenograft models. In conclusion, the recombinant lentivirus containing HIF-1α siRNA provides a new avenue for developing novel therapy for triple negative breast cancer.

PIK3CA and PIK3CB silencing by RNAi reverse MDR and inhibit tumorigenic properties in human colorectal carcinoma

Colorectal carcinoma (CRC) is the second most common and frequent cause of cancer-related deaths for men and women in the world. PIK3CA and PIK3CB that reverse multidrug resistance (MDR) can serve as predictive and prognostic markers as well as therapeutic targets for CRC treatment. In the present study, we showed that PIK3CA and PIK3CB are upregulated in CRCs and positively correlated with MDR-1, LRP, and GST-π. Long-term monitoring of 316 CRC patients showed that PIK3CA and PIK3CB were associated with poor survival time as shown by Kaplan-Meier analysis. Furthermore, we found that the downregulation of PIK3CA and PIK3CB reversed MDR; inhibited the capability of proliferation, migration, and invasion of CRC cells; and slowed down the CRC tumor growth in nude mice. Consistent with clinical observations, PIK3CA and PIK3CB significantly increase multidrug resistance of CRC cells in vivo. Together, these results suggest that PIK3CA and PIK3CB may be used as potential therapeutic drug targets for colorectal cancer.

Biodegradable nanoparticle-mediated K-ras down regulation for pancreatic cancer gene therapy

Biodegradable nanoparticle-mediated K-ras siRNA delivery has shown inhibition of cell proliferation, migration and invasion in pancreatic cancer cells.

Gene therapy in pancreatic cancer

Pancreatic cancer (PC) is a highly lethal disease and notoriously difficult to treat. Only a small proportion of PC patients are eligible for surgical resection, whilst conventional chemoradiotherapy only has a modest effect with substantial toxicity. Gene therapy has become a new widely investigated therapeutic approach for PC. This article reviews the basic rationale, gene delivery methods, therapeutic targets and developments of laboratory research and clinical trials in gene therapy of PC by searching the literature published in English using the PubMed database and analyzing clinical trials registered on the Gene Therapy Clinical Trials Worldwide website (http://www. wiley.co.uk/genmed/ clinical). Viral vectors are main gene delivery tools in gene therapy of cancer, and especially, oncolytic virus shows brighter prospect due to its tumor-targeting property. Efficient therapeutic targets for gene therapy include tumor suppressor gene p53, mutant oncogene K-ras, anti-angiogenesis gene VEGFR, suicide gene HSK-TK, cytosine deaminase and cytochrome p450, multiple cytokine genes and so on. Combining different targets or combination strategies with traditional chemoradiotherapy may be a more effective approach to improve the efficacy of cancer gene therapy. Cancer gene therapy is not yet applied in clinical practice, but basic and clinical studies have demonstrated its safety and clinical benefits. Gene therapy will be a new and promising field for the treatment of PC.

Progress in gene therapy for prostate cancer

Gene therapy has held promise to correct various disease processes. Prostate cancer represents the second leading cause of cancer death in American men. A number of clinical trials involving gene therapy for the treatment of prostate cancer have been reported. The ability to efficiently transduce tumors with effective levels of therapeutic genes has been identified as a fundamental barrier to effective cancer gene therapy. The approach utilizing gene therapy in prostate cancer patients at our institution attempts to address this deficiency. The sodium-iodide symporter (NIS) is responsible for the ability of the thyroid gland to transport and concentrate iodide. The characteristics of the NIS gene suggest that it could represent an ideal therapeutic gene for cancer therapy. Published results from Mayo Clinic researchers have indicated several important successes with the use of the NIS gene and prostate gene therapy. Studies have demonstrated that transfer of the human NIS gene into prostate cancer using adenovirus vectors in vitro and in vivo results in efficient uptake of radioactive iodine and significant tumor growth delay with prolongation of survival. Preclinical successes have culminated in the opening of a phase I trial for patients with advanced prostate disease which is currently accruing patients. Further study will reveal the clinical promise of NIS gene therapy in the treatment of prostate as well as other malignancies.

Review article: gene therapy, recent developments and future prospects in gastrointestinal oncology

BACKGROUND

Gene therapy consists of the introduction of genetic material into cells for a therapeutic purpose. A wide range of gene therapy vectors have been developed and used for applications in gastrointestinal oncology.

AIM

To review recent developments and published clinical trials concerning the application of gene therapy in the treatment of liver, colon and pancreatic cancers.

METHODS

Search of the literature published in English using the PubMed database.

RESULTS

A large variety of therapeutic genes are under investigation, such as tumour suppressor, suicide, antiangiogenesis, inflammatory cytokine and micro-RNA genes. Recent progress concerns new vectors, such as oncolytic viruses, and the synergy between viral gene therapy, chemotherapy and radiation therapy. As evidence of these basic developments, recently published phase I and II clinical trials, using both single agents and combination strategies, in adjuvant or advanced disease settings, have shown encouraging results and good safety records.

CONCLUSIONS

Cancer gene therapy is not yet indicated in clinical practice. However, basic and clinical advances have been reported and gene therapy is a promising, new therapeutic approach for the treatment of gastrointestinal tumours.

Pancreatic cancer: gene therapy approaches and gene delivery systems

IMPORTANCE OF THE FIELD

Due to the absence of early diagnosis, the highly invasive and metastatic features and the lack of effective therapeutic modalities, the prognosis of patients with pancreatic cancer is poor. Gene therapy is currently regarded as a potential and promising therapeutic modality for pancreatic cancer.

AREAS COVERED IN THIS REVIEW

This article summarizes an update of gene therapy approaches and reviews the latest progress in gene delivery systems that have been tested on pancreatic cancer.

WHAT THE READER WILL GAIN

The treatment effectiveness of gene combination therapy is better than that of the regulation of single-gene or single gene therapy approaches. Naked DNA is limited because of degradation by intracellular and extracellular nucleases. Virus vectors show high transfection efficiency but are limited due to immunogenicity, inflammatory response and potential carcinogenicity. Non-viral vectors, such as cationic polymers or inorganic nanoparticles, show an important feature that they can be easily modified, and the progress of materials science will provide more and better non-viral vectors, accordingly improving the efficiency and safety of gene therapy, which will make them the most promising vectors for pancreatic cancer.

A probasin promoter, conditionally replicating adenovirus that expresses the sodium iodide symporter (NIS) for radiovirotherapy of prostate cancer

The sodium iodide symporter (NIS) directs the uptake and concentration of iodide in thyroid cells. We have extended the use of NIS-mediated radioiodine therapy to other types of cancer, we transferred and expressed the sodium-iodide symporter (NIS) gene into prostate, colon, and breast cancer cells using adenoviral vectors. To improve vector efficiency we have developed a conditionally replicating adenovirus (CRAd) in which the E1a gene is driven by the prostate specific promoter, Probasin and the cassette RSV promoter-human NIScDNA-bGH polyA replaces the E3 region (CRAd Ad5PB_RSV-NIS). In vitro infection of the prostate cancer cell line LnCaP resulted in virus replication, cytolysis, and release of infective viral particles. Conversely, the prostate cancer cell line PC-3 (androgen receptor negative) and the pancreatic cancer cell line Panc-1 were refractory to the viral cytopathic effect and did not support viral replication. Radioiodine uptake was readily measurable in LnCaP cells infected with Ad5PB_RSV-NIS 24 hours post-infection, confirming NIS expression. In vivo, LnCaP tumor xenografts in nude mice injected intratumorally with Ad5PB_RSV_NIS CRAd expressed NIS actively as evidenced by ⁹⁹Tc uptake and imaging. Administration of therapeutic ¹³¹I after virus injection significantly increased survival probability in mice carrying xenografted LnCaP tumors compared to virotherapy alone. The data indicate that Ad5PB_RSV_NIS replication is stringently restricted to androgen positive prostate cancer cells and results in effective NIS expression and uptake of radioiodine. This construct may allow multimodal therapy, combining cytolytic virotherapy with radioiodine treatment, to be developed as a novel treatment for prostate cancer.

Adenoviral oncolytic suicide gene therapy for a peritoneal dissemination model of gastric cancer in mice

BACKGROUND

Peritoneal dissemination of gastric cancer is often refractory to systemic therapies. Although adenoviral gene therapy has been reported to be a potentially useful therapeutic modality, the adenovirus itself has a dose-limiting toxicity. A novel system was constructed using adenoviral oncolytic suicide gene therapy targeting carcinoembryonic antigen (CEA), and its therapeutic effect and the possibility to reduce the total viral dose while still preserving the antitumor effect were assessed.

METHODS

Three types of adenoviruses were prepared for this novel system: (A) Ad/CEA-Cre, (B) Ad/lox-CD::UPRT for a Cre/loxP system, and (C) Ad/CEA-E1 for conditionally replicating adenovirus. The antitumor effect of the oncolytic suicide gene therapy (A + B + C) was then evaluated in vitro. Mice bearing peritoneal dissemination of human gastric cancer were treated with either this system (A + B + C) or with a tenfold viral dose of suicide gene therapy (A + B). The adverse effects in terms of hepatotoxicity were then evaluated between the two groups.

RESULTS

The current system (A + B + C) demonstrated significantly better cytotoxic effect for CEA-producing cell lines than did suicide gene therapy (A + B) at the same viral dose in vitro. The effect of oncolytic suicide gene therapy was almost equal to that of the tenfold viral dose of suicide gene therapy in vivo. The hepatotoxicity of the two treated groups was also found to be equivalent.

CONCLUSION

It was possible to reduce the total adenoviral dose of oncolytic suicide gene therapy while still preserving the antitumor effect.

Construction of an MUC-1 promoter driven, conditionally replicating adenovirus that expresses the sodium iodide symporter for gene therapy of breast cancer

Introduction

The sodium iodide symporter (NIS) directs the uptake and concentration of iodide in thyroid cells. This in turn allows radioiodine imaging and therapy for thyroid cancer. To extend the use of NIS-mediated radioiodine therapy to other types of cancer, we successfully transferred and expressed the sodium-iodide symporter (NIS) gene in prostate, colon, and breast cancer cells both in vivo and in vitro by using non-replicating adenoviral vectors.

Methods

To improve virotherapy efficiency, we developed a conditionally replicating adenovirus (CRAd) in which the transcriptional cassette RSV promoter-human NIScDNA-bGH polyA was also inserted at the E3 region. The E1a gene is driven by the tumor-specific promoter MUC-1 in the CRAd Ad5AMUCH_RSV-NIS.

Results

In vitro infection of the MUC-1-positive breast cell line T47D resulted in virus replication, cytolysis, and release of infective viral particles. Conversely, the MUC-1-negative breast cancer cell line MDA-MB-231 was refractory to the viral cytopathic effect and did not support viral replication. The data indicate that Ad5AMUCH_RSV-NIS activity is stringently restricted to MUC-1-positive cancer cells. Radioiodine uptake was readily measurable in T47 cells infected with Ad5AMUCH_RSV-NIS 24 hours after infection, thus confirming NIS expression before viral-induced cell death.

Conclusions

This construct may allow multimodal therapy, combining virotherapy with radioiodine therapy to be developed as a novel treatment for breast and other MUC1-overexpressing cancers.

New pancreatic carcinoma model for studying oncolytic adenoviruses in the permissive Syrian hamster

Syrian hamster is a practical animal model for studying the systemic effects of oncolytic vectors derived from adenovirus serotype 5 (Ad5). Ad5 replicates well in Syrian hamster tissues, and Syrian hamster cell lines are available that are known to support Ad5 replication. In this study, we established four new Syrian hamster cell lines from transplantable pancreatic, renal, hepatic and lung tumors. The pancreatic cell line (SHPC6) and the renal cell line were highly permissive for Ad5 replication. The SHPC6 cell line formed disseminated intraperitoneal tumors when cells were injected into the peritoneal cavity. INGN 007, an oncolytic Ad5-based vector, completely reversed the growth of disseminated intraperitoneal SHPC6 tumor nodules following intraperitoneal injection of the vector, leading to 100% survival of the treated animals. SHPC6 cells also formed subcutaneous tumors, whose growth was suppressed by INGN 007 following intratumoral injection. INGN 007 replicated in both the intraperitoneal and subcutaneous SHPC6 tumors. Following intraperitoneal injection, INGN 007 did not replicate in the livers of hamsters with intraperitoneal SHPC6 tumors, and was not hepatotoxic. These studies suggest that the SHPC6 cell line may be useful as a model for disseminated pancreatic cancer, and that INGN 007 may be a safe and effective vector to treat these tumors.

Anti-tumor activity of ESX1 on cancer cells harboring oncogenic K-ras mutation

Human ESX1 is a 65-kilodalton (kDa) paired-like homeoprotein that is proteolytically processed into N-terminal 45-kDa and C-terminal 20-kDa fragments. The N-terminal ESX1 fragment, which contains the homeodomain, localizes to the nucleus and represses mRNA transcription from the K-ras gene. When we inoculated human colorectal carcinoma HCT116 constitutive expressing N-terminal region of ESX1 (N-ESX1) into nude mice, transfectant cells uniformly showed decreased tumor-forming activity compared with that of the parental cells. Furthermore, pretreatment of HCT116 carcinoma cells with a fusion protein consisting of N-ESX1 and the protein-transduction domain derived from the human immunodeficiency virus type-1 TAT protein gave rise to a dramatic reduction in the tumorigenicity of HCT116 cells in nude mice. Our results provide first in vivo evidence for the molecular targeting therapeutic application of the K-ras repressor ESX1, especially TAT-mediated transduction of N-ESX1, in the treatment of human cancers having oncogenic K-ras mutations.

Preventing liver metastasis by resecting the primary pancreatic carcinoma at an early stage of intrapancreatic transplantation in hamsters

PURPOSE

To determine whether early primary pancreatic tumor resection can prevent liver metastases of intrapancreatic transplantation in a hamster model.

METHODS

Cells from the PGHAM-1 cell line were transplanted into the pancreases of 30 Syrian golden hamsters. A suspension of 5 x 10(6) cells was injected into the splenic lobe of each pancreas. The primary pancreatic tumor was resected in 15 of the hamsters 10 days after transplantation (resection group). Fifteen other animals with transplantation but without resection served as controls (control group). All hamsters were killed 21 days after transplantation. The primary pancreatic tumors were measured for size and volume and examined histologically and immunohistologically for angiogenesis and tumor proliferation.

RESULTS

In the resection group, small pancreatic tumors 4.7 +/- 0.94 mm in diameter were found and resected 10 days after transplantation. Neither pancreatic tumors nor liver metastases were found in the resection group at the end of the experiment. All animals in the control group had pancreatic tumors 12.3 +/- 3.29 mm in size, and 11 of 15 (73.3%) had liver metastases. The primary pancreatic tumors in the group with liver metastasis were significantly larger in diameter and volume than those in this group without liver metastasis (p<0.01). In the control group, proliferation of the primary pancreatic tumor, evaluated according to argyrophilic nucleolar organizer region, showed no differences within the pancreatic tumor group. On the other hand, the microvessel density of pancreatic tumors with liver metastases was significantly higher than that of tumors without liver metastases.

CONCLUSIONS

Our results suggest that 10 days after transplantation, the pancreatic tumors were small in size and volume and ready to proliferate but not yet ready to begin metastasizing through angiogenesis. This is one reason why early resection of the primary tumor prevents liver metastasis.

Expression of nerve growth factor messenger RNA in pancreatic cancer tissues in Sprague Dawley rats

AIM: To establish a model of pancreatic cancer in Sprague-Dawley(SD)rats and to explore the expression and its significance of nerve growth factor(NGF)mRNA in pancreatic cancer and non-cancer tissues.

METHODS: Ninety rats were randomly divided into A (n = 40), B (n = 40) and C (n = 10) group. For group A and B, dimethylbenzanthrancene (DMBA) was directly implanted into the parenchyma of the rat pancreas to establish pancreatic cancer model. The rats in group B were treated with trichostatin(TSA). The rats in group C served as the controls. The rats were executed within 3-5 mo, and the carcinogenesis of the rats was observed by pathological methods. In situ hybridization was used to detect the expression of NGF mRNA in the formalin-fixed and routinely paraffin-embedded sections of pancreatic cancer and non-cancer tissues.

RESULTS: The prevalence rate of pancreatic cancer in group A was 48.7%(18/37) within 3-5 mo, 28.6%(2/7) at mo, 40.0%(4/10) at 4 mo and 60%(12/20) at 5 mo (P > 0.05), and that in group B was 33.3%(12/36), 16.7%(1/6), 30.0%(3/10) and (40.0%)8/20, respectively (P > 0.05). The prevalence rate in group A was higher than that of group B (P > 0.05). The diameters of tumor mass in group A were significantly larger than those in group B (group A: 0.5-1.0 cm 7 cases, 1.0-2.0 cm 10 cases, > 2 cm 1 case vs group B: 0.5-1.0 cm 9 case, 1.0-2.0 cm 2 cases, >2.0 cm 1 case, P < 0.05). No tumor formed in the pancreas of the rats in group C or in other main organs of the rats in group A and B. The positive rate of NGF mRNA expression in the pancreatic ductal cancer tissues was significantly higher than that in non-cancer tissues (67.9% vs 18.6%, P < 0.01), and severely atypical hyperplasia was observed in the positive non-cancer pancreatic tissues of ductal epithelium. The positive rate of NGF mRNA expression in ductal adenocarcinoma was markedly higher in group A than that in group B (P = 0.052). The positive rate of NGF mRNA in the rats with tumor maximal diameter ≤ 1.0 cm was lower than that in the ones with tumor maximal diameter > 1.0 cm (P > 0.05).

CONCLUSION: Direct implantation of DMBA in the parenchyma of pancreas can induce pancreatic cancer with a high occurrence rate in a short time. NGF may play an important role in the carcinogenesis of pancreatic cancer. TSA can inhibit the occurrence and progression of pancreatic cancer by inhibiting NGF expression.

K-ras as a target for cancer therapy

The central role K-, H- and N-Ras play in regulating diverse cellular pathways important for cell growth, differentiation and survival is well established. Dysregulation of Ras proteins by activating mutations, overexpression or upstream activation is common in human tumors. Of the Ras proteins, K-ras is the most frequently mutated and is therefore an attractive target for cancer therapy. The complexity of K-ras signaling presents many opportunities for therapeutic targeting. A number of different approaches aimed at abrogating K-ras activity have been explored in clinical trials. Several of the therapeutic agents tested have demonstrated clinical activity, supporting ongoing development of K-ras targeted therapies. However, many of the agents currently being evaluated have multiple targets and their antitumor effects may not be due to K-Ras inhibition. To date, no selective, specific inhibitor of K-ras is available for routine clinical use. In this review, we will summarize the structure and function of K-ras with attention to its role in tumorigenesis and discuss the successes and failures of the various strategies designed to therapeutically target this important oncogene.