Molecular characteristics for poor prognosis related renal cell carcinoma with lymph metastases

  • Fan SHU 1, 2 ,
  • Liyuan GE 1 ,
  • Hanzhang DENG 1, 3 ,
  • Haoming YIN 1 ,
  • Junyong OU 1 ,
  • Shaohui DENG 1 ,
  • Yichang HAO 1 ,
  • Min LU 4, 5 ,
  • Zhanyi ZHANG 1 ,
  • Peichen DUAN 1 ,
  • Shudong ZHANG , 1, *
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  • 1. Department of Urology, Peking University Third Hospital, Beijing 100191, China
  • 2. Department of Urology, The Second Affiliated Hospital of Kunming Medical University, Kunming 650101, China
  • 3. Center for Biomarker Discovery and Validation, National Infrastructures for Translation Medicine, Institute of Clinical Medicine, Peking Union Medical College Hospital, Beijing 100730, China
  • 4. Department of Pathology, Peking University Third Hospital, Beijing 100191, China
  • 5. Department of Pathology, Peking University School of Basic Medical Sciences, Beijing 100191, China
ZHANG Shudong, e-mail,

Received date: 2024-07-10

  Online published: 2026-01-07

Supported by

the National Natural Science Foundation of China(82273389)

the Natural Science Foundation of Beijing(7232212)

Copyright

All rights reserved. Unauthorized reproduction is prohibited.

Abstract

Objective: Next-generation sequencing (NGS) technology was used to analyze the gene mutation profile of lymph node metastases in renal cell carcinoma, and the molecular characteristics associated with poor prognosis were found, providing new ideas for mechanism research and treatment. Methods: Retrospective clinical data collection was conducted on 31 patients with lymphoid metastatic renal cell carcinoma and 21 patients with non-metastatic renal cell carcinoma. A total of 81 formalin-fixed paraffin-embedded tissue samples were retrieved from the Department of Pathology, including primary tumor, lymph node metastasis, and distant metastasis samples. The gene mutation profiles of the patients were examined using next-generation sequencing technology. The patients were followed up to analyze the correlation between lymph node metastasis and patient prognosis. Results: The lymph node metastasis group showed differences in tumor size (P=0.006), World Health Organization (WHO)/International Society of Urological Pathology (ISUP) grade (P=0.002), T stage (P=0.003) and tumor thrombus (P=0.025) compared with non-metastatic renal cell carcinoma. The most commonly mutated genes in our cohort were the tumor suppressor genes VHL (38%), PBRM1 (22%), and SETD2 (20%). More-over, copy number variations were associated with tumor metastasis, and some mutation features were highly similar to known mutation patterns. There was a difference in mutation frequency between the patients in the metastasis group and samples in the non-metastasis group. The mutation frequency of most genes in the metastasis group was higher, however, Reactome pathway enrichment analysis did not show statistically significant differences in the shared enriched pathways between the two groups. There was a strong degree of concordance between the tumor' s primary and metastatic foci in the same patient, and genomic indicators [such as purity, ploidy, weighted-genomic integrity index (WGII), and intra-tumor heterogeneity (ITH)] as well as clonal and subclonal composition analysis further supported this consistency. The overall survival (OS) was higher in the patients without metastases (P=0.041), and specific gene mutations (such as IGF2R, JUN, EPHA5, and FH) were associated with poorer prognosis. To facilitate distant metastasis, lymph nodes might function as a "metastatic pool". Conclusion: The multigene NGS evaluates multiple relevant markers simultaneously, revealing several genetic alterations in the patients with lymphatic metastatic renal cell carcinorma. NGS-based molecular analysis can assist clinicians in assessing a patient' s prognosis and identifying novel, potentially therapeutic mechanisms.

Cite this article

Fan SHU , Liyuan GE , Hanzhang DENG , Haoming YIN , Junyong OU , Shaohui DENG , Yichang HAO , Min LU , Zhanyi ZHANG , Peichen DUAN , Shudong ZHANG . Molecular characteristics for poor prognosis related renal cell carcinoma with lymph metastases[J]. Journal of Peking University(Health Sciences), 2026 , 58(3) : 631 -640 . DOI: 10.19723/j.issn.1671-167X.2026.03.025

肾细胞癌(renal cell carcinoma, RCC,简称肾癌),占所有成人恶性肿瘤的2%~3%,是肾脏最常见的恶性肿瘤[1]。近年来随着诊断技术尤其是影像学的发展,很多小肾癌在早期被检出,但仍有相当数量的患者确诊时即为局部晚期,甚至高达17%的患者有远处转移[2]。肾癌的转移途径之一是淋巴转移,可能与患者预后差以及生存率低有关[3]。肾癌对放疗和化疗不敏感,手术切除是目前最推荐的治疗方法[4]。一些淋巴结转移的患者即使在接受了淋巴结清扫(lymph node dissection, LND)治疗后仍会出现复发或转移,因此关于LND在肾癌中的治疗价值仍在争论中[5]
目前,转移性肾癌患者的治疗方案很少,而且尚不清楚是什么原因导致了淋巴结转移[6],因此,为了更好地治疗预后不良和有淋巴结转移的肾癌患者,了解淋巴结转移的机制并发现新的生物标志物是当务之急[7]。既往有研究阐述了无转移的原发性肾癌的基因组图谱,但对于特定类型的淋巴转移性肾癌,相关的分子分析研究较少[7]。本研究探讨与淋巴转移性肾癌预后不良相关的基因模式,并将其作为评估工具确定潜在的靶点,以开发新的诊断和治疗方法。

1 资料与方法

1.1 资料收集

本研究选择了52例确诊为肾癌的患者,从北京大学第三医院泌尿外科的自建数据库中提取患者的相关临床资料,包括人口统计学资料(年龄、性别、体重指数、吸烟史、饮酒史、高血压)、肿瘤特征(T分期、肿瘤大小、合并癌栓)、血清学指标(血尿素氮、血红蛋白、肌酐)和病理特征[世界卫生组织(World Health Organization,WHO)/国际泌尿病理协会(International Society of Urological Pathology, ISUP)分级、病理类型]。从病理科调取甲醛溶液固定的石蜡包埋组织,包括肿瘤的原发灶和转移灶,进行下一代测序(next-generation sequencing, NGS),通过靶向人类基因组上808个基因外显子区域的测序基因检测芯片检测基因突变情况。从52例患者中获取原发灶及转移灶共81个组织样本进行NGS测序,在31例转移性肾癌中,5例患者仅获取到原发灶样本,26例患者获得了配对的原发灶和转移灶样本,所有患者均有淋巴结样本,另有2例获取了骨转移灶样本,1例获取了肝转移灶样本。

1.2 基因组DNA提取及NGS测序

根据患者对应的病理号从病理科调取石蜡包埋组织切片,由泌尿生殖病理学家对苏木精-伊红(hematoxylin-eosin,HE)染色的切片进行组织学分析,以确认样本中存在足够的肿瘤组织。将样本送往北京橡鑫生物科技有限公司进行测序分析,从切片中去除多余的石蜡,使用QIAamp DNA石蜡包埋试剂盒(德国Qiagen公司)从所有研究样本中提取DNA,操作步骤严格按照试剂盒说明进行。用Qubit dsDNA HS Assay试剂盒(美国Thermo Fisher公司)和Qubit 4.0荧光定量分析仪测定提取成功的DNA浓度,进一步通过聚丙烯酰胺凝胶电泳法测定DNA的降解程度。使用Covaris E210仪器(美国Covaris公司)将100 ng基因组DNA剪切到200 bp的目标片段大小,使用KAPA Hyper Library试剂盒(美国Kapa BiosSystems公司)制备文库,根据说明,利用定制的NGS Panel对包含与肾癌相关的基因(热点、选定外显子或完整编码序列)索引库进行基于探针的杂交,实现靶标捕获。在Illumina Nextseq CN500平台(美国Illumina公司)上,以95%的捕获率和40%的重复率对样品进行测序,读取长度为150 bp,平均覆盖率为1 000倍。
原始数据经过筛选后进行生物信息学分析,检测的遗传变异类型包括融合变异、点突变、插入缺失变异和拷贝数变异,以GRCH37/hg19为参考序列。如果基因突变丰度为1%或更高,则定义为阳性。肿瘤基因组编码区在去除胚系突变后,每Mb的体细胞突变数定义为肿瘤突变负荷(tumor mutation load, TMB)。使用CONTRA(2.1.0版)软件进行拷贝数变异(copy number variation, CNV)分析,对每个碱基取对数以及均一化测序读段,从而消除GC含量的影响。

1.3 KEGG通路富集分析

为探索目标基因集在生物学通路中的潜在功能,本研究使用R语言中的clusterProfiler包进行京都基因与基因组百科全书(Kyoto Encyclopedia of Genes and Genomes, KEGG)通路富集分析。提取显著差异表达或变异的基因列表作为输入的目标基因集,通过Fisher精确检验评估基因集是否在KEGG通路数据库中的某些通路中富集,并计算每条通路的富集显著性P值,校正后的P值用于确定显著富集的通路。对于显著富集的通路,进一步分析其生物学意义。

1.4 克隆进化模式的定义

为了研究肿瘤的进化,参考TRACERx研究[8]中描述的方法分析克隆进化模式,根据原发肿瘤和转移瘤的克隆/亚克隆组成情况分为选择性克隆、非选择性克隆、克隆维持三种状态。选择性事件被定义为在原发灶中缺失但存在于转移灶中的克隆/亚克隆,或原发灶中存在的亚克隆在转移灶中表现为克隆的模式。非选择性事件定义为原发灶中的克隆/亚克隆在转移灶中缺失。维持事件被认为是最近共同祖先,即在原发灶和转移灶中都为克隆或亚克隆的模式;另外,在原发灶中为克隆,转移灶中为亚克隆的也归为此类。

1.5 系统发育树的构建

为表征既有淋巴结转移又伴随远处转移患者的特定肿瘤进化模式,我们构建了基于体细胞突变数据的系统发育树。先提取样本中的体细胞突变数据,计算每个突变位点的变异等位基因频率(variant allele frequency, VAF),并使用该频率作为肿瘤克隆的代表性特征之一。为提高数据的准确性,根据体细胞拷贝数变异信息校正VAF值,以校准样本中不同肿瘤细胞群体的读取深度。随后基于校正后的VAF构建系统发育树,以此重建肿瘤细胞的进化历史。系统发育树的构建采用最大似然法,并使用Bootstrapping方法对树的可靠性进行评估。

1.6 统计学分析

使用GraphPad Prism 7.10和R 4.2.2软件进行统计分析。分类变量用频率和百分比表示,正态分布的连续变量以均值±标准差表示,非正态分布的连续变量以中位数(四分位数)表示。使用Wilcoxon秩和检验或非配对t检验评估两组连续变量之间的差异,以Kruskal-Wallis H检验或单因素方差分析评估三组及以上连续变量之间的差异,以卡方检验或Fisher精确检验分析不同组之间在基因特征和临床病理特征等分类变量上的差异,对于有序分类变量,采用Kruskal-Wallis H检验。采用Spearmann相关系数评价变量间的相关性,使用Kaplan-Meier方法统计患者的总生存期(overall survival, OS),OS定义为从手术日期到出现结局的日期或最后一次随访的日期,评估的主要结局是死亡。根据结局事件的发生情况将患者分为两组,即随访期间死亡的患者(Group 1)以及最后一次随访时仍存活的患者(Group 2),分别代表预后好与预后差。P<0.05为差异有统计学意义。

2 结果

2.1 患者的人口统计学和临床基线特征

表 1总结了52例患者的临床特征,其中淋巴结转移性肾癌31例,非转移性肾癌21例。初步分析显示,较大的肿瘤(8.2 cm vs. 4.6 cm,P=0.006)、较高的WHO/ISUP分级(0.002)、较高的T分期(P=0.003)以及合并癌栓(P=0.025)与肿瘤淋巴结转移呈显著相关。性别、年龄、体重指数、高血压、吸烟、饮酒、血尿素氮、肌酐和病理类型在两组间差异无统计学意义。
表1 淋巴结转移性肾细胞癌组和非转移组患者的人口统计学和临床基线特征

Table 1 Demographic and clinical characteristics between lymphoid metastatic renal cell carcinoma group and non-metastatic group

Variable Overall Metastatic group Non-metastatic group P value
Number of patients 52 31 21
Gender, n (%) >0.999
  Female 19 (36.5) 11 (35.5) 8 (38.1)
  Male 33 (63.5) 20 (64.5) 13 (61.9)
T stage, n (%) 0.003
  Tx 2 (3.8) 2 (6.5) 0 (0)
  T0 2 (3.8) 0 (0) 2 (9.5)
  T1 14 (26.9) 3 (9.7) 11 (52.4)
  T2 2 (3.8) 1 (3.2) 1 (4.8)
  T3 29 (55.8) 22 (71.0) 7 (33.3)
  T4 3 (5.8) 3 (9.7) 0 (0)
Smoking, n (%) 0.325
  No 35 (67.3) 23 (74.2) 12 (57.1)
  Yes 17 (32.7) 8 (25.8) 9 (42.9)
Drinking, n (%) 0.415
  No 39 (75.0) 25 (80.6) 14 (66.7)
  Yes 13 (25.0) 6 (19.4) 7 (33.3)
Hypertension, n (%) 0.367
  No 27 (51.9) 14 (45.2) 13 (61.9)
  Yes 25 (48.1) 17 (54.8) 8 (38.1)
Pathological type, n (%) 0.293
  ccRCC 34 (65.4) 18 (58.1) 16 (76.2)
  nccRCC 18 (34.6) 13 (41.9) 5 (23.8)
WHO/ISUP grade, n (%) 0.002
  1 1 (1.9) 1 (3.2) 0 (0)
  2 17 (32.7) 3 (9.7) 14 (66.7)
  3 22 (42.3) 18 (58.1) 4 (19.0)
  4 12 (23.1) 9 (29.0) 3 (14.3)
Tumor thrombus, n (%) 0.025
  No 34 (65.4) 16 (51.6) 18 (85.7)
  Yes 18 (34.6) 15 (48.4) 3 (14.3)
Age/years, M (P25, P75) 53.50 (43.00, 63.25) 53.00 (46.00, 63.50) 58.00 (43.00, 61.00) 0.867
Tumor size/cm, M (P25, P75) 6.70 (4.42, 9.93) 8.20 (5.85, 10.60) 4.60 (2.60, 6.50) 0.006
BMI/(kg/m2), M (P25, P75) 24.44 (21.96, 26.09) 24.44 (20.92, 26.02) 24.42 (23.51, 26.12) 0.396
Hemoglobin/(g/L), M (P25, P75) 133.50 (112.00, 150.25) 128.00 (112.00, 137.00) 151.00 (132.00, 162.00) 0.002
BUN/(mmol/L), M (P25, P75) 5.25 (4.38, 6.00) 5.55 (4.80, 6.25) 4.80 (4.00, 5.70) 0.097
Creatinine/(μmol/L), M (P25, P75) 80.50 (71.25, 102.25) 84.00 (71.00, 116.50) 78.00 (72.00, 85.00) 0.138

ccRCC, clear cell renal cell carcinoma; nccRCC, non-clear cell renal cell carcinomas; WHO/ISUP, World Health Organization/International Society of Urological Pathology; BMI, body mass index; BUN, blood urea nitrogen.

2.2 总体样本的基因组特征

所有样本的体细胞突变情况如图 1A所示,该队列中最常见的突变基因是肿瘤抑制基因VHL (38%)、PBRM1 (22%)和SETD2 (20%),其他高频突变基因包括FAT1 (15%)和KMT2D (15%)。错义突变占体细胞突变的大部分,有很高比例的无义突变和移码缺失突变,尤其是在SETD2PBRM1中更为显著。将此结果与癌症基因组图谱(The Cancer Genome Atlas, TCGA)里的肾透明细胞癌(kidney renal clear cell carcinoma,KIRC)数据集进行比较,以找出这些突变频率是否与早期研究不同。TCGA-KIRC的相关结果为VHL 49.9%、PBRM1 30.6%、SETD2 11.3%,与本研究的结果存在差异。
图1 所有肾细胞癌样本的基因突变谱

Figure 1 Molecular profile of all renal cell carcinoma samples

A, whole exome sequencing revealed the somatic mutations that were most frequent in our cohort. Patients are displayed individually in the columns (grey squares), with colored squares denoting the presence of somatic mutations. B, the copy number variants (CNVs) that are prevalent in this cohort. M, metastatic group; NM, non-metastatic group.

图 1B所示,在30个样本(37.0%)中发现基因组大片段的拷贝数增加或者减少,最常见的CNV是MCL1 (10%)和GNA13 (8%)拷贝数增加,CARM1 (8%)和CDKN2A (8%)拷贝数减少(在此基础上,CARM1CDKN2A各有1%的拷贝数增加),后续的分析中发现,这些样本的CNV特征似乎与肿瘤的转移有关。

2.3 淋巴结转移性肾癌与非转移性肾癌的比较

淋巴结转移性和非转移性肾癌患者的体细胞突变谱见图 2AB。在非转移性肾癌中,最常见的突变是VHL (62%)、PBRM1 (24%)、NCOR2 (19%)、UPF1 (19%)、KMT2C (14%)和LRP1B (14%)。在淋巴结转移性肾癌中,最常见的突变是VHL (35%)、PBRM1 (29%)、SETD2 (29%)和FAT1 (19%)。非转移组中VHL (62%)、PBRM1 (24%)、NCOR2 (19%)和UPF1 (19%)突变频率较高。此外,对两组中前20个CNV的分析显示,大多数基因片段在淋巴结转移组中有更大的变异,其中很大一部分只出现在淋巴结转移组中(图 2C)。
图2 转移性与非转移性肾细胞癌体细胞突变的基因图谱

Figure 2 The genomic landscape of somatic mutations in renal cell carcinoma with or without lymphoid metastasis

A, oncoprint illustrations of somatic alterations in nonmetastatic RCC by gene frequency; B, oncoprint illustrations of somatic alterations in metastatic RCC by gene frequency; C, the top 20 differential CNV between metastatic and nonmetastatic ccRCC patients; D, KEGG analysis of mutated genes with different prevalence in the nonmetastatic group; E, KEGG analysis of mutated genes with different prevalence in the metastatic group. RPSC signaling pathway: signaling pathways regulating pluripotency of stem cells. RCC, renal cell carcinoma; ccRCC, clear cell renal cell carcinoma; CNV, copy number variants; Padj, adjusted P value; KEGG, Kyoto Encyclopedia of Genes and Genomes.

KEGG通路富集分析表明,非转移组的突变基因在HIF-1、ErbB、FoxO、mTOR和PI3K-Akt信号通路上富集(图 2D),淋巴结转移组的特征是在Rap1、Thyroid hormones、Fanconi和RAS信号通路上富集(图 2E),然而对两组共有的富集途径进行统计分析,未发现两组差异有统计学意义。

2.4 肾癌原发灶和淋巴结转移灶之间的基因突变差异

图 2B图 3A所示,在原发灶的前20个差异基因和淋巴结转移灶的前20个差异基因里,有9个基因是存在交集的,此外,VHLSETD2FAT1均出现在两组排名的前5,表明淋巴结转移性肾癌患者的肿瘤原发灶和转移灶基因突变频率在原发肿瘤和转移瘤之间表现出很强的一致性。其他指标也支持这一结果,如纯度、倍性、加权基因组完整性指数(weighted-genomic integrity index, WGII)和肿瘤内异质性(intra-tumor heterogeneity, ITH)的差异没有统计学意义(图 3B~E)。利用基于肿瘤的基因组测序数据对克隆和亚克隆的组成进行分析表明,原发灶和淋巴结转移灶在体细胞基因突变水平和染色体臂级水平的CNV上的组成相似(图 3FG)。
图3 转移性肾细胞癌原发灶和转移灶的差异突变模式

Figure 3 Discordance of mutation patterns between primary and metastatic renal cell carcinoma

A, oncoprint illustrations of somatic alterations in metastasis by gene frequency. B-E, four box plots summarizing: purity, ploidy, weighted-genomic integrity index (WGII), and intra-tumor heterogeneity (ITH). Values are compared between primary and metastatic tumors, and the P value is at the top of the plot. F, composition of clonal and subclonal arms alterations in the primary and metastatic tumors. G, composition of clonal and subclonal somatic alterations in the primary and metastatic tumors.

2.5 转移驱动因素分析

根据原发肿瘤和转移瘤的克隆和亚克隆组成情况定义克隆进化模式(图 4A),进一步分析来自不同患者的配对病灶中选择性克隆的占比情况,即各病灶特有的选择性克隆和配对病灶共有的选择性克隆之间的分布(图 4B)。
图4 肾细胞癌原发灶和转移灶之间的克隆进化特征

Figure 4 Characterization of metastasizing clones between primary and metastatic renal cell carcinoma

A, illustration of the method used to categorize tumor clones. B, shared and private mutations among the paired primary and metastatic samples. Every column represents a patient and the height of the column depicts the percentage of mutations in that pair. C, the selection of alterations between primary tumor and metastasis, the bar chart demonstrates the percentage of mutation clonal genes. D, the selection of alterations between primary tumor and metastasis, the bar chart demonstrates the percentage of arm-level clone.

在基因水平上,我们发现PPRSSRDAXXPTEN的选择性克隆的差异有统计学意义(图 4C);而在染色体臂级水平上,我们发现4P_LOSS、4Q_LOSS和6P_GAIN的选择性克隆的差异有统计学意义(图 4D)。在TCGA数据库中进一步验证上述三个基因在原发灶和转移灶中的差异,除了PTEN外,其余均没有统计学意义。

2.6 肾癌的淋巴结转移分析

分析有淋巴结转移和无淋巴结转移组患者的预后差异(图 5A),生存曲线显示,无淋巴结转移组患者的OS较高(P=0.041)。淋巴结转移组患者的1、2、3年生存率分别为86.7%、78.1%、52.9%,明显低于无淋巴结转移组的100.0%、91.2%、82.6%。根据本研究方法部分所定义的分组方法,分析预后好与预后差两组患者之间的突变差异(图 5B),ARID1BDNMT3AEPHA5FHGRIN2AIGF2R突变在Group 2(最后一次随访时仍存活的患者)中占比较高,而DNMT1HLA-AJUN突变在Group 1(随访期间死亡的患者)中占比更高。通过TCGA数据库进一步分析发现,IGF2R与更好的无病生存期(disease-free survival, DFS)显著相关,JUN与较差的DFS显著相关,EPHA5FH与较差的OS显著相关,其余基因与预后的关联无统计学意义。
图5 肾细胞癌淋巴结转移与预后的关联分析

Figure 5 Correlation analysis between lymph node metastasis and prognosis in renal cell carcinoma

A, Kaplan-Meier curve showing the overall survival (OS) to time of death compared by lymphatic metastasis via the Log-rank test. Patients lost to follow-up were censored from analysis and are represented by the tick marks on the curves. B, the frequency of genes with different prevalence between different prognostic groups. Group 1 represented the population in which an outcome event (death) occurred during follow-up. Group 2 represented the patients who were still alive at the last follow-up. C-D, lymph nodes act as a "metastatic pool" to support distant metastasis of the tumor. C, molecular evolution in a typical renal cell carcinoma patient with both lymph node and bone metastases, and the number of mutations determines the length of the corresponding branch and trunk. D, venn diagram illustrated the overlap and independently mutated genes between the primary tumor, lymph node and bone metastases.

在同时伴有淋巴结和远处器官转移的病例中,对原发灶、淋巴结转移灶和远处转移灶的样本都进行了NGS测序以分析疾病的克隆进化演变。在1例典型的患者中,我们发现病理性淋巴结和肿瘤转移灶在克隆进化上非常接近,淋巴结可以作为“转移池”,支持肿瘤的远处转移(图 5CD),进一步分析显示,在原发灶、转移灶和病理性淋巴结样本中发现了NF2驱动基因的突变。

3 讨论

以往一些对于原发肾癌分子特征的分析研究改变了人们对驱动癌症的生物学机制的理解[9-11]。尽管已经开发了各种治疗方法,但肾癌仍然出现复发、进展到更高分期甚至转移。为了确定治疗靶点和改善患者预后,有必要从分子生物学角度探索原发灶和转移灶之间的区别[12]。既往有研究发现,淋巴结转移可增加远处转移的风险[13],并且对患者的存活率有显著影响[14]。因此,了解与预后不良相关的分子特征可能有助于改善患者的治疗和预后,这项研究可以视为对TRACERx研究[8]和许多其他研究报道的关于肾癌基因组图谱的补充。根据分析结果,本研究中该队列具有与已知数据库相似的突变基因及频率,不同点在于,本研究聚焦于分析不同预后的淋巴结转移患者,最终发现,包括ARID1BDNMT3AEPHA5FHGRIN2AIGF2RDNMT1HLAAJUN在内的点突变可能在影响患者预后中起重要作用。
本研究分析发现,TCGA-KIRC数据集中VHLPBRM1的突变频率总体上高于我们的队列,考虑到TCGA-KIRC数据集仅包括透明细胞肾癌患者,而我们的队列包含了不同亚型的转移性肾癌,这种差异可能反映了不同亚型的突变特征差异。此外,种族差异也可能导致突变频率上的偏差。SETD2在我们的队列中突变频率高于TCGA-KIRC数据集,这可能表明其在转移性肾癌中的独特作用。SETD2突变已知与染色质修饰相关,其突变可能引起基因组不稳定性,促进癌症进展和转移。与SETD2突变相关的高频无义突变和移码缺失突变提示,该基因的功能性缺失可能对肾癌的进展产生更为深远的影响,特别是在转移性疾病的背景下。
通过对TCGA数据库的分析,我们发现DNMT1DNMT3A的差异没有统计学意义,但在本研究的队列中,这两个基因显示出较高的TMB。该类基因属于DNA损伤修复基因,可能对免疫检查点抑制剂治疗或化疗有反应,在某些疾病(例如乳腺癌[15]和胰腺癌[16])中,这类基因已被视为治疗的靶标。目前国内关于这两个基因在肾癌中的研究较少,部分研究发现,DNMTs在肾癌中的表达量高于非肿瘤组织[17],且其表达与较短的OS和DFS显著相关[18]。本研究发现,IGF2R突变与较好的预后显著相关;既往研究认为,IGF2R突变与肿瘤微环境的改变有关[19]。一项关于肺癌的报道指出,Trop2IGF2R结合促进IGF2-IGF1R-Akt轴,从而增强非小细胞肺癌对吉非替尼的耐药性,并重塑肿瘤微环境[20]
我们发现,随访期间出现死亡的患者群体中EPHA5的突变率较高,TCGA数据库分析提示,该基因与更差的肾癌预后有关。既往关于肺腺癌组织的研究发现,EPHA5的表达与淋巴结转移和EGFR突变有关[21],并且在一定程度上可能预测肺腺癌免疫治疗后的存活率[22]EPHA5基因已被证实可通过激活Wnt/β-catenin通路,促进上皮间质转化增强肿瘤的侵袭和迁移能力[23]FH是编码线粒体三羧酸循环中延胡索酸水化酶的一个基因,位于1号染色体(1q42),是从遗传性平滑肌瘤病肾癌患者中发现的[24]FH体系突变同样可能导致肾癌发生,且与FH胚系突变导致的遗传性平滑肌瘤病肾癌具有极其相似的生物学行为[25]。本研究发现,FH突变与肾癌淋巴结转移的预后有关,或许该基因可以作为改善此类患者生存结局的靶点。
既往研究已经发现,淋巴结转移是肾癌合并癌栓患者预后不良的先兆,5年生存率不到1/3[26]。本研究发现,肾癌伴淋巴结转移的患者预后明显较差。然而,由于随访时间有限,我们没有获得5年生存率的数据,在本研究队列中,3年生存率约为50%。在分析患者的临床特征时,我们发现肿瘤大小、T分期、WHO/ISUP分级和伴有癌栓与淋巴结转移有关,这与以往的研究结果一致[27-29]。一项研究认为,肿瘤直径大于7 cm的患者有更高的淋巴结转移风险[29]。根据Zheng等[28]的研究结论,更高的T分期和M分期与肾癌患者的生存不良有关,并且是淋巴结转移的独立预测因素。在本研究中,确实发现T分期与淋巴结转移密切相关,但由于数据量和样本量有限,仅有3例远处转移病例,因此无法验证M分期与淋巴结转移的关系。此外,Pantuck等[27]的研究指出,Fuhrman分级高(3~4级)的肿瘤更有可能出现淋巴结转移,概率可达26%,但在1~2级的肿瘤中,该值仅为6%。
肿瘤恶性进展是一个动态的进化过程,有研究试图探索肿瘤在不同阶段的遗传特征,区分恶性进展过程中的早期或晚期事件,并试图分析基因变异结构以解释肿瘤细胞如何在转移过程中逃避免疫监视[30]。我们利用有限数量的患者,将来自不同转移部位的配对肿瘤样本进行克隆进化研究,发现肾癌骨转移灶和病理性淋巴结在突变水平上具有共同的祖先,同时又具有各自的特点,并鉴定出NF2突变作为驱动基因支持淋巴结转移和远处转移。NF2是Ⅱ型神经纤维瘤病的关键基因,作为一种抑癌因子,在很多脑瘤中表达缺失,并且其编码Merlin蛋白功能的缺失是造成肿瘤发生、发展的重要因素[31]。然而,NF2与肾癌的关系目前尚不清楚,仅少数研究报道了在一些特定的肾癌亚型中发现了涉及NF2的双等位基因变异,并且可能与更具侵袭性的疾病过程以及晚期表现有关[32-33]
本研究存在一定局限性,首先,对26例淋巴结转移的肾癌患者进行了回顾性分析,难免存在选择偏倚;其次,性别、年龄和治疗方式等临床指标没有完全随机,这可能会导致混杂因素的影响;第三,由于随访结束时患者的累积存活率大于50%,因此无法得出准确的中位OS,但可以知道的是,该值大于31个月;第四,来自不同患者的转移样本是在整个病程中不同时间点获得的,并且只在肿瘤的一个区域进行取材做基因测序,这可能会限制我们对原发病肿瘤和转移病变之间在时间和空间一致性上的分析;最后,肾癌的不同病理类型在分子特征、突变谱和生物学行为方面存在比较明显的差异,而本文在研究设计之初纳入样本时未考虑自然状态下病理类型的占比,纳入非透明细胞肾癌的比例较高(34%),可能会导致结果的偏差和误解。

利益冲突  所有作者均声明不存在利益冲突。

作者贡献声明  舒帆、葛力源:研究设计,数据整理,论文撰写;邓汉彰、邓绍晖、殷昊明:研究设计和指导;欧俊永、陆敏、郝一昌:论文修改,研究设计;张展奕、段佩辰:数据收集,统计学分析;张树栋:研究设计,论文修改,总体把关和审定论文。所有作者均参与论文修改,并对最终文稿进行审读和确认。

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