结直肠癌分子分型临床研究进展

结直肠癌是生物学高度异质性的肿瘤,染色体不稳定性(chromosomal instahility,CIN)、微卫星不稳定(microsatel liteinstability,MSI)、通过CpG岛甲基化的表基因沉默(epigenetic sileneing through the CpG Island Methylator phenotype,CIMP)是目前临床预测、预后和指导治疗的重要分子机制。随着分子生物学技术的不断进步,可以根据CIN,MSI,CIMP在遗传学和表遗传学中的表达状态将CRC分6个亚群,即MSI-H,CIMP-H;MSI-H,CIMP-Low/0;MSI-L/MSS,CIMP-H;MSI-L,CIMP-Low;MSS,CIMP-Low;MSI-L/MSS,CIMP-0,它们在临床、病理、分子特征、治疗反应和生存期都有所不同。因此,对结直肠癌进行分子分型有利于判断患者的临床预后和指导临床治疗。文章就以上问题进行了综述。     

微卫星不稳定性在结直肠癌中的意义

 微卫星不稳定性（MSI）是结直肠癌发生发展的重要分子机制,对结直肠癌具有重要临床意义。MSI是林奇综合征的诊断标志物。同时由于MSI阳性的结直肠癌比阴性者表现出更好的预后,且对5-氟尿嘧啶类化疗药物不敏感,MSI同样成为结直肠癌的预后和预测化疗疗效的标志物。     

微卫星不稳定性判断结直肠癌预后和预测化疗疗效相关研究进展

结直肠癌是一种常见恶性肿瘤, 近年来, 微卫星不稳定性与结直肠癌的关系成为判断结直肠癌预后和预测化疗疗效方面研究的一个热点。微卫星不稳定性在判断结直肠癌的预后及指导结直肠癌的化疗方面有着重要作用。本文从微卫星不稳定性的概念, 与结直肠癌预后相关性, 与各期结直肠癌氟尿嘧啶类药物疗效间相关性等方面对微卫星不稳定性在结直肠癌中的相关进展进行综述, 旨在为临床上应用微卫星不稳定性指导结直肠癌治疗方面提供相关依据。 < /span >      

微卫星不稳定性检测在结直肠外科的应用及其临床意义

结直肠癌中约15%患者存在基因组微卫星高度不稳定(MSI-H),最新的美国国立综合癌症网络与中国临床肿瘤学会指南均推荐所有结直肠癌患者都要进行微卫星不稳定(MSI)检测以判断预后,并可以用于林奇综合征的诊断与筛查;早发性结直肠癌患者的MSI-H频率更高,且好发于近端结肠(右半结肠),所以临床上对于年轻的结直肠癌患者,尤其是右半结肠癌患者,更应该重视MSI的检测。MSI-H的结直肠癌患者预后更好,免疫治疗对于MSI-H的结直肠癌疗效显著,目前国内外指南均建议MSI-H的结直肠癌全线推荐免疫治疗,但是MSI-H的误诊可能导致免疫一线治疗患者疾病进展,所以结直肠外科医师需要积极探索新的错配修复基因通路蛋白、微卫星不稳定性的检测位点及新的检测方式,以提高诊断准确率。     

结直肠癌靶向药物耐药机制研究进展

结直肠癌临床高发,并且近年来结直肠癌的发病率和病死率逐渐上升。晚期结直肠癌的治疗中靶向治疗占有重要地位,而靶向药物出现耐药是结直肠癌治疗失败的主要原因。靶向药物耐药机制复杂,RAS、RAF突变等经典机制已被熟知,但具体机制尚未完全明确,因此研究其耐药机制以及如何阻断耐药是当下重点研究方向。本文主要综述几种靶向治疗药物在结直肠癌治疗中的耐药机制研究进展。     

西妥昔单抗联合化疗一线治疗KRAS/RAS野生型转移性结直肠癌的疗效及预后因素分析

目的探索影响西妥昔单抗联合化疗一线治疗KRAS/RAS野生型转移性结直肠癌的疗效和预后因素。方法回顾性分析155例接受西妥昔单抗联合化疗作为一线治疗方案的KRAS/RAS野生型转移性结直肠癌患者的病历资料,采用χ2检验或Fisher检验评估客观缓解率(ORR);采用Cox比例风险模型探讨KRAS/RAS野生型转移性结直肠癌患者预后的影响因素。结果西妥昔单抗联合化疗的中位治疗时间为18(6～26)周,一线治疗的ORR为60.1%,疾病控制率为92.2%。整体人群的中位随访时间为25.3(3.8～89.7)个月。一线治疗中位无进展生存期(PFS)为8.9个月(95%CI:7.9～9.9),中位总生存期(OS)为28.7个月(95%CI:23.6～33.8)。单因素分析结果显示:有腹膜转移、BRAF突变型、原发肿瘤未切除、转移灶未切除的KRAS/RAS野生型转移性结直肠癌患者的中位PFS短于无腹膜转移、BRAF野生型、原发肿瘤已切除、转移灶已切除的患者(P﹤0.05);原发肿瘤部位在右半结肠、有腹膜转移、BRAF突变型、原发肿瘤未切除、转移灶未切除的KRAS/RAS野生型转移性结直肠癌患者的中位OS短于原发肿瘤部位在左半结直肠、无腹膜转移、BRAF野生型、原发肿瘤已切除、转移灶已切除的患者(P﹤0.05)。多因素分析结果显示:BRAF突变型、原发肿瘤未切除是KRAS/RAS野生型转移性结直肠癌患者PFS的独立危险因素;有腹膜转移、BRAF突变型、转移灶未切除是KRAS/RAS野生型转移性结直肠癌患者OS的独立危险因素(P﹤0.05)。结论 BRAF突变和腹膜转移可能是西妥昔单抗联合化疗一线治疗KRAS/RAS野生型转移性结直肠癌预后的独立危险因素。原发肿瘤部位与OS相关,转移灶切除患者的PFS和OS均延长。     

RAS/RAF/丝裂原活化蛋白激酶/细胞外信号调节激酶信号通路在胃癌中的研究进展

胃癌（GC）的发病机制复杂,与多种因素有关,包括环境和遗传因素等。细胞内信号通路失调代表了一种常见的致病机制,可能适合对患者进行靶向药物治疗。RAS/RAF/丝裂原活化蛋白激酶（MEK）/细胞外信号调节激酶（ERK）信号通路在多种恶性肿瘤的发生发展中起到至关重要的作用。但迄今为止,大多数针对此通路的药物研究是基础实验,临床试验有待开展。本文就RAS/RAF/MEK/ERK信号通路在GC中的研究进展进行综述,重点论述其与GC的关系及潜在的作用机制,以及RAS/RAF/MEK/ERK信号通路抑制剂在GC治疗中的应用前景,旨在为GC的早期诊断和治疗提供新思路。     

伴有MSI的结直肠癌TGF-βRⅡ基因突变的研究

目的许多研究表明在伴有微卫星不稳定性(MicroSatellite Instability,MSI)的遗传性结直肠癌中,β-转化生长因子Ⅱ型受体(Transforming Growth Factor-β Type ⅡReceptor,TGF-β RⅡ)基因突变频繁,极可能是其发生的重要机制;并且TGF-RⅡ基因的(A)10重复序列是MSI的靶点.但在散发性结直肠癌中报道较少,本研究通过对散发性结直肠癌的MSI及TGF-RⅡ基因突变的检测,以期了解它们在散发性结直肠癌发生中的作用方法选取单态性很强的BAT-26微卫星位点,应用PCR等分子生物学手段检测MSI;应用PCR-SSCP-银染法-测序检测RⅡ基因突变结果有13例(26%)为MSI,近端(42.11%)明显高于远端者(16.13%)(P＜0.05),RⅡ基因的突变率为10%(5/50),表现为RⅡ基因的(A)10重复序列出现一个A的缺失导致框架移位突变(Frame Shift Mutation),伴有MSI的肿瘤中RⅡ突变率为38.46%,所有RⅡ突变者均伴有MSI,而无MSI的肿瘤中均无RⅡ突变(P＜0.01) 结论不仅在HNPCC中,而且在散发性结直肠癌中,TGF-βRⅡ基因的(A)10重复序列是MSI的靶点.     

与晚期结直肠癌EGFR单克隆抗体靶向药物选择相关的分子标志物

对于转移性结直肠癌而言,如何在标准化疗的基础上进行个体化靶向治疗是目前关注的热点。KRAS基因突变被认为是转移性结直肠癌对抗表皮生长因子受体(epidermal growth factor receptor,EGFR)单克隆抗体(anti-EGFR monoclonal antibody,anti-EGFR)靶向治疗反应不佳的独立预测因素。35%～45%的转移性结直肠癌患者存在KRAS基因的突变,且对anti-EGFR治疗抵抗;同时只有50%的野生型KRAS患者对anti-EGFR治疗有效,提示EGFR下游信号通路其他分子的激活和变异可能影响了其治疗反应。EGFR依赖的2条主要信号通路RAS-RAF-MAPK和PI3K-PTEN-AKT均与anti-EGFR治疗失败有关。EGFR基因拷贝数(gene copy number,GCN)增加与结肠癌anti-EGFR的疗效相关,但EGFR GCN增加并不意味着EGFR蛋白表达增加,且EGFR表达与anti-EGFR疗效无相关性。在野生型KRAS转移性结直肠癌患者中增加对BRAF和PIK3CA基因突变以及PTEN基因表达缺失的检测可能有助于筛选anti-EGFR抵抗患者。本研究对近年来转移性结直肠癌研究中所涉及的疗效预测和预后分子标志物进行综述,以进一步指导转移性结直肠癌的个体化分子靶向治疗。     

从分子分型演变看结直肠癌分子生物学行为

结直肠癌是一种异质性很强的肿瘤,肿瘤的异质性是肿瘤在发生发展过程中由基因突变、特征性遗传和表观遗传学改变等众多因素逐渐累积而成。根据肿瘤发生部位、染色体不稳定性、微卫星不稳定性、锯齿状通路改变以及DNA甲基化等因素对结直肠癌进行分子分型,以判断预后及指导治疗。本文回顾了近年来与结直肠肿瘤演进过程相关的分子分型的发展,结直肠癌有不同的分子亚群,而这些分子亚群通过不同的机制决定肿瘤的发生及发展,并与患者的预后密切相关。从分子分型的发展折射出对结直肠癌分子生物学行为的认知逐步深入,为结直肠癌的精准治疗奠定了基础。     

Treatment of Advanced BRAF-Mutated Colorectal Cancer: Where We Are and Where We Are Going

In recent years, studies on the molecular typing of colorectal cancer have matured, and the V-raf murine sarcoma viral oncogene homolog B (BRAF) of the mitogen-activated protein kinase pathway has been shown to be an important effector molecule of this pathway and regulates the occurrence and development of colorectal cancer. Clinical observations indicate that colorectal cancer patients harboring the BRAF V600E mutation have a worse prognosis than BRAF wild type patients. Several resistance mechanisms have been identified that have led to the development of different treatment strategies, which have shown encouraging activity in early clinical trials. Therefore, a reasonable combination of targeted therapies is expected to further enhance the efficacy of selective BRAF inhibitors. Moreover, some CRC patients with high microsatellite instability or a mismatch repair deficiency seem to be susceptible to checkpoint inhibitors with objective and sustained clinical responses, providing new opportunities for patients with advanced disease. This article primarily explores 3 aspects of the treatment strategies for advanced BRAF-mutated colorectal cancer; chemotherapy, targeted therapy, and immunotherapy.     

A Rare p.T599dup BRAF Mutant NSCLC in a Non-Smoker

V-RAF murine sarcoma viral oncogene homolog B1 (BRAF) mutated non-small-cell lung cancer (NSCLC) is an exceptionally rare form of lung cancer, found only in one to two percent of patients with an NSCLC diagnosis. BRAF NSCLC traditionally affects former or active smokers. BRAF mutations have always been of special interest to the oncological community, as they offer potential for targeted therapies. BRAF mutation spectrum includes mutations that are of both V600 and non-V600 types. BRAF V600 is an activating mutation, which results in high kinase activity and overproduction of active oncoproteins such as rapidly accelerated fibrosarcoma (RAF). This makes them susceptible to targeted therapies with RAF inhibitors. There has been little evidence, however, regarding efficacy of RAF inhibitors towards non-activating mutations that have intermediate to low kinase activity, such as non-V600 BRAF mutations. While several approaches have been investigated to overcome the limitations of RAF inhibitors, such as use of mitogen-activated protein kinase kinase (MEK) and extracellular signal-regulated kinase (ERK) inhibitors or combination of MEK and RAF inhibitors, none of them have been proven to have a superior efficacy for low kinase activity non-V600 BRAF tumors. We present a case of an extremely rare variant of NSCLC BRAF p.T599dup mutation in a non-smoker that responded to a targeted combination therapy with RAF and MEK inhibitors. The patient responded well to therapy that usually targets high kinase activity V600 mutations. Our hope is to bring more attention to non-V600 mutations and document their responses to existing and new therapies.     

First‐line therapy for metastatic colorectal cancer: Current perspectives and future directions

The prognosis for patients with newly diagnosed inoperable metastatic colorectal cancer has steadily improved over the past two decades as new agents have been introduced into clinical practice and many new biomarkers have been discovered. In parallel with this progress, clinicians face increasingly complex treatment decisions. This review summarizes recent progress, with a historical perspective, which should help guide the clinician in decision making and optimal therapy selection. This review not only focuses on important and readily identifiable subsets, including primary tumor side and v‐RAF murine sarcoma viral oncogene homologue B (BRAF) mutations, but also discusses rarer molecular subgroups that may be important for determining treatment in the future.     

基因检测指导下的晚期结直肠癌的个体化治疗

基于结直肠癌患者基因检测的个体化治疗可帮助临床医师获得最佳的治疗效果和最小的不良反应。晚期结直肠癌患者采用抗EGFR靶向治疗前,应检测RAS基因状态;对于拟采用含伊立替康方案化疗的结直肠癌患者,建议检测UGT1A1基因多态性;但BRAF突变、PIK3CA突变、ERCC1的mRNA表达等与药物疗效或毒性的相关性尚不明确。本文将与晚期结直肠癌治疗疗效或毒性相关的常见基因的分子检测分成强制检测、推荐检测和必要时检测三大类,帮助临床医生正确理解这些分子检测的实际价值,更好地为患者制定治疗方案。     

Protein kinase D3 sensitizes RAF inhibitor RAF265 in melanoma cells by preventing reactivation of MAPK signaling

RAS mutations occur in more than 30% of all human cancers but efforts to directly target mutant RAS signaling as a cancer therapy have yet to succeed. As alternative strategies, RAF and MEK inhibitors have been developed to block oncogenic signaling downstream of RAS. As might be expected, studies of these inhibitors have indicated that tumors with RAS or BRAF mutations display resistance RAF or MEK inhibitors. In order to better understand the mechanistic basis for this resistance, we conducted a RNAi-based screen to identify genes that mediated chemoresistance to the RAF kinase inhibitor RAF265 in a BRAF (V600E) mutant melanoma cell line that is resistant to this drug. In this way, we found that knockdown of protein kinase D3 (PRKD3) could enhance cell killing of RAF and MEK inhibitors across multiple melanoma cell lines of various genotypes and sensitivities to RAF265. PRKD3 blockade cooperated with RAF265 to prevent reactivation of the MAPK signaling pathway, interrupt cell cycle progression, trigger apoptosis, and inhibit colony formation growth. Our findings offer initial proof-of-concept that PRKD3 is a valid target to overcome drug resistance being encountered widely in the clinic with RAF or MEK inhibitors.     

EGFR-mediated re-activation of MAPK signaling contributes to insensitivity of BRAF mutant colorectal cancers to RAF inhibition with vemurafenib

BRAF mutations occur in 10-15% of colorectal cancers (CRCs) and confer adverse outcome. While RAF inhibitors such as vemurafenib (PLX4032) have proven effective in BRAF mutant melanoma, they are surprisingly ineffective in BRAF mutant CRCs, and the reason for this disparity remains unclear. Compared to BRAF mutant melanoma cells, BRAF mutant CRC cells were less sensitive to vemurafenib, and P-ERK suppression was not sustained in response to treatment. Although transient inhibition of phospho-ERK by vemurafenib was observed in CRC, rapid ERK re-activation occurred through EGFR-mediated activation of RAS and CRAF. BRAF mutant CRCs expressed higher levels of phospho-EGFR than BRAF mutant melanomas, suggesting that CRCs are specifically poised for EGFR-mediated resistance. Combined RAF and EGFR inhibition blocked reactivation of MAPK signaling in BRAF mutant CRC cells and markedly improved efficacy in vitro and in vivo. These findings support evaluation of combined RAF and EGFR inhibition in BRAF mutant CRC patients. SIGNIFICANCE: BRAF valine 600 (V600) mutations occur in 10% to 15% of colorectal cancers, yet these tumors show a surprisingly low clinical response rate (~5%) to selective RAF inhibitors such as vemurafenib, which have produced dramatic response rates (60%–80%) in melanomas harboring the identical BRAF V600 mutation. We found that EGFR-mediated MAPK pathway reactivation leads to resistance to vemurafenib in BRAF-mutant colorectal cancers and that combined RAF and EGFR inhibition can lead to sustained MAPK pathway suppression and improved efficacy in vitro and in tumor xenografts.     

The “SWOT” of BRAF Inhibition in Melanoma: RAF Inhibitors,MEK Inhibitors or Both?

Activating mutations in the BRAF gene are among the most prevalent kinase mutations in human cancer. BRAF mutations are most frequent in patients with melanoma where they occur in approximately 50% of patients with advanced disease. Remarkable clinical activity has recently been reported with highly selective RAF inhibitors in melanoma patients whose tumors harbor V600E BRAF mutations. The response rates of RAF inhibitors in patients with BRAF-mutant melanomas far exceed the activity level of any prior therapy studied in this disease. The results suggest that we have entered an era of personalized therapy for patients with metastatic melanoma in which treatment selection will be guided by BRAF mutational status. This review will discuss the strengths, weaknesses, opportunities and threats ("SWOT") of developing RAF and MEK selective inhibitors as anti-cancer therapies, recent insights into the mechanisms of intrinsic and acquired resistance to these agents, and current efforts to develop mechanism-based combination therapies.     

Raf kinases in cancer-roles and therapeutic opportunities

Raf are conserved, ubiquitous serine/protein kinases discovered as the cellular elements hijacked by transforming retroviruses. The three mammalian RAF proteins (A, B and CRAF) can be activated by the human oncogene RAS, downstream from which they exert both kinase-dependent and kinase-independent, tumor-promoting functions. The kinase-dependent functions are mediated chiefly by the MEK/ERK pathway, whose activation is associated with proliferation in a broad range of human tumors. Almost 10 years ago, activating BRAF mutations were discovered in a subset of human tumors, and in the past year treatment with small-molecule RAF inhibitors has yielded unprecedented response rates in melanoma patients. Thus, Raf qualifies as an excellent molecular target for anticancer therapy. This review focuses on the role of BRAF and CRAF in different aspects of carcinogenesis, on the success of molecular therapies targeting Raf and the challenges they present.     

PI3K and MEK inhibitor combinations: examining the evidence in selected tumor types

The PI3K/AKT/mTOR and RAS/RAF/MEK/ERK pathways are two of the most frequently dysregulated kinase cascades in human cancer. Molecular alterations in these pathways are implicated in tumorigenesis and resistance to anticancer therapies. The PI3K/AKT/mTOR and RAS/RAF/MEK/ERK pathways are known to interact with each other at several nodes, and mounting evidence suggests that dual blockade of both pathways may be required to achieve anticancer effects in certain contexts. This may include tumor types with a high frequency of RAS/RAF/MEK/ERK pathway activation, or situations in which dual pathway strategies may be required to overcome resistance to current targeted therapies. Several clinical studies are currently evaluating the combination of PI3K and MEK inhibitors in a variety of different cancers with certain types of molecular alterations. This review will summarize existing knowledge of the PI3K/AKT/mTOR and RAS/RAF/MEK/ERK pathways, the cross-talk between them, and the current generation of PI3K and MEK inhibitors that target them. The preclinical rationale for dual pathway inhibition will be discussed within the context of the major tumor types currently being explored in ongoing clinical trials, namely malignant melanoma with BRAF or NRAS mutations, and colorectal, ovarian, pancreatic, and basal-like breast cancers. The emerging clinical profile of PI3K and MEK inhibitor combinations, as reported in Phase I trials, will also be discussed.     

非小细胞肺癌靶向治疗研究进展

研究发现非小细胞肺癌与多种致癌突变密切相关,如表皮生长因子受体突变、间变性淋巴瘤激酶重排以及肝细胞生长因子受体扩增等。本文从腺癌和鳞状细胞癌两个亚型入手,分别介绍了非小细胞肺癌潜在的分子靶点及其抑制剂,包括EGFR抑制剂、ALK抑制剂、ROS1抑制剂、c-MET抑制剂、RAS抑制剂、BRAF抑制剂、HER-2抑制剂、NTRK1抑制剂、RET抑制剂、MEK1抑制剂、PI3K抑制剂、FGFR1抑制剂、DDR2抑制剂及IGF-1R抑制剂。为非小细胞肺癌患者临床用药和靶向治疗药物开发提供参考。