Current landscape of preoperative neoadjuvant therapies for initial resectable colorectal cancer liver metastasis

Colorectal cancer liver metastasis(CRLM)presents a clinical challenge,and optimizing treatment strategies is crucial for improving patient outcomes.Surgical resection,a key element in achieving prolonged survival,is often linked to a heightened risk of recurrence.Acknowledging the potential benefits of preoperative neoadjuvant chemotherapy in managing resectable liver metastases,this approach has gained attention for its role in tumor downsizing,assessing biological behavior,and reducing the risk of postoperative recurrence.However,the use of neoadjuvant chemotherapy in initially resectable CRLM sparks ongoing debates.The balance between tumor reduction and the risk of hepatic injury,coupled with concerns about delaying surgery,necessitates a nuanced approach.This article explores recent research insights and draws upon the practical experiences at our center to address critical issues regarding considerations for initially resectable cases.Examining the criteria for patient selection and the judicious choice of neoadjuvant regimens are pivotal areas of discussion.Striking the right balance between maximizing treatment efficacy and minimizing adverse effects is imperative.The dynamic landscape of precision medicine is also reflected in the evolving role of gene testing,such as RAS/BRAF and PIK3CA,in tailoring neoadjuvant regimens.Furthermore,the review emphasizes the need for a multidisciplinary approach to navigate the comp-lexities of CRLM.Integrating technical expertise and biological insights is crucial in refining neoadjuvant strategies.The management of progression following neoadjuvant chemotherapy requires a tailored approach,acknowledging the diverse biological behaviors that may emerge.In conclusion,this review aims to provide a comprehensive perspective on the considerations,challenges,and advancements in the use of neoadjuvant chemotherapy for initially resectable CRLM.By combining evidencebased insights with practical experiences,we aspire to contribute to the ongoing discourse on refining treatment paradigms for improved outcomes in patients with CRLM.

Molecular mechanisms targeting drug-resistance and metastasis in colorectal cancer:Updates and beyond

Colorectal cancer(CRC)is the third most diagnosed malignancy and a major leading cause of cancer-related deaths worldwide.Despite advances in therapeutic regimens,the number of patients presenting with metastatic CRC(mCRC)is increasing due to resistance to therapy,conferred by a small population of cancer cells,known as cancer stem cells.Targeted therapies have been highly successful in prolonging the overall survival of patients with mCRC.Agents are being developed to target key molecules involved in drug-resistance and metastasis of CRC,and these include vascular endothelial growth factor,epidermal growth factor receptor,human epidermal growth factor receptor-2,mitogen-activated extracellular signal-regulated kinase,in addition to immune checkpoints.Currently,there are several ongoing clinical trials of newly developed targeted agents,which have shown considerable clinical efficacy and have improved the prognosis of patients who do not benefit from conventional chemotherapy.In this review,we highlight recent developments in the use of existing and novel targeted agents against drug-resistant CRC and mCRC.Furthermore,we discuss limitations and challenges associated with targeted therapy and strategies to combat intrinsic and acquired resistance to these therapies,in addition to the importance of implementing better preclinical models and the application of personalized therapy based on predictive biomarkers for treatment selection.

Combining chemotherapy and targeted therapies in metastatic colorectal cancer

Colorectal cancer remains one of the major causes of cancer death worldwide. During the past years, the development of new effective treatment options has led to a considerable improvement in the outcome of this disease. The advent of agents such as capecitabine, irinotecan, oxaliplatin, cetuximab and bevacizumab has translated into median survival times in the range of 2 years. Intense efforts have focused on identifying novel agents targeting specific growth factor receptors, critical signal transduction pathways or mediators of angiogenesis. In addition, several clinical trials have suggested that some of these molecularly targeted drugs can be safely and effectively used in combination with conventional chemotherapy. In this article we review various treatment options combining cytotoxic and targeted therapies currently available for patients with metastatic colorectal cancer.

What enlightenment has the development of lung cancer bone metastasis brought in the last 22 years

BACKGROUND Lung cancer bone metastasis(LCBM)is a disease with a poor prognosis,high risk and large patient population.Although considerable scientific output has accumulated on LCBM,problems have emerged,such as confusing research structures.AIM To organize the research frontiers and body of knowledge of the studies on LCBM from the last 22 years according to their basic research and translation,clinical treatment,and clinical diagnosis to provide a reference for the development of new LCBM clinical and basic research.METHODS We used tools,including R,VOSviewer and CiteSpace software,to measure and visualize the keywords and other metrics of 1903 articles from the Web of Science Core Collection.We also performed enrichment and proteinprotein interaction analyses of gene expression datasets from LCBM cases worldwide.RESULTS Research on LCBM has received extensive attention from scholars worldwide over the last 20 years.Targeted therapies and immunotherapies have evolved into the mainstream basic and clinical research directions.The basic aspects of drug resistance mechanisms and parathyroid hormone-related protein may provide new ideas for mechanistic study and improvements in LCBM prognosis.The produced molecular map showed that ribosomes and focal adhesion are possible pathways that promote LCBM occurrence.CONCLUSION Novel therapies for LCBM face animal testing and drug resistance issues.Future focus should centre on advancing clinical therapies and researching drug resistance mechanisms and ribosome-related pathways.

Role of targeted therapy in metastatic colorectal cancer

Colorectal cancer(CRC) is a significant cause of cancer-related morbidity and mortality all over the world.Improvements of cytotoxic and biologic agents have prolonged the survival in metastatic CRC(mC RC),with a median overall survival of approximately 2 years and more in the past two decades.The biologic agents that have proven clinical benefits in m CRC mainly target vascular endothelial growth factor(VEGF) and epidermal growth factor receptor(EGFR).In particular,bevacizumab targeting VEGF and cetuximab and panitumumab targeting EGFR have demonstrated sig-nificant survival benefits in combination with cytotoxic chemotherapy in the first-line,second-line,or salvage setting.Aflibercept,ramucirumab,and regorafenib are also used in second-line or salvage therapy.Recent retrospective analyses have shown that KRAS or NRAS mutations were negative predictive markers for anti-EGFR therapy.Based on the evidence from large rand-omized clinical trials,personalized therapy is necessary for patients with m CRC according to their tumor biology and characteristics.The aim of this paper was to summarize the results of the major randomized clinical trials and highlight the benefits of the molecular targeted agents in patients with mC RC.

Radiofrequency ablation as treatment for pulmonary metastasis of colorectal cancer

Radiofrequency ablation (RFA) causes focal coagulation necrosis in tissue. Its first clinical application was reported in 2000, and RFA has since been commonly used in both primary and metastatic lung cancer. The procedure is typically performed using computed tomography guidance, and the techniques for introducing the electrode to the tumor are simple and resemble those used in percutaneous lung biopsy. The most common complication is pneumothorax, which occurs in up to 50% of procedures; chest tube placement for pneumothorax is required in up to 25% of procedures. Other severe complications, such as pleural effusion requiring chest tube placement, infection, and nerve injury, are rare. The local efficacy depends on tumor size, and local progression after RFA is not rare, occurring in 10% or more of patients. The local progression rate is particularly high for tumors > 3 cm. Repeat RFA may be used to treat local progression. Short- to mid-term survival after RFA appears promising and is approximately 85%-95% at 1 year and 45%-55% at 3 years. Long-term survival data are sparse. Better survival may be expected for patients with small metastasis, low carcinoembryonic antigen levels, and/or no extrapulmonary metastasis. The notable advantages of RFA are that it is simple and minimally invasive; preserves pulmonary function; can be repeated; and is applicable regardless of previous treatments. Its most substantial limitation is limited local efficacy. Although surgery is still the method of choice for treatment with curative intent, the ultimate application of RFA may be to replace metastasectomy for small metastases. Randomized trials comparing RFA with surgery are needed.

Advances in therapeutics for liver metastasis from colorectal cancer

The evolution of chemotherapeutic regimens that include targeted molecular agents has resulted in a breakthrough in the management of advanced colorectal liver metastasis (CLM), improving the progression-free survival after liver resection, and rendering initially unresectable liver tumors resectable, with reported resection rates ranging from 13% to 51%. In addition, the criteria used for selecting patients for hepatectomy have been expanding because of advances in surgical techniques and improvements in chemotherapy. However, the increasing use of chemotherapy has raised concern about potential hepatotoxicities such as steatosis, chemotherapy-associated steatohepatitis, and sinusoidal obstruction syndrome, and their deleterious effects on postoperative outcome. The present review focuses on the advantages and disadvantages of chemotherapy, strategies for the prevention and diagnosis of chemotherapy-associated liver injury, and the adoption of more aggressive surgical approaches, which have changed the traditional paradigm for CLM.

Wingless/It/β-catenin signaling in liver metastasis from colorectal cancer:A focus on biological mechanisms and therapeutic opportunities

The liver is the most common site of metastases in patients with colorectal cancer.Colorectal liver metastases(CRLMs)are the result of molecular mechanisms that involve different cells of the liver microenvironment.The aberrant activation of Wingless/It(Wnt)/β-catenin signals downstream of Wnt ligands initially drives the oncogenic transformation of the colon epithelium,but also the progression of metastatization through the epithelial-mesenchymal transition/mesenchymalepithelial transition interactions.In liver microenvironment,metastatic cells can also survive and adapt through dormancy,which makes them less susceptible to pro-apoptotic signals and therapies.Treatment of CRLMs is challenging due to its variability and heterogeneity.Advances in surgery and oncology have been made in the last decade and a pivotal role for Wnt/β-catenin pathway has been recognized in chemoresistance.At the state of art,there is a lack of clear understanding of why and how this occurs and thus where exactly the opportunities for developing anti-CRLMs therapies may lie.In this review,current knowledge on the involvement of Wnt signaling in the development of CRLMs was considered.In addition,an overview of useful biomarkers with a revision of surgical and non-surgical therapies currently accepted in the clinical practice for colorectal liver metastasis patients were provided.

Remarkably Reduced Expression of FoxO3a in Metaplastic Colorectum, Primary Colorectal Cancer and Liver Metastasis

The forkhead family members of transcription factors （FoxOs） are expected to be potential cancer-related drug targets and thus are being extremely studied recently. In the present study, FoxO3a, one major member of this family, was identified to be down-regulated in colorectal cancer through mi- cro-array analysis, which was confirmed by RT-PCR and Western blot in 28 patients. Moreover, immu- nohistochemistry （IHC） showed that the expression levels of FoxO3a were remarkably reduced in 99 cases of primary colorectal cancer, liver metastasis, and even in metaplastic colorectal tissue. IHC also revealed an exclusion of FoxO3a from the nucleus of most cells of tumor-associated tissues. Silencing FoxO3a by siRNA led to elevation of G2-M phase cells. We conclude that the downregulation of FoxO3a may greatly contribute to tumor development, and thus FoxO3a may represent a novel thera- peutic target in colorectal cancer.

Therapy for non-small-cell lung cancer patients with brain metastasis

Brain metastasis is a major cause of poor prognosis and high mortality for non-small cell lung cancer patients. The prognosis of non-small-cell lung cancer(NSCLC) patients with brain metastasis is generally poor and more effective treatment is required to improve their prognosis. Whole-brain radiotherapy, surgery, stereotactic radiosurgery, chemotherapy and targeted therapy are the main treatment for brain metastasis. This review focuses on the five therapeutic strategy and in particular, on targeted therapy.

Association between liver targeted antiviral therapy in colorectal cancer and survival benefits:An appraisal

In colorectal cancer(CRC),liver metastasis remains a major contributor to the cause of cancer-related death.Putative biomarkers,therapeutic efficacy,and drug insensitivity still pose clinical challenges for metastatic CRC patients.Interestingly,previous studies indicated that tumor cells in CRC did not metastasize to the injured liver,which included hepatitis or cirrhotic liver.The benefits of antiviral therapy on hepatocellular carcinoma have also been identified.This review discusses the role of antiviral therapy on the liver.Antiviral therapy may reduce potential liver metastasis associated with CRC in several mechanistic aspects.

Development of a new choroidal metastasis in resistance to crizotinib therapy in anaplastic lymphoma kinaserearranged non-small cell lung cancer

INTRODUCTION Non-small cell lung cancer（NSCLC）is a common malignant disease with an extremely poor prognosis.Lung cancer has been reported to metastasize to the eye in 0.2%to7%of patients based on clinical studies,and in 6%to 7%of patients based on postmortem histopathologic studies.

Neoadjuvant chemotherapy for metastatic colorectal cancer to the liver: from chemotherapy to targeting therapy

Despite the advances in surgical techniques, adjuvant chemotherapy and targeted therapy, approximately 40%-70% of patients with progressive colorectal cancer will develop liver metastases, of whom one-third are found at the time of diagnosis.[1] Surgical resection is now the standard treatment and also the only potentially curative treatment for resectable lesions.

Colorectal cancer:Recent advances in management and treatment

Colorectal cancer(CRC)is the third most common cancer worldwide,and the second most common cause of cancer-related death.In 2020,the estimated number of deaths due to CRC was approximately 930000,accounting for 10%of all cancer deaths worldwide.Accordingly,there is a vast amount of ongoing research aiming to find new and improved treatment modalities for CRC that can potentially increase survival and decrease overall morbidity and mortality.Current management strategies for CRC include surgical procedures for resectable cases,and radiotherapy,chemotherapy,and immunotherapy,in addition to their combination,for non-resectable tumors.Despite these options,CRC remains incurable in 50%of cases.Nonetheless,significant improvements in research techniques have allowed for treatment approaches for CRC to be frequently updated,leading to the availability of new drugs and therapeutic strategies.This review summarizes the most recent therapeutic approaches for CRC,with special emphasis on new strategies that are currently being studied and have great potential to improve the prognosis and lifespan of patients with CRC.

Chemotherapy combined with bevacizumab for small cell lung cancer with brain metastases:A case report

BACKGROUND Small cell lung cancer(SCLC)is a common and aggressive subtype of lung cancer.It is characterized by rapid growth and a high mortality rate.Approximately 10%of patients with SCLC present with brain metastases at the time of diagnosis,which is associated with a median survival of 5 mo.This study aimed to summarize the effect of bevacizumab on the progression-free survival(PFS)and overall survival of patients with brain metastasis of SCLC.CASE SUMMARY A 62-year-old man was referred to our hospital in February 2023 because of dizziness and numbness of the right lower extremity without headache or fever for more than four weeks.The patient was diagnosed with limited-stage SCLC.He received 8 cycles of chemotherapy combined with maintenance bevacizumab therapy and achieved a PFS of over 7 mo.CONCLUSION The combination of bevacizumab and irinotecan effectively alleviated brain metastasis in SCLC and prolonged PFS.

Expression and significance of pigment epithelium-derived factor and vascular endothelial growth factor in colorectal adenoma and cancer

BACKGROUND The incidence and mortality of colorectal cancer(CRC)are among the highest in the world,and its occurrence and development are closely related to tumor neovascularization.When the balance between pigment epithelium-derived factors(PEDF)that inhibit angiogenesis and vascular endothelial growth factors(VEGF)that stimulate angiogenesis is broken,angiogenesis is out of control,resulting in tumor development.Therefore,it is very necessary to find more therapeutic targets for CRC for early intervention and later treatment.AIM To investigate the expression and significance of PEDF,VEGF,and CD31-stained microvessel density values(CD31-MVD)in normal colorectal mucosa,adenoma,and CRC.METHODS In this case-control study,we collected archived wax blocks of specimens from the Digestive Endoscopy Center and the General Surgery Department of Chengdu Second People's Hospital from April 2022 to October 2022.Fifty cases of specimen wax blocks were selected as normal intestinal mucosa confirmed by electronic colonoscopy and concurrent biopsy(normal control group),50 cases of specimen wax blocks were selected as colorectal adenoma confirmed by electronic colonoscopy and pathological biopsy(adenoma group),and 50 cases of specimen wax blocks were selected as CRC confirmed by postoperative pathological biopsy after inpatient operation of general surgery(CRC group).An immunohistochemical staining experiment was carried out to detect PEDF and VEGF expression in three groups of specimens,analyze their differences,study the relationship between the two and clinicopathological factors in CRC group,record CD31-MVD in the three groups,and analyze the correlation of PEDF,VEGF,and CD31-MVD in the colorectal adenoma group and the CRC group.The F test or adjusted F test is used to analyze measurement data statistically.Kruskal-Wallis rank sum test was used between groups for ranked data.The chi-square test,adjusted chi-square test,or Fisher's exact test were used to compare the rates between groups.All differences between groups were compared using the Bonferroni method for multiple comparisons.Spearman correlation analysis was used to test the correlation of the data.The test level(α)was 0.05,and a two-sided P<0.05 was considered statistically significant.RESULTS The positive expression rate and expression intensity of PEDF were gradually decreased in the normal control group,adenoma group,and CRC group(100%vs 78%vs 50%,χ^(2)=34.430,P<0.001;++~++vs+~++vs-~+,H=94.059,P<0.001),while VEGF increased gradually(0%vs 68%vs 96%,χ^(2)=98.35,P<0.001;-vs-~+vs++~+++,H=107.734,P<0.001).In the CRC group,the positive expression rate of PEDF decreased with the increase of differen-tiation degree,invasion depth,lymph node metastasis,distant metastasis,and TNM stage(χ^(2)=20.513,4.160,5.128,6.349,5.128,P<0.05);the high expression rate of VEGF was the opposite(χ^(2)=10.317,13.134,17.643,21.844,17.643,P<0.05).In the colorectal adenoma group,the expression intensity of PEDF correlated negatively with CD31-MVD(r=-0.601,P<0.001),whereas VEGF was not significantly different(r=0.258,P=0.07).In the CRC group,the expression intensity of PEDF correlated negatively with the expression intensity of CD31-MVD and VEGF(r=-0.297,P<0.05;r=-0.548,P<0.05),while VEGF expression intensity was positively related to CD31-MVD(r=0.421,P=0.002).CONCLUSION It is possible that PEDF can be used as a new treatment and prevention target for CRC by upregulating the expression of PEDF while inhibiting the expression of VEGF.

MicroRNAs in the prognosis and therapy of colorectal cancer: From bench to bedside

MicroRNAs(miRNAs) are small, single-stranded, noncoding RNAs that can post-transcriptionally regulate the expression of various oncogenes and tumor suppressor genes. Dysregulated expression of many miRNAs have been shown to mediate the signaling pathways critical in the multistep carcinogenesis of colorectal cancer(CRC). MiR NAs are stable and protected from RNase-mediated degradation, thereby enabling its detection in biological fluids and archival tissues for biomarker studies. This review focuses on the role and application of miRNAs in the prognosis and therapy of CRC. While stage Ⅱ CRC is potentially curable by surgical resection, a significant percentage of stage Ⅱ CRC patients do develop recurrence. MiRNA biomarkers may be used to stratify such high-risk population for adjuvant chemotherapy to provide better prognoses. Growing evidence also suggests that miRNAs are involved in the metastatic process of CRC. Certain of these miRNAs may thus be used as prognostic biomarkers to identify patients more likely to have micro-metastasis, who could be monitored more closely after surgery and/or given more aggressive adjuvant chemotherapy. Intrinsic and acquired resistance to chemotherapy severely hinders successful chemotherapy in CRC treatment. Predictive miRNA biomarkers for response to chemotherapy may identify patients who will benefit the most from a particular regimen and also spare the patients from unnecessary side effects. Selection of patients to receive the new targeted therapy is becoming possible with the use of predictive miRNA biomarkers. Lastly, forced expression of tumor suppressor miRNA or silencing of oncogenic miRNA in tumors by gene therapy can also be adopted to treat CRC alone or in combination with other chemotherapeutic drugs.

Novel targeting approaches and signaling pathways of colorectal cancer: An insight

Colorectal cancer(CRC) is the third most common cancer of mortality in the world. Chemotherapy based treatment leads to innumerable side effects as it delivers the anticancer drug to both normal cells besides cancer cells. Sonic Hedgehog(SHH), Wnt wingless-type mouse mammary tumor virus/β-catenin, transforming growth factor-β/SMAD, epidermal growth factor receptor and Notch are the main signaling pathways involved in the progression of CRC. Targeted therapies necessitate information regarding the particular aberrant pathways. Advancements in gene therapies have resulted in the recognition of novel therapeutic targets related with these signal-transduction cascades. CRC is a stepwise process where mutations occur over the time and activation of oncogenes and deactivation of tissue suppressor genes takes place. Genetic changes which are responsible for the induction of carcinogenesis include loss of heterozygosity in tumor suppressor genes such as adenomatous polyposis coli, mutation or deletion of genes like p53 and K-ras. Therefore, many gene-therapy approaches like gene correction, virusdirected enzyme-prodrug therapy, immunogenetic manipulation and virotherapy are currently being explored. Development of novel strategies for the safe and effective delivery of drugs to the cancerous site is the need of the hour. This editorial accentuates different novel strategies with emphasis on gene therapy and immunotherapy for the management of CRC.

Review of the current targeted therapies for non-small-cell lung cancer

The last decade has witnessed the development of oncogene-directed targeted therapies that have significantly changed the treatment of non-small-cell lung cancer(NSCLC). In this paper we review the data demonstrating efficacy of gefitinib, erlotinib, and afatinib, which target the epidermal growth factor receptor(EGFR), and crizotinib which targets anaplastic lymphoma kinase(ALK). We discuss the challenge of acquired resistance to these small-molecular tyrosine kinase inhibitors and review promising agents which may overcome resistance, including the EGFR T790 Mtargeted agents CO-1686 and AZD9291, and the ALKtargeted agents ceritinib(LDK378), AP26113, alectinib(CH/RO5424802), and others. Emerging therapies directed against other driver oncogenes in NSCLC including ROS1, HER2, and BRAF are covered as well. The identification of specific molecular targets in a significant fraction of NSCLC has led to the personalized deployment of many effective targeted therapies, with more to come.

Anti-EGFR and anti-VEGF agents:Important targeted therapies of colorectal liver metastases

Colorectal liver metastasis (CLM) is common worldwide. Targeted therapies with monoclonal antibodies have been proven effective in numerous clinical trials, and are now becoming standards for patients with CLM. The development and application of anti-epidermal growth factor receptor (anti-EGFR) and anti-vascular endothelial growth factor (anti-VEGF) antibodies represents significant advances in the treatment of this disease. However, new findings continue to emerge casting doubt on the efficacy of this approach. The Kirsten rat sarcoma viral oncogene (KRAS) has been proven to be a crucial predictor of the success of anti-EGFR treatment in CLM. Whereas a recent study summarized several randomized controlled trials, and showed that patients with the KRAS G13D mutation significantly benefited from the addition of cetuximab in terms of progress-free survival (PFS, 4.0 mo vs 1.9 mo, HR = 0.51, P = 0.004) and overall survival (OS, 7.6 mo vs 5.7 mo, HR = 0.50, P = 0.005). Some other studies also reported that the KRAS G13D mutation might not be absolutely predictive of non-responsiveness to anti-EGFR therapy. At the same time, &#x0201c;new&#x0201d; RAS mutations, including mutations in neuroblastoma RAS viral (v-ras) oncogene homolog (NRAS) and exons 3 and 4 of KRAS, have been suggested to be predictors of a poor treatment response. This finding was first reported by the update of the PRIME trial. The update showed that for patients with non-mutated KRAS exon 2 but other RAS mutations, panitumumab-fluorouracil, leucovorin, and oxaliplatin (FOLFOX)4 treatment led to inferior PFS (HR = 1.28, 95%CI: 0.79-2.07) and OS (HR = 1.29, 95%CI: 0.79-2.10), which was consistent with the findings in patients with KRAS mutations in exon 2. Then, the update of the PEAK trial and the FIRE-III trial also supported this finding, which would reduce candidates for anti-EGFR therapy but enhance the efficacy. In first-line targeted combination therapy, the regimens of cetuximab plus FOLFOX was called into question because of the inferior prognosis in the COIN trial and the NORDIC-VII trial. Also, bevacizumab plus oxaliplatin-based chemotherapy was questioned because of the NO16966 trial. By the update and further analysis of the COIN trial and the NORDIC-VII trial, cetuximab plus FOLFOX was reported to be reliable again. But bevacizumab plus oxaliplatin-based chemotherapy was still controversial. In addition, some trials have reported that bevacizumab is not suitable for conversion therapy. The results of the FIRE-III trial showed that cetuximab led to a significant advantage over bevacizumab in response rate (72% vs 63%, P = 0.017) for evaluable population. With the balanced allocation of second-line treatment, the FIRE-III trial was expected to provide evidence for selecting following regimens after first-line progression. There is still no strong evidence for the efficacy of targeted therapy as a preoperative treatment for resectable CLM or postoperative treatment for resected CLM, although the combined regimen is often administered based on experience. Combination therapy with more than one targeted agent has been proven to provide no benefit, and even was reported to be harmful as first-line treatment by four large clinical trials. However, recent studies reported positive results of erlotinib plus bevacizumab for maintenance treatment. The mechanism of antagonism between different targeted agents deserves further study, and may also provide greater understanding of the development of resistance to targeted agents.