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* These authors contributed equally
The experimental design presented here provides a useful reproductive model for the studies of antigen-specific CD8+ T cells during lymph node (LN) metastasis, which excludes the perturbation of bystander CD8+ T cells.
Tumor antigen-specific CD8+ T cells from draining lymph nodes gain an accumulating importance in mounting anti-tumor immune response during tumorigenesis. However, in many cases, cancer cells form metastatic loci in lymph nodes before further metastasizing to distant organs. To what extent the local and systematic CD8+ T cell responses were influenced by LN metastasis remains obscure. To this end, we set up a murine LN metastasis model combined with a B16F10-GP melanoma cell line expressing the surrogate neoantigen derived from lymphocytic choriomeningitis virus (LCMV), glycoprotein (GP), and P14 transgenic mice harboring T cell receptors (TCRs) specific to GP-derived peptide GP33-41 presented by the class I major histocompatibility complex (MHC) molecule H-2Db. This protocol enables the study of antigen-specific CD8+ T cell responses during LN metastasis. In this protocol, C57BL/6J mice were subcutaneously implanted with B16F10-GP cells, followed by adoptive transfer with naive P14 cells. When the subcutaneous tumor grew to approximately 5 mm in diameter, the primary tumor was excised, and B16F10-GP cells were directly injected into the tumor draining lymph node (TdLN). Then, the dynamics of CD8+ T cells were monitored during the process of LN metastasis. Collectively, this model has provided an approach to precisely investigate the antigen-specific CD8+ T cell immune responses during LN metastasis.
Cancer immunotherapy, especially the immune checkpoint blockade (ICB), has revolutionized cancer therapy1. ICB blocks the coinhibitory immunoreceptors (such as PD-1, Tim-3, LAG-3, and TIGIT), which are highly expressed in exhausted CD8+ T cells in the tumor microenvironment (TME), leading to the reinvigoration of exhausted CD8+ T cells2. Considering the heterogeneity of exhausted CD8+ T cells, accumulating evidence revealed that tumor-specific CD8+ T cells derived from the periphery, including draining lymph node (dLN), but not in TME, mediate the efficacy of ICB3,4,5,6,7,8. Recently, TdLN derived TCF-1+TOX- tumor-specific memory CD8+ T cells (TdLN-TTSM) was confirmed to be the genuine responders to ICB which embody several functional properties of conventional memory T cells and could further expand and differentiate into progeny exhausted cells upon ICB treatment9. Altogether, these findings corroborated the importance of LN in mounting anti-tumor immunity.
Lymph node functions as a critical place in facilitating the priming and activation of tumor-specific CD8+ T cells by providing structural basis as well as biological signals10. Several types of cancer cells frequently seed sentinel lymph node (SLN, the first LN draining a primary tumor) before systematic dissemination11. The presence of SLN metastasis is linked with poor outcome in human cancer and preclinical models showed that tumor cells in TdLN could spread to distant organs through both the lymphatic vessels and blood vessels of the node12,13,14,15. SLN biopsy now represents a standard procedure to guide subsequent treatment decisions in many solid tumor types which could avoid unnecessary resection of uninvolved LN16,17. Even to the involved LN, it remains controversial whether and when surgical resection is needed as several studies have demonstrated that the removal of regional LN did not exhibit improved overall survival compared to those that received radiation or systemic therapy without regional LN resection18,19. One interpretation is that metastatic LN (mLN) with microscopic disease may retain some capacity to educate immune cells and provide some therapeutic benefits. So, it is critically important to elucidate how LN metastasis affects the anti-tumor immune response, especially the properties and functions of TdLN-TTSM.
Until now, both preclinical and clinical data have revealed some structural and cellular alterations in mLN20. However, the dynamic changes of tumor-specific CD8+ T cells during LN metastasis have not been delineated. Therefore, developing a compelling model of LN metastasis is needed for further investigation. Indeed, several studies have reported mLN mouse models through different ways14,21,22. For example, spontaneous metastasis in axillary LNs was conducted through the implantation of 4T1 breast cancer cells into the mammary fat pad22. In another study, Reticker-Flynn et al. generated melanoma cell lines with high incidence of spread from subcutaneous primary tumor to LNs through serial inoculation of tumor cells cultured from dissociated mLN tissues (nine rounds)14. Another commonly used model was prepared by the injection of tumor cells into the footpad and the metastatic loci would be formed in popliteal LN22. Notably, it is difficult to evaluate the precise timepoints of intervention because LN metastasis in these models is not always faithful.
In the present study, a murine LN metastatic model was established through the intranodal injection of B16F10-GP cells23,24, generated by CRISPR/Cas9-mediated insertion of LCMV virus glycoprotein (GP) gene sequence into the genome of B16F10 cell line9. Then, these mice were transferred with P14 cells which harbor transgenic T cell receptors (TCRs) specifically recognize the H-2Db GP33-41 epitope25,26 and the systemic and local dynamics of antigen-specific CD8+ T cells during LN metastasis could be investigated. Our experimental design provides a useful model for the study of immune responses, especially the antigen-specific CD8+ T cells during the LN metastasis which excludes the perturbation of bystander CD8+ T cells. These results would affect the clinical treatment options of whether to remove or retain the mLN and shed new light on the manipulation of mLN to achieve maximum therapeutic benefits.
The C57BL/6J mice (referred to B6 mice) and naive P14 transgenic mice9,27 used were 6-10 weeks of age weighing 18-22 g. Both male and female were included without randomization or blinding. All animal studies were conducted in accordance with the guidelines of the Institutional Animal Care and Use Committee of the Qingdao Agricultural University.
1. Preparation of medium and reagents
2. Preparation of B16F10-GP cell suspension
3. Ectopic inoculation of B16F10-GP cells in the bilateral inguinal region of mice
4. Adoptive transfer of P14 T cells into tumor-bearing mice
5. Resection of the primary tumor
NOTE: Ensure all surgical instruments are autoclaved before use. Sterilize the operating area inside the biosafety cabinet with 75% ethanol, followed by UV irradiation for at least 30 min. Wear clean gowns, hats, masks, and sterile gloves during surgery.
6. Intranodal injection of B16F10-GP cells in the inguinal lymph node
NOTE: After bilateral tumor clearance, B16F10-GP cells were injected into unilateral inguinal lymph node and PBS was injected into the other side.
The schematic diagram of this experimental design is shown in Figure 1A. A total of 5 x 105 B16F10-GP cells in 100 µL of PBS were subcutaneously (s.c.) implanted into the bilateral inguinal region of CD45.2 C57BL/6J mice. After 7 days, these tumor-bearing mice were intraperitoneally (i.p.) injected with 4 mg CTX, followed by the adoptive transfer of 5 x 105 CD45.1+P14 cells through tail intravenous (i.v.) injection. When tumors grew to approximately 3-5 ...
During tumorigenesis, antigen-presenting cells (APCs) engulf tumor antigens and migrate to TdLN where they prime CD8+ T cells. After priming and activation, CD8+ T cells leave the TdLN and infiltrate the tumor to kill tumor cells10. Through TdLN resection and the administration of FTY720 which block the exit of immune cells from the lymphoid organs, several studies have demonstrated the pivotal role of TdLN in ensuring the efficacy of PD-1/PD-L1 checkpoint therapy
The authors declare no competing interests.
This work was supported by the National Science Foundation for Outstanding Young Scholars of China (No. 82122028 to LX), the National Natural Science Foundation of China (No. 82173094 to LX), Natural Science Foundation of Chong Qing (No. 2023NSCQ-BHX0087 to SW).
Name | Company | Catalog Number | Comments |
1.5 mL centrifuge tube | KIRGEN | KG2211 | |
100 U insulin syringe | BD Biosciences | 320310 | |
15 mL conical tube | BEAVER | 43008 | |
2,2,2-Tribromoethanol (Avertin) | Sigma | T48402-25G | |
2-Methyl-2-butanol | Sigma | 240486-100ML | |
70 μm nylon cell strainer | BD Falcon | 352350 | |
APC anti-mouse CD45.1 | BioLegend | 110714 | Clone:A20 |
B16-GP cell line | Beijing Biocytogen Co.Ltd, China | Custom | |
BSA-V (bovine serum albumin) | Bioss | bs-0292P | |
cell culture dish | BEAVER | 43701/43702/43703 | |
centrifuge | Eppendorf | 5810R-A462/5424R | |
cyclophosphamide | Sigma | C0768-25G | |
Cyclophosphamide (CTX) | Sigma | PHR1404 | |
Dulbecco's Modified Eagle Medium | Gibco | C11995500BT | |
EDTA | Sigma | EDS-500g | |
FACS tubes | BD Falcon | 352052 | |
fetal bovine serum | Gibco | 10270-106 | |
flow cytometer | BD | FACSCanto II | |
hemocytometer | PorLab Scientific | HM330 | |
isoflurane | RWD life science | R510-22-16 | |
KHCO3 | Sangon Biotech | A501195-0500 | |
LIVE/DEAD Fixable Near-IR Dead Cell Stain Kit, for 633 or 635 nm excitation | Life Technologies | L10199 | |
needle carrier | RWD Life Science | F31034-14 | |
NH4Cl | Sangon Biotech | A501569-0500 | |
paraformaldehyde | Beyotime | P0099-500ml | |
PE anti-mouse TCR Vα2 | BioLegend | 127808 | Clone:B20.1 |
Pen Strep Glutamine (100x) | Gibco | 10378-016 | |
PerCP/Cy5.5 anti-mouse CD8a | BioLegend | 100734 | Clone:53-6.7 |
RPMI-1640 | Sigma | R8758-500ML | |
sodium azide | Sigma | S2002 | |
surgical forceps | RWD Life Science | F12005-10 | |
surgical scissors | RWD Life Science | S12003-09 | |
suture thread | RWD Life Science | F34004-30 | |
trypsin-EDTA | Sigma | T4049-100ml |
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