Tumor-infiltrating lymphocytes (TILs) are a subtype of immune cells that infiltrate and accumulate within tumors. Studies proved that TILs can be used as prognostic and predictive markers for cancer patients\' responses to immunotherapy. This review explores the modern knowledge of TILs, the challenges and opportunities for utilizing TILs in cancer treatment, such as the rise of therapies under TIL circumstances, the identification of biomarkers for TIL activity, and methods used to isolate and expand TILs for therapeutic use. Ongoing clinical trials and promising results in different cancer types are highlighted, including melanoma, ovarian, and colorectal cancer. This also focuses on ongoing efforts to improve TIL-based therapies by identifying the specific subsets of TILs that are most effective in treating cancer and developing methods to increase the functionality and persistence of TILs in the tumor microenvironment. The article recapitulates the present state TILs therapy, ongoing research, and improvements to its potency.

Immunotherapies, mainly immune checkpoint inhibitors (ICIs), have revolutionized cancer treatment strategies over the past decade, but their limitations have limited clinical applications. Tumor-infiltrating lymphocyte (TIL) therapy is a type of adoptive cell therapy (ACT), which collects infiltrating lymphocytes at the tumor site and expands them in vitro to obtain TIL final products cloned by various T-cell receptors, subsequently reinfused TIL into the patient, which is effective for the treatment of solid tumors. The approval of Lifileucel for commercialization marks the success of TIL therapy. This review summarizes the current status of clinical trials of TIL treatment. In addition, it is suggested that the current research trend of TIL should focus on improving the survival time of TIL in vivo, reducing drug toxicity, and searching for prognostic markers. Finally, it is expected that TIL therapy can be applied to a more wide range of clinical treatments.

BACKGROUND: The association between tumor-infiltrating lymphocyte (TIL) levels and the response to neoadjuvant therapy (NAT) in patients with triple-negative breast cancer (TNBC) remains unclear.
OBJECTIVE: To investigate the predictive potential of TIL levels for the response to NAT in TNBC patients.
METHODS: A systematic search of the National Center for Biotechnology Information PubMed database was performed to collect relevant published literature prior to August 31, 2023. The correlation between TIL levels and the NAT pathologic complete response (pCR) in TNBC patients was assessed using a systematic review and meta-analysis. Subgroup analysis, sensitivity analysis, and publication bias analysis were also conducted.
RESULTS: A total of 32 studies were included in this meta-analysis. The overall meta-analysis results indicated that the pCR rate after NAT treatment in TNBC patients in the high TIL subgroup was significantly greater than that in patients in the low TIL subgroup (48.0% vs 27.7%) (risk ratio 2.01; 95% confidence interval 1.77-2.29; P < 0.001, I 2 = 56%). Subgroup analysis revealed that the between-study heterogeneity originated from differences in study design, TIL level cutoffs, and study populations. Publication bias could have existed in the included studies. The meta-analysis based on different NAT protocols revealed that all TNBC patients with high levels of TILs had a greater rate of pCR after NAT treatment in all protocols (all P ≤ 0.01), and there was no significant between-protocol difference in the statistics among the different NAT protocols (P = 0.29). Additionally, sensitivity analysis demonstrated that the overall results of the meta-analysis remained consistent when the included studies were individually excluded.
CONCLUSIONS: TILs can serve as a predictor of the response to NAT treatment in TNBC patients. TNBC patients with high levels of TILs exhibit a greater NAT pCR rate than those with low levels of TILs, and this predictive capability is consistent across different NAT regimens.

OBJECTIVE: Spontaneously occurring glioma in pet dogs is increasingly recognized as a valuable translational model for human glioblastoma. Canine high-grade glioma and human glioblastomas share many molecular similarities, including the accumulation of immunosuppressive regulatory T cells (Tregs) that inhibit anti-tumor immune responses. Identifying in dog mechanisms responsible for Treg recruitment may afford to target the cellular population driving immunosuppression, the results providing a rationale for translational clinical studies in human patients. Our group has previously identified C-C motif chemokine 2 (CCL2) as a glioma-derived T-reg chemoattractant acting on chemokine receptor 4 (CCR4) in a murine orthotopic glioma model. Recently, we demonstrated a robust increase of CCL2 in the brain tissue of canine patients bearing high-grade glioma.
METHODS: We performed a series of in vitro experiments using canine Tregs and patient-derived canine glioma cell lines (GSC 1110, GSC 0514, J3T-Bg, G06A) to interrogate the CCL2-CCR4 signaling axis in the canine.
RESULTS: We established a flow cytometry gating strategy for identifying and isolating FOXP3+ Tregs in dogs. The canine CD4 + CD25high T-cell population was highly enriched in FOXP3 and CCR4 expression, indicating they are bona fide Tregs. Canine Treg migration was enhanced by CCL2 or by glioma cell line-derived supernatant. Blockade of the CCL2-CCR4 axis significantly reduced migration of canine Tregs. CCL2 mRNA was expressed in all glioma cell lines, and expression increased when exposed to Tregs but not CD4 + helper T-cells.
CONCLUSIONS: Our study validates CCL2-CCR4 as a bi-directional Treg-glioma immunosuppressive and tumor-promoting axis in canine high-grade glioma.

UNASSIGNED: Spontaneously occurring glioma in pet dogs is increasingly recognized as a valuable translational model for human glioblastoma. Canine high grade glioma and human glioblastomas share many molecular similarities, including accumulation of immunosuppressive regulatory T cells (Tregs) that inhibit anti-tumor immune responses. Identifying in dog mechanisms responsible for Treg recruitment may afford targeting the cellular population driving immunosuppression, the results providing a rationale for translational clinical studies in human patients. Our group has previously identified C-C motif chemokine 2 (CCL2) as a glioma-derived T-reg chemoattractant acting on chemokine receptor 4 (CCR4) in a murine orthotopic model of glioma. Recently, we demonstrated a robust increase of CCL2 in the brain tissue of canine patients bearing high-grade glioma.
UNASSIGNED: We performed a series of in vitro experiments using canine Tregs and patient-derived canine glioma cell lines (GSC 1110, GSC 0514, J3T-Bg, G06A) to interrogate the CCL2-CCR4 signaling axis in the canine.
UNASSIGNED: We established a flow cytometry gating strategy for identification and isolation of FOXP3+ Tregs in dogs. The canine CD4 + CD25high T-cell population was highly enriched in FOXP3 and CCR4 expression, indicating they are bona fide Tregs. Canine Treg migration was enhanced by CCL2 or by glioma cell line-derived supernatant. Blockade of the CCL2-CCR4 axis significantly reduced migration of canine Tregs. CCL2 mRNA was expressed in all glioma cell lines and expression increased when exposed to Tregs but not to CD4 + helper T-cells.
UNASSIGNED: Our study validates CCL2-CCR4 as a bi-directional Treg-glioma immunosuppressive and tumor-promoting axis in canine high-grade glioma.

UNASSIGNED: Aurora kinase A (AURKA) and tumor-infiltrating lymphocytes (TILs) are both known to play an essential role in tumorigenesis. However, the expression and prognostic value of the AURKA and TILs in medullary thyroid carcinoma (MTC) have not yet been investigated.
UNASSIGNED: Surgical specimens and clinical data of 137 patients diagnosed with MTC were collected. AURKA expression and TILs infiltration were quantified by immunohistochemistry and hematoxylin-eosin staining. Subsequently, the prognostic value of AURKA expression and TIL infiltration in MTC was evaluated.
UNASSIGNED: AURKA was highly expressed in patients with multifocal tumor, cervical lymph node metastasis, and an advanced TNM stage, indicating a high probability of recurrence. AURKA further exhibited a positive correlation with TILs (R = 0.44, P < 0.001). High expression of AURKA combined with a low numbers of TILs (AURKAhigh/TILslow) was identified as an independent prognostic factor for biochemical recurrence (odds ratio: 4.57, 95% confidence interval: 1.54-14.66, P < 0.01) and recurrence-free survival (hazard ratio: 3.64, 95% confidence interval: 1.52-8.71, P < 0.001). The combination of AURKA and TILs apparently improves the prognostic value for biochemical recurrence (area under the curve: 0.751) and structural recurrence (area under the curve: 0.836) of MTC. Notably, AURKAhigh/TILslow demonstrated a high value for prediction of distant or unresectable locoregional recurrence, with an overall accuracy of 86.9%.
UNASSIGNED: AURKAhigh is associated with the MTC malignancy. The combination of AURKAhigh/TILslow was identified as novel independent prognostic marker in MTC, predicting incurable disease recurrence with high accuracy.

OBJECTIVE: We aimed to explore the effects and mechanisms of action of dehydroepiandrosterone (DHEA) on immune evasion of oral squamous cell carcinoma (OSCC) to provide evidence for enhancing the effect of immunotherapy.
METHODS: A xenograft mouse model and immunohistochemistry were used to reveal the patterns of tumor-infiltrating lymphocytes (TILs). The CAL27 and SCC VII cell lines were used for the in vitro study. Western blotting, qPCR, immunofluorescence, and flow cytometry were used to evaluate the expression of B7-H4. Recombinant mouse B7-H4 protein (rmB7-H4) and PG490, an inhibitor of NF-κB p65 were used for the \"rescue study.\" Gain- and loss-of-function, luciferase reporter, and chromatin immunoprecipitation assays were performed to verify this mechanism.
RESULTS: DHEA inhibited tumor growth in an OSCC xenograft mouse model, increased CD8 + cells, and decreased FOXP3 + cells in TILs. DHEA reduced the expression of B7-H4 in CAL27 and SCC VII cells RmB7-H4 reverses the effect of DHEA on tumor growth and TIL patterns. DHEA increased the expression of miR-15b-5p and activated its transcriptional factor NF-κB p65. Further experiments demonstrated that miR-15b-5p inhibited B7-H4 expression by binding to its 3\'-UTR regions, and NF-κB p65 activated miR-15b transcription. PG490 reversed the effects of DHEA on tumor growth, antitumor immunity in the OSCC xenograft model, and the expression/phosphorylation of NF-κB p65, miR-15b-5p, and B7-H4.
CONCLUSIONS: This study indicates that DHEA attenuates the immune escape of OSCC cells by inhibiting B7-H4 expression, providing new insights for cancer immunotherapy.

Prostaglandin E2 (PGE2) is well known to promote tumor progression by boosting cancer cell proliferation while inhibiting anticancer immunity. Recent data from Lacher et al. and Morotti et al. demonstrate that one of the mechanisms through which PGE2 suppresses tumor-targeting immune responses involves downregulation of interleukin 2 (IL2) receptors and consequent inhibition of mitochondrial metabolism in T cells.

BACKGROUND: Tumor-infiltrating lymphocyte (TIL) therapy has been restricted by intensive lymphodepletion and high-dose intravenous interleukin-2 (IL-2) administration. To address these limitations, we conducted preclinical and clinical studies to evaluate the safety, antitumor activity, and pharmacokinetics of an innovative modified regimen in patients with advanced gynecologic cancer.
METHODS: Patient-derived xenografts (PDX) were established from a local recurrent cervical cancer patient. TILs were expanded ex vivo from minced tumors without feeder cells in the modified TIL therapy regimen. Patients underwent low-dose cyclophosphamide lymphodepletion followed by TIL infusion without intravenous IL-2. The primary endpoint was safety; the secondary endpoints included objective response rate, duration of response, and T cell persistence.
RESULTS: In matched patient-derived xenografts (PDX) models, homologous TILs efficiently reduced tumor size (p < 0.0001) and underwent IL-2 absence in vivo. In the clinical section, all enrolled patients received TIL infusion using a modified TIL therapy regimen successfully with a manageable safety profile. Five (36%, 95% CI 16.3-61.2) out of 14 evaluable patients experienced objective responses, and three complete responses were ongoing at 19.5, 15.4, and 5.2 months, respectively. Responders had longer overall survival (OS) than non-responders (p = 0.036). Infused TILs showed continuous proliferation and long-term persistence in all patients and showed greater proliferation in responders which was indicated by the Morisita overlap index (MOI) of TCR clonotypes between infused TILs and peripheral T cells on day 14 (p = 0.004) and day 30 (p = 0.004). Higher alteration of the CD8+/CD4+ ratio on day 14 indicated a longer OS (p = 0.010).
CONCLUSIONS: Our modified TIL therapy regimen demonstrated manageable safety, and TILs could survive and proliferate without IL-2 intravenous administration, showing potent efficacy in patients with advanced gynecologic cancer.
BACKGROUND: NCT04766320, Jan 04, 2021.

BACKGROUND: Adoptive transfer of in vitro expanded tumor-infiltrating lymphocytes (TILs) has been effective in regressing several types of malignant tumors. This study assessed the yield and factors influencing the successful expansion of tumor-infiltrating lymphocytes (TILs) from head and neck squamous cell carcinoma (HNSCC), along with their immune phenotypes.
METHODS: TILs were expanded from 47 surgically resected HNSCC specimens and their metastasized lymph nodes. The cancer tissues were cut into small pieces (1-2 mm) and underwent initial expansion for 2 weeks. Tumor location, smoking history, stromal TIL percentage, human papillomavirus infection, and programmed death-ligand 1 score were examined for their impact on successful expansion of TILs. Expanded TILs were evaluated by flow cytometry using fluorescence-activated cell sorting. A second round of TIL expansion following the rapid expansion protocol was performed on a subset of samples with successful TIL expansion.
RESULTS: TILs were successfully expanded from 36.2% samples. Failure was due to contamination (27.6%) or insufficient expansion (36.2%). Only the stromal TIL percentage was significantly associated with successful TIL expansion (p = 0.032). The stromal TIL percentage also displayed a correlation with the expanded TILs per fragment (r = 0.341, p = 0.048). On flow cytometry analysis using 13 samples with successful TIL expansion, CD4 + T cell dominancy was seen in 69.2% of cases. Effector memory T cells were the major phenotype of expanded CD4 + and CD8 + T cells in all cases.
CONCLUSIONS: We could expand TILs from approximately one-third of HNSCC samples. TIL expansion could be applicable in HNSCC samples with diverse clinicopathological characteristics.