《癌细胞》：肾癌免疫疗法研究进展

编辑翻译：菁菁

译文校对：奇奇

文献在2021年3月最新的美国生物医学学术期刊《癌细胞》首次刊发。文献中研究人员使用了单细胞RNA测序技术描述肾脏肿瘤的微环境如何响应免疫疗法，为新的药物疗法提供了潜在靶点。

在过去的二十年中，免疫治疗已成为晚期肾癌的主要治疗方法。免疫疗法被包括在肾癌护理标准中，但不适应于所有患者。无论患者最初的反应如何，随着时间流逝，几乎所有患者对治疗的抗药性都会越来越强。免疫系统在患者的肾癌进展和治疗抵抗中扮演重要角色。因此，探索该疾病的潜在“免疫途径”是该领域的一项基本挑战。

发表在《癌细胞》杂志上的两项新研究中，达纳-法伯癌症研究所以及麻省理工学院-哈佛大学博德研究所的研究人员，使用了新兴的单细胞RNA测序技术来更清晰地了解肾脏肿瘤的微环境如何响应免疫疗法。研究人员认为，这项工作为新的药物疗法提供了潜在靶点。

达纳-法伯癌症研究所肿瘤学家、哈佛医学院医学副教授、布罗德研究所副研究员Eliezer Van Allen博士是本次研究中一篇论文的共同作者，他说：“我们有治疗肾癌患者的标准疗法，但许多患者对现有疗法没有反应。我们需要发现新的靶标。”

达纳-法伯干细胞移植和细胞疗法研究组负责人、哈佛医学院医学教授、布罗德研究所副研究员Catherine J. Wu也是研究论文的共同作者之一，他说：“这些努力为研究晚期肾脏肿瘤及其周围的生物微环境提供了重要的新思路。基于加深的理解，研究人员将能够确定新的潜在药物治疗靶标，并从总体上扩大能够接受有效治疗的患者人数。”

达纳-法伯癌症研究所兰克泌尿生殖肿瘤中心主任、布罗德研究所副研究员、哈佛医学院的杰罗姆和南希·科尔伯格医学教授Toni K. Choueiri博士也是两篇论文的共同作者，他补充道：“患者的免疫系统在控制癌症进展和响应免疫疗法中起着至关重要的作用。我们不太清楚为什么有些肿瘤会作出反应，而有些却没有。我们也不知道为什么肾癌会对免疫疗法产生抗药性。这两项研究是一个庞大团队的努力成果，旨在帮助我们从细胞水平和细胞RNA层面对肿瘤和免疫系统有更清晰的认知。”

使用免疫疗法时，通常会给患者提供免疫检查点封锁（ICB,通常与VEGF酪氨酸激酶抑制剂TKIs联用）。这些药物旨在避免免疫系统自动停止，使免疫系统像对待其它任何有害病原体一样攻击肿瘤。但是，免疫疗法仅在大约一半的肾透明细胞癌（ccRCC）患者中获得成功。并且，随着时间的推移，几乎所有患者都对治疗产生了抗药性。

根据美国癌症协会的数据，在美国，每年大约有76,000人被诊断出患有肾癌，13,000多人因肾癌死亡。

寻找新的靶点来破除免疫功能途径的障碍

在一项研究中，研究人员对来自肿瘤和邻近非肿瘤组织的164,722个单个细胞进行了单细胞RNA测序及T细胞受体测序。这些样本来自13位患有肾透明细胞癌（ccRCC）的患者，这些患者处于疾病的不同阶段（早期，局部晚期和晚期/转移性）。肾透明细胞癌患者占全部肾癌患者的80％。

在大多数实体瘤中，存在特定类型的免疫细胞CD8 + T细胞是一件好事。它们的存在表明免疫系统正在发挥作用。但是，研究人员发现，在晚期疾病中，这些CD8 + T细胞被“耗尽”，无法正常执行功能。

研究人员还发现，晚期疾病中存在更多的抗炎或“ 类M2”巨噬细胞，这是一种抑制免疫系统的白细胞。论文共同作者、达纳-法伯肿瘤学家、哈佛医学院医学讲师David A. Braun博士说，CD8+T细胞和巨噬细胞互相作用，并陷入“免疫功能障碍回路”。在晚期疾病样本中，巨噬细胞会产生促使CD8 + T细胞衰竭的分子。与此同时，那些CD8 + T细胞也会产生支持肿瘤前巨噬细胞生命的分子。

这些发现很重要，因为它们展现了潜在治疗靶标的全新面貌。Braun说：“我们已经靶向了肾癌的某些免疫系统途径，但是研究发现了许多其他导致细胞功能障碍的免疫抑制途径。随着研究的推进，我们可以研究所有这些相互作用，并找到新的机会来破坏这些途径，恢复免疫系统抗肿瘤作用，最终改善肾癌患者预后。”

识别PD-1 / PD-L1轴之外的治疗方法

今天发表的另一项研究着眼于ccRCC免疫疗法中的肿瘤和免疫重编程。

当前，针对ccRCC的大多数免疫疗法均以PD-1 / PD-L1轴为靶标，该途径产生能够阻止免疫系统攻击癌细胞的蛋白质。一旦阻止这一途径，免疫系统就会恢复功能、破坏癌细胞。

但是这些药物仅对一半的ccRCC患者有效，并且几乎所有患者最终都会对该药物产生耐药性。

达纳-法伯癌症研究所的计算生物学家，论文的共同主要作者Kevin Bi说：“在PD-1 / PD-L1之外可能还存在逃避免疫的机制，它们在药物响应或药物抵抗中起着重要作用。”

研究人员使用单细胞RNA测序技术，从8位患者的样本中提取了34326个细胞，其中7位患有转移性肾癌，而1位患有局部疾病。五份样本来自已经接受ICB或ICB+TKI组合治疗的患者。接受ICB治疗的患者均使用了专门针对PD-1 / PD-L1轴的药物。

研究人员发现，ICB通过以下几种方式重塑癌症微环境，并改变了癌症与免疫细胞的相互作用方式：

在肿瘤对治疗有响应的患者中，细胞毒性T细胞的一部分（即抗癌淋巴细胞）表达更高水平的共抑制受体和效应分子。

接受治疗患者的活检组织中，巨噬细胞会响应富含干扰素的微环境而转变为促炎状态，但免疫抑制标志物也会上调。

在接受ICB治疗的癌细胞中，研究人员发现了两个亚群，它们在血管生成信号和免疫抑制程序上调方面存在区别。

在接受ICB治疗的早期癌症中，癌细胞亚群和免疫逃避的表达特征与PBRM1突变有关，PBRM1突变是ccRCC中第二常见的基因突变。

Meng Xiao He是哈佛大学生物物理专业的研究生，达纳-法伯研究所范艾伦实验室的成员，并且是该论文的主要联合作者。他认为，这些发现表明了探索PD-1 / PD-L1轴之外的免疫途径的重要性。

他说：“我们需要研究的不仅仅是CD8 + T细胞。我们还应研究巨噬细胞，其他一些免疫检查点，并评估可能的新靶标。我们仍处于尝试了解不同疾病对免疫疗法抗药性机制的早期阶段。仍有许多尝试的余地，以使更多的人对治疗作出响应，并且让这些响应持续下去。”

英文原文

Research leads to better understanding of the immune system in kidney cancer

In the last two decades, immunotherapy has emerged as a leading treatment for advanced renal carcinoma cancer (more commonly known as kidney cancer). This therapy is now part of the standard of care, but it doesn't work for all patients, and almost all patients, no matter how they respond initially, become more resistant to treatment over time. The immune system plays a critical role in kidney cancer disease progression and in response to therapies, and so a fundamental challenge in the field is to understand the underlying "immune circuitry" of this disease.

In two new studies published today in Cancer Cell, researchers from Dana-Farber Cancer Institute and the Broad Institute of MIT and Harvard used the emerging technology of single-cell RNA sequencing to draw a clearer picture of how kidney tumors' microenvironments change in response to immunotherapy. The researchers believe that this work points to potential targets for new drug therapies.

"We have a standard of care for treating kidney cancer patients, but many patients do not respond to existing therapies, and we need to discover new targets," said Eliezer Van Allen, MD, an oncologist at Dana-Farber, associate professor of medicine at Harvard Medical School, associate member at the Broad Institute, and co-senior author on one of the papers.

"These companion studies shed important new light on the biology of advanced kidney tumors and their surrounding environments. With this increased understanding, researchers will be able to identify new potential drug treatment targets and, overall, expand the number of patients who can receive effective treatment," remarked Catherine J. Wu, MD, chief of the Division of Stem Cell Transplantation and Cellular Therapies at Dana-Farber, professor of medicine at Harvard Medical School, an institute member at the Broad, and co-senior author on one of the papers.

"A patient's immune system plays a critical role in controlling both the progression of cancer and the response to immune therapies," adds Toni K. Choueiri, MD director of the Lank Center for Genitourinary Oncology at Dana-Farber, an associate member at the Broad, and the Jerome and Nancy Kohlberg Professor of Medicine at Harvard Medical School. Choueiri is co-senior author on both papers. "We don't quite know why some tumors respond and some don't. We also don't know why kidney cancers become resistant to immunotherapy. These two studies are a large team effort to give us a sharper image of what happens on not just the cellular level but down to the RNA of each of those cells."

With immunotherapy, patients are typically given an immune checkpoint blockade (ICB) (often in combination with VEGF tyrosine kinase inhibitors; TKIs). The drugs are designed to stop the immune system from stopping itself, thus allowing it to attack the tumor like any other unwanted pathogen. However, immunotherapy is only successful in about half of ccRCC patients, and almost all patients build resistance to the treatment over time.

About 76,000 Americans are diagnosed with kidney cancer in the U.S. each year, which is also responsible for more than 13,000 deaths annually, according to the American Cancer Society.

Finding New Targets to Disrupt an Immune Dysfunction Circuit

In one study, researchers performed single-cell RNA and T cell receptor sequencing on 164,722 individual cells from tumor and adjacent non-tumor tissue. These samples came from 13 patients with clear cell renal cell carcinoma (ccRCC), which make up 80 percent of kidney cancer cases, at different stages of disease: early, locally advanced and advanced/metastatic.

In most solid tumors, the presence of a specific type of immune cell, the CD8+ T cell is a good thing. Their presence shows the immune system is working. However, researchers found that in advanced stage disease these CD8+ T cells were "exhausted," and not able to carry out their usual function.

They also discovered more anti-inflammatory or "M2-like" macrophages, a type of white blood cell that suppresses the immune system, in advanced stage disease. CD8+ T cells and macrophages were playing off each other and caught in an "immune dysfunction circuit," said co-lead author David A. Braun, MD, Ph.D., an oncologist at Dana-Farber and instructor of medicine at Harvard Medical School. In advanced disease samples, macrophages produce molecules that support CD8+ T cell exhaustion, at the same time those CD8+ T cells make molecules that supported the life of pro-tumor macrophages.

These findings are important because they "open up a whole new landscape of potential treatment targets," said Braun. "We already target some of the immune system pathways in kidney cancer, but our work uncovered many other immune inhibitory pathways supporting cell dysfunction. As we move forward, we can look at all of these interactions and identify new opportunities to disrupt the circuit, with the goal of restoring the immune system's anti-tumor effect and ultimately improving outcomes for patients with kidney cancer.

Identifying Treatments Beyond the PD-1/PD-L1 Axis

The other study published today looks at tumor and immune reprogramming during immunotherapy in ccRCC.

Most current immunotherapy treatments for ccRCC target the PD-1/PD-L1 axis, a pathway that makes proteins that halt the immune system from attacking cancer cells. Stop the stoppers, and the immune system can go after cancer cells.

But these drugs are only effective in half of ccRCC patients, and almost all patients eventually develop resistance to the drug.

"There may be immune evasion mechanisms outside of PD-1/PD-L1 that play an important role in response or resistance," said Kevin Bi, computational biologist at Dana-Farber and co-lead author on the paper.

Researchers used single-cell RNA sequencing to look 34,326 total cells drawn from samples from eight patients, seven of whom had metastatic renal cancer and one with localized disease. Five samples were from patients who had already received treatment, either through ICB, or a combination of ICB and TKI. Those treated with ICB were all given drugs that specifically targeted the PD-1/PD-L1 axis.

Researchers found that ICB remodels the cancer microenvironment and changes how cancer and immune cells interact, in a few ways:

In patients whose cancer responded to treatment, subsets of cytotoxic T-cells, which are cancer-fighting lymphocytes, express higher levels of co-inhibitory receptors and effector molecules.

Macrophages from treated biopsies shift towards pro-inflammatory states in response to an interferon-rich microenvironment but also upregulate immunosuppressive markers.

In cancer cells treated with ICB, researchers found two subpopulations, differing in angiogenic signaling and upregulation of immunosuppressive programs.

In advance stage cancers treated with ICB, expression signatures for cancer cell subpopulations and immune evasion were associated with the PBRM1 mutation, the second most commonly mutated gene in ccRCC.

These findings show the importance of exploring immune pathways away from the PD-1/PD-L1 axis, said Meng Xiao He, a graduate student in the Harvard Biophysics program, member of the Van Allen lab at Dana-Farber, and a co-lead author on the paper.

"We need to look at things that are not just CD8+ T cells. We should look at macrophages, some of the other immune checkpoints, and assess what may be targetable," he said. "We're still in the early days of trying to understand the mechanisms of immunotherapy resistance in different diseases. There's a lot of room to keep trying so that more people respond, and those responses hold.

参考文献：

"Progressive immune dysfunction with advancing disease stage in renal cell carcinomas" Cancer Cell (2021). 

本文内容由振东健康网整理发布