Anti-tumor effects of anti-PD-1 antibody, pembrolizumab, in humanized NSG PDX mice xenografted with dedifferentiated liposarcoma
Introduction
Soft tissue sarcoma (STS) represents a heterogeneous group of rare malignant tumors that account for less than 1% of human malignancies [1,2]. Clinically, approximately 50% of resected STSs produce a recurrence [[1], [2], [3]], and to date, 50 different types of soft tissue sarcoma have been reported [4,5]. Among these, liposarcoma, which is known to occur in soft tissue with adipocytes such as the inner thighs and retroperitoneum [6], are prominent tumors in pediatric sarcoma patients (accounting for 10%) and adolescent and adult sarcoma patients (accounting for 8%) [7]. Malignant adipocytic neoplasms consist of three distinct clinicopathological entities: well‐differentiated/dedifferentiated liposarcoma (WDDLPS/DDLPS), myxoid liposarcoma, and pleomorphic liposarcoma (PLPS). Until recently, liposarcoma management had involved surgical removal of the tumor and margin [8] as primary treatment, but incomplete resection may result in recurrence or metastatic disease that can ultimately lead to malignant tumors [8,9]. Although radiation and chemotherapy are considered useful adjunct treatments for patients with malignant liposarcoma [10], no specific regimen has been developed so far. For this reason, immunotherapy is currently being considered as a novel therapeutic approach.
Various types of immunotherapy have been proposed and developed in recent years [11,12], and promising agents that target immune regulatory checkpoints, such as cytotoxic T-lymphocyte antigen-4 (CTLA-4) and programmed cell death protein-1 (PD-1)/PD-L1, have generated attention [[11], [12], [13]]. Thus far, numerous scientific and clinical studies have shown that the blockade of immune checkpoints is a successful strategy to treat several types of malignant tumors, with increased survival times in tandem with tumor regression [[11], [12], [13], [14], [15]]. Consequently, the monoclonal antibody (mAb) blockade of CTLA4 or PD-1/PD-L1 has been approved by the FDA for use as first- or second-line therapy [[16], [17], [18], [19]]. Multiple trials have demonstrated that PD-1 blockade exhibits effective anti-tumor activity in different malignancies, including bladder cancer, breast cancer, colorectal cancer, renal cell carcinoma, small cell lung cancer and uterine cancer [15,[20], [21], [22], [23]]. However, such blockade has never been attempted for liposarcoma.
The administration of mAbs blocking PD-1/PD-L1 allows the generation of a sustained and specific CTL response capable of tumor cell lysis [15]. From an immunological point of view, anti-PD-1 therapy is critically dependent on having sufficient numbers of PD-1 positive immune cells, such as PD-1+CD8+ T and PD-1+ NK cells, capable of exerting anti-cancer effects [15,[24], [25], [26]]. A recent study demonstrated that the abundance of CD8+ T-cell was the most predictive parameter of the response to anti-PD-1/PD-L1 therapy across various cancer types, followed by the tumor mutational burden and the fraction of samples with high PD1 gene expression [27]. In addition, a recent report has shown that improvements of survival and responsible rate to PD1 blockade with pembrolizumab in a phase 2 clinical trial of STS patients were favorably associated with CD8+ T cell signature and PD1, along with high infiltration of B cells [28]. Importantly, 58% of soft tissue sarcomas had intratumoral infiltration of PD-1-positive lymphocytes, and 65% of soft tissue sarcomas expressed PD-L1 [29], strongly suggesting a potential tumor target for anti-PD-1 therapy in the future.
Our pan-cancer analysis of The Cancer Genome Atlas (TCGA) data suggests that liposarcoma is a possible tumor target for anti-PD-1 therapy, and we therefore investigate anti-PD-1 effects in NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice xenografted with DDLPS. Our results demonstrate that the anti-PD-1 effects on DDLPS tumors were markedly associated with an abundance of hCD8+ T subsets, such as hCD8+IFNγ+, hCD8+PD-1+, and hCD8+Ki-67+ cells, and hNK subsets, such as hCD56+IFNγ+, hCD56+PD-1+, hCD56+Ki-67+ cells, in humanized NSG PDX mice treated with the anti-PD-1 antibody pembrolizumab. Importantly, the survival of sarcoma patients was positively associated with high levels of immune-related factors, such as IL2 signature, CD8 abundance, NK active abundance, IFNγ signature, and cytolytic score, supporting that hCD8 and hNK cells might play a role of anti-DDLPS effects in anti-PD-1 therapy. In summary, we provide in this study strong proof of principle supporting anti-PD-1 therapy targeting sarcomas including DDLPS, based on the functional abundance of hCD8+ and hNK cells in the tumor microenvironment.
Section snippets
Patients
Sarcoma patients were recruited at the Samsung Medical Center (SMC), and samples were collected as part of the Sarcoma study at SMC, Seoul, Korea (IRB: 2013-07-122). Anonymized sarcoma tumor tissues were collected with informed consent from patient 15 GS-002 (female, 60 years of age, retroperitoneum) while undergoing surgery or diagnostic core biopsy, according to the procedures approved by the Internal Review Board (IRB) of the SMC. Primary surgical and core biopsy sarcoma tumor tissues were
Association of immune factors, hCD8+ T and hCD56+ NK abundances, in patient-derived DDLPS tumors
Various immune cells prevalent in the tumor microenvironment are critically implicated in either tumor progression or regression [38,39] and play important roles in the context of cancer immunotherapy. To determine the cancer type that is most relevant to immune checkpoint therapy, we performed a pancancer analysis of TCGA RNAseq data of 21 tumor types. Our analysis on the association between the key immune-related factors (hereafter referred as IFs) and the survival of tumor patients suggests
Discussion
To date, many promising scientific and clinical reports have provided evidence of the efficacy and have defined the mechanisms of anti-PD-1 therapy for various types of cancer [[15], [16], [17], [18], [19], [20], [21], [22], [23]]. Nonetheless, such an approach has not yet been attempted for several other types of cancer, including sarcoma. Given previous reports that 58% of soft tissue sarcomas had intratumoral infiltration of PD-1-positive lymphocytes and 65% expressed PD-L1 [29], anti-PD-1
Funding
This work was supported by a grant of the National Research Foundation of Korea (NRF), funded by the Korean Government (NRF-2018R1D1A1B07042470 and NRF-2018M3A9H2021665) and the Korean Government(MSIP) (2016R1A5A2945889).
Declaration of competing interest
The authors declare no potential conflicts of interest.
Acknowledgment
We would like to thank Hyehwa Forum members for their helpful discussion.
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