Immunoscore system combining CD8 and PD-1/PD-L1: A novel approach that predicts the clinical outcomes for cervical cancer

Tissue contexture determines the pattern and density of tumor-infiltrating immune cells in HPV-associated squamous cell carcinomas of oropharynx and uterine cervix

The profile of the antitumor immune response is an important factor determining patient clinical outcome. However, the influence of the tissue contexture on the composition of the tumor microenvironments of virally induced tumors is not clearly understood. Therefore, we analyzed the immune landscape of two HPV-associated malignancies: oropharyngeal squamous cell carcinoma (OPSCC) and squamous cell carcinoma of uterine cervix (CESC). We employed multiplex immunohistochemistry and immunofluorescence to evaluate the density and spatial distribution of immune cells in retrospective cohorts of OPSCC and CESC patients. This approach was complemented by transcriptomic analysis of purified primary tumor cells and in silico analysis of publicly available RNA sequencing data. Transcriptomic analysis showed similar immune profiles in OPSCC and CESC samples. Interestingly, immunostaining of OPSCC tissues revealed high densities of immune cells in both tumor stroma and tumor epithelium, whereas CESC samples were mainly characterized by the lack of immune cells in the tumor epithelium. However, in contrast to other immune cell populations, polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) were abundant in both segments of CESC samples and CESC-derived tumor cells expressed markedly higher levels of the PMN-MDSC chemoattractants CXCL1, CXCL5, and CXCL6 than OPSCC tumor cells. Taken together, despite their having the same etiologic agent, the immune infiltration pattern significantly differs between OPSCC and CESC, with a noticeable shift toward prominent MDSC infiltration in the latter. Our data thus present a rationale for a diverse approach to targeted therapy in patients with HPV-associated tumors of different tissue origins.

Manipulating TGF-β signaling to optimize immunotherapy for cervical cancer

Cervical cancer is a serious threat to women's health globally. Therefore, identifying key molecules associated with cervical cancer progression is essential for drug development, disease monitoring, and precision therapy. Recently, TGF-β (transforming growth factor-beta) has been identified as a promising target for cervical cancer treatment. For advanced cervical cancer, TGF-β participates in tumor development by improving metastasis, stemness, drug resistance, and immune evasion. Accumulating evidence demonstrates that TGF-β blockade effectively improves the therapeutic effects, especially immunotherapy. Currently, agents targeting TGF-β and immune checkpoints such as PD-L1 have been developed and tested in clinical studies. These bispecific antibodies might have the potential as therapeutic agents for cervical cancer treatment in the future.

Association between Tumor Mutational Burden, Stromal CD8+ Tumor-Infiltrating Lymphocytes, and Clinical Factors in Cervical Cancers Treated with Radiotherapy

BACKGROUND

Tumor mutational burden (TMB) and stromal CD8-positive tumor-infiltrating lymphocytes (CD8⁺TILs) serve important roles in antitumor immune responses to radiotherapy. This study aimed to elucidate the association between TMB, CD8⁺TILs, and clinical factors in patients with cervical cancer treated with radiotherapy.

METHODS

Patients with squamous cell carcinoma of the uterine cervix treated with definitive radiotherapy, and with available somatic mutation data and immunohistochemical staining data from identical tumor tissues, were enrolled retrospectively. The association between TMB and/or CD8⁺TIL density and patient characteristics, mutation profiles, and treatment outcome was analyzed.

RESULTS

The study analyzed 44 patients (median follow-up period, 61 months). There was no significant correlation between TMB and CD8⁺TIL density, or between TMB or CD8⁺TIL density and patient characteristics. TMB-high or CD8⁺TIL density-low status was associated with worse overall survival and distant metastasis-free survival; the predictive value of these factors became greater when used in combination. TMB-high or CD8⁺TIL density-high status was associated with ARID1A mutations.

CONCLUSIONS

These data indicate independence of TMB and CD8⁺TIL density and the involvement of ARID1A alterations in antitumor immune responses in patients with cervical cancers treated with radiotherapy, warranting further mechanistic research and prospective validation.

Efficacy and Synergy with Cisplatin of an Adenovirus Vectored Therapeutic E1E2E6E7 Vaccine against HPV Genome-Positive C3 Cancers in Mice

Human papillomavirus (HPV) infections are the main cause of cervical and oropharyngeal cancers. As prophylactic vaccines have no curative effect, an efficient therapy would be highly desired. Most therapeutic vaccine candidates target only a small subset of HPV regulatory proteins, namely, E6 and E7, and are therefore restricted in the breadth of their immune response. However, research has suggested E1 and E2 as promising targets to fight HPV+ cancer. Here, we report the design of adenoviral vectors efficiently expressing HPV16 E1 and E2 in addition to transformation-deficient E6 and E7. Vaccination elicited vigorous CD4+ and CD8+ T-cell responses against all encoded HPV16 proteins in outbred mice and against E1 and E7 in C57BL/6 mice. Therapeutic vaccination of C3 tumor-bearing mice led to significantly reduced tumor growth and enhanced survival for both small and established tumors. Tumor biopsies revealed increased numbers of tumor-infiltrating CD8+ T cells in treated mice. Cisplatin enhanced the effect of therapeutic vaccination, accompanied by enhanced infiltration of dendritic cells into the tumor. CD8+ T cells were identified as effector cells in T-cell depletion assays, seemingly under regulation by FoxP3+CD4+ regulatory T cells. Finally, therapeutic vaccination with Ad-Ii-E1E2E6E7 exhibited significantly enhanced survival compared with vaccination with two peptides each harboring a known E6/E7 epitope. We hypothesize that this difference could be due to the induction of additional T-cell responses against E1. These results support the use of this novel vaccine candidate targeting an extended set of antigens (Ad-Ii-E1E2E6E7), in combination with cisplatin, as an advanced strategy to combat HPV+ cancers.

Immunoscore Combining CD8, FoxP3, and CD68-Positive Cells Density and Distribution Predicts the Prognosis of Head and Neck Cancer Patients

We assessed immune cell infiltrates to develop an immunoscore for prognosis and to investigate its correlation with the clinical data of patients with head and neck cancer. CD8, FoxP3, and CD68 markers were evaluated by immunohistochemistry in 258 carcinoma samples and positive cells were counted in stromal and intra-tumoral compartments. The RStudio software was used to assess optimal cut-offs to divide the population according to survival while the prognostic value was established by using Kaplan–Meier curves and Cox regression models for each immune marker alone and in combination. We found with univariate analysis that the infiltration of immune cells in both compartments was predictive for recurrence-free survival and overall survival. Multivariate analysis revealed that CD8+ density was an independent prognostic marker. Additionally, the combination of CD8, FoxP3, and CD68 in an immunoscore provided a significant association with overall survival (p = 0.002, HR = 9.87). Such an immunoscore stayed significant (p = 0.018, HR = 11.17) in a multivariate analysis in comparison to tumor stage and histological grade, which had lower prognostic values. Altogether, our analysis indicated that CD8, FoxP3, and CD68 immunoscore was a strong, independent, and significant prognostic marker that could be introduced into the landscape of current tools to improve the clinical management of head and neck cancer patients.

Programme death ligand 1 expressions as a surrogate for determining immunotherapy in cervical carcinoma patients

BACKGROUND

The programme death ligand1 and its receptor (PD-1/PD-L1) interaction is a target for blockage by immunotherapy that uses the body's own immune system. Some studies show that PD-L1 expressing tumours are also more aggressive with poor prognosis. This study evaluated the immunohistochemical expression of PD-L1 in uterine cervical carcinomas. Women with cervical cancer would benefit from its use as a marker in therapy and prognosis.

METHODS

Hospital-based cross-sectional retrospective study was conducted. The study materials included 183 archived formalin fixed and paraffin embedded (FFPE) tissue blocks with histological diagnosis of cervical carcinoma diagnosed in our facility within a five-year period (January 2012 and December 2016) that met the study criteria. Data were extracted from records in the Department and immunohistochemistry was done using polyclonal antibodies to PD-L1 (GTX104763, Genetex). Obtained data were analysed using SPSS version 23. P < 0.05 was considered significant.

RESULTS

A hundred and eighty-three cases of cervical cancer were studied. PD-L1 was positive in 57.4% of all cases. The diffuse pattern of staining was the major pattern accounting for 88.5% of positive cases. Poorly differentiated cervical carcinomas are less likely to express PD-L1. Within the histologic types, the squamous cell carcinomas expressed PD-L1 in 58.7%, and 50% of adenocarcinomas were positive. PD-L1 was not expressed in all cases of adenoid cystic carcinomas and basaloid squamous cell carcinomas.

CONCLUSION

A significant population of cervical carcinoma expresses PD-L1 by immunohistochemistry. PD-L1 prevalence is lower amongst the poorly differentiated cancers compared to other grades.

Radiotherapy for HPV-related cancers: prediction of therapeutic effects based on the mechanism of tumor immunity and the application of immunoradiotherapy

Human papillomavirus (HPV)-related cancer is one of the diseases entities for which the applications of radiotherapy have been increasing. Recently, the process of carcinogenesis from HPV infection and the mechanism of tumor immunity that develops during disease progression have been elucidated. In this review, we will describe the mechanism of tumor immunity and how chemoradiotherapy may overcome and improve the efficacy of tumor immunity. We will also discuss the usefulness of proteins involved with tumor immunity as a predictive marker of radiotherapy response, and present an overview of ongoing clinical trials of combinations of immune checkpoint inhibitors and radiotherapy to demonstrate the promising combination therapy that has been currently emerging.

Prognostic and therapeutic TILs of cervical cancer-Current advances and future perspectives

Cervical cancer is a top lethal cancer for women worldwide. Although screening and vaccination programs are available in many countries, resulting in the decline of new cases, this is not true for developing countries where there are many new cases and related deaths. Cancer immunotherapy through adaptive cell therapy (ACT) has been applied in clinics, but now much attention is focused on autogenic tumor-infiltrating lymphocyte (TIL)-based therapy, which has shown more specificity and better ability to inhibit tumor growth. Data from melanoma and cervical cancers confirm that tumor-specific T cells in TILs can be expanded for more specific and effective ACT. Moreover, TILs are derived from individual patients and are ready to home back to kill tumor cells after patient infusion, aligning well with personalized and precision medicine. In addition to therapy, TIL cell types and numbers are good indicators of host immune response to the tumor, and thus they have significant values in prognosis. Because of the special relationship with human papillomavirus (HPV) infection, cervical cancer has some specialties in TIL-based prognosis and therapy. In this review, we summarize the recent advances in the prognostic significance of TILs and TIL-based therapy for cervical cancer and discuss related perspectives.

Prediction of treatment response from the microenvironment of tumor immunity in cervical cancer patients treated with chemoradiotherapy

To supplement clinical decision-making in the management of cervical cancer, various prognostic factors, including tumor immune microenvironments, were examined in patients with cervical cancer treated with definitive chemoradiotherapy. We retrospectively analyzed the expression of CD8, FoxP3, HLA-1, PD-L1, and XRCC4 in 100 cases of cervical cancer. The observed tumor immune microenvironments were also classified into three types: inflamed, excluded, and cold type. Less FoxP3+ T cells and cold-type tumor were found to be poor prognostic factors in addition to non-SCC, large pre-treatment tumor volume, and three or less cycles of concurrent chemotherapy based on multivariate analysis. Cold-type tumors had significantly worse prognoses than the other two types, whereas inflamed- and excluded-type tumors showed similar 5-year disease-specific survival (P < 0.001; 0% vs. 60.3% vs. 72.3%). Radiotherapy could overcome the inhibitory immune microenvironment that occurs in excluded type. Individualized combination therapy adapted to pre-treatment tumor immunity may be necessary to improve radiotherapy outcomes in cervical cancer.

A prognostic value of CD45RA+, CD45RO+, CCL20+ and CCR6+ expressing cells as 'immunoscore' to predict cervical cancer induced by HPV

The interplay between cervical cancer (CC) and immune cells, mainly intratumoral lymphocytes, has a pivotal role in carcinogenesis. In this context, we evaluated the distribution of CD45RA⁺ and CD45RO⁺ cells as well as CCR6⁺ and CCL20⁺ cells in intraepithelial (IE) and marginal stroma (MS) areas from cervical intraepithelial neoplasia (CIN) I-III, and CC as 'immunoscore' for HPV-induced CC outcome. We observed increased CD45RA⁺ and CD45RO⁺ cells distribution in IE and MS areas in the CC group compared to CIN groups and healthy volunteers. Interestingly, there is a remarkable reduction of CCL20⁺ expressing cells distribution according to lesion severity. The CC group had a significant decrease in CCL20⁺ and CCR6⁺-expressing cells distribution in both IE and MS areas compared to all groups. Using the 'immunoscore' model, we observed an increased number of women presenting high CD45RA⁺/CD45RO⁺ and low CCL20⁺/CCR6⁺ 'immunoscore' in the CC group. Our results suggested a pattern in cervical inflammatory process with increasing CD45RA⁺/CD45RO⁺, and decreasing CCL20⁺/CCR6⁺ expression in accordance with CIN severity. Taken together, these markers could be evaluated as 'immunoscore' predictors to CC response. A more comprehensive analysis of longitudinal studies should be conducted to associate CD45RA⁺/CD45RO⁺ and CCL20⁺/CCR6⁺ 'immunoscore' to CC progression and validate its value as a prognosis method.

Analysis of radiotherapy-induced alteration of CD8+ T cells and PD-L1 expression in patients with uterine cervical squamous cell carcinoma

Radiotherapy induces an immune response in the cancer microenvironment that may influence clinical outcome. The present study aimed to analyse the alteration of CD8⁺ T-cell infiltration and programmed death-ligand 1 (PD-L1) expression following radiotherapy in clinical samples from patients with uterine cervical squamous cell carcinoma. Additionally, the current study sought to analyse the association between these immune responses and clinical outcomes. A total of 75 patients who received either definitive chemoradiotherapy or radiotherapy were retrospectively analyzed. CD8⁺ T-cell infiltration and PD-L1 expression were determined by immunohistochemistry using biopsy specimens before radiotherapy (pre-RT) and after 10 Gy radiotherapy (post-10 Gy). The PD-L1⁺ rate was significantly increased from 5% (4/75) pre-RT to 52% (39/75) post-10 Gy (P<0.01). Despite this increase in the PD-L1⁺ rate post-10 Gy, there was no significant association between both pre-RT and post-10 Gy and overall survival (OS), locoregional control (LC) and progression-free survival (PFS). On the other hand, the CD8⁺ T-cell infiltration density was significantly decreased for all patients (median, 23.1% pre-RT vs. 16.9% post-10 Gy; P=0.038); however, this tended to increase in patients treated with radiotherapy alone (median, 17.7% pre-RT vs. 24.0% post-10 Gy; P=0.400). Notably, patients with high CD8⁺ T-cell infiltration either pre-RT or post-10 Gy exhibited positive associations with OS, LC and PFS. Thus, the present analysis suggested that CD8⁺ T-cell infiltration may be a prognostic biomarker for patients with cervical cancer receiving radiotherapy. Furthermore, immune checkpoint inhibitors may be effective in patients who have received radiotherapy, since radiotherapy upregulated PD-L1 expression in cervical cancer specimens.

Immune-Inhibitory Gene Expression is Positively Correlated with Overall Immune Activity and Predicts Increased Survival Probability of Cervical and Head and Neck Cancer Patients

Background: Limited immunotherapy options are approved for the treatment of cervical cancer and only 10-25% of patients respond effectively to checkpoint inhibition monotherapy. To aid the development of novel therapeutic immune targets, we aimed to explore survival-associated immune biomarkers and co-expressed immune networks in cervical cancer. Methods: Using The Cancer Genome Atlas (TCGA) Cervical Squamous Cell Carcinoma (CESC) data (n = 304), we performed weighted gene co-expression network analysis (WGCNA), and determined which co-expressed immune-related genes and networks are associated with survival probability in CESC patients under conventional therapy. A "Pan-Immune Score" and "Immune Suppression Score" was generated based on expression of survival-associated co-expressed immune networks and immune suppressive genes, which were subsequently tested for association with survival probablity using the TCGA Head Neck Squamous Cell Carcinoma (HNSCC) data (n = 528), representing a second SCC cancer type. Results: In CESC, WGCNA identified a co-expression module enriched in immune response related genes, including 462 genes where high expression was associated with increased survival probability, and enriched for genes associated with T cell receptor, cytokine and chemokine signaling. However, a high level of expression of 43 of the genes in this module was associated with decreased survival probability but were not enriched in particular pathways. Separately, we identified 20 genes associated with immune suppression including inhibitory immune checkpoint and regulatory T cell-related genes, where high expression was associated with increased survival probability. Expression of these 20 immune suppressive genes (represented as "Immune Suppression Score") was highly correlated with expression of overall survival-associated immune genes (represented as "Pan-Immune Score"). However, high expression of seven immune suppression genes, including TWEAK-R, CD73, IL1 family and TGFb family genes, was significantly associated with decreased survival probability. Both scores also significantly associated with survival probability in HNSCC, and correlated with the previously established "Immunophenoscore." Conclusion: CESC and HNSCC tumors expressing genes predictive of T cell infiltrates (hot tumors) have a better prognosis, despite simultaneous expression of many immune inhibitory genes, than tumors lacking expression of genes associated with T cell infiltrates (cold tumors) whether or not these tumor express immune inhibitory genes.

Predictive Values of Programmed Cell Death-Ligand 1 Expression for Prognosis, Clinicopathological Factors, and Response to Programmed Cell Death-1/Programmed Cell Death-Ligand 1 Inhibitors in Patients With Gynecological Cancers: A Meta-Analysis

Background

The prognostic value of programmed cell death-ligand 1 (PD-L1) in gynecological cancers has been explored previously, but the conclusion remains controversial due to limited evidence. This study aimed to conduct an updated meta-analysis to re-investigate the predictive significance of PD-L1 expression.

Methods

PubMed, EMBASE and Cochrane Library databases were searched. The associations between PD-L1 expression status and prognosis [overall survival (OS), progression-free survival (PFS), recurrence-free survival (RFS), cancer-specific survival (CSS) or disease-free survival (DFS)], clinical parameters [FIGO stage, lymph node metastasis (LNM), tumor size, infiltration depth, lymphovascular space invasion (LVSI) or grade] and response to anti-PD-1/PD-L1 treatment [objective response rate (ORR)] were analyzed by hazard ratios (HR) or relative risks (RR).

Results

Fifty-five studies were enrolled. Overall, high PD-L1 expression was not significantly associated with OS, PFS, RFS, CSS and DFS of gynecological cancers. However, subgroup analysis of studies with reported HR (HR = 1.27) and a cut-off value of 5% (HR = 2.10) suggested that high PD-L1 expression was correlated with a shorter OS of gynecological cancer patients. Further sub-subgroup analysis revealed that high PD-L1 expressed on tumor-infiltrating immune cells (TICs) predicted a favorable OS for ovarian (HR = 0.72), but a poor OS for cervical cancer (HR = 3.44). PD-L1 overexpression was also correlated with a lower OS rate in non-Asian endometrial cancer (HR = 1.60). High level of PD-L1 was only clinically correlated with a shorter PFS in Asian endometrial cancer (HR = 1.59). Furthermore, PD-L1-positivity was correlated with LNM (for overall, ovarian and endometrial cancer expressed on tumor cells), advanced FIGO stage (for overall, ovarian cancer expressed on tumor cells, endometrial cancer expressed on tumor cells and TICs), LVSI (for overall and endometrial cancer expressed on tumor cells and TICs), and increasing infiltration depth/high grade (only for endometrial cancer expressed on TICs). Patients with PD-L1-positivity may obtain more benefit from anti-PD-1/PD-L1 treatment than the negative group, showing a higher ORR (RR = 1.98), longer OS (HR = 0.34) and PFS (HR = 0.61).

Conclusion

Our findings suggest high PD-L1 expression may be a suitable biomarker for predicting the clinical outcomes in patients with gynecological cancers.

Immunotyping and Quantification of Melanoma Tumor-Infiltrating Lymphocytes

The density of tumour-infiltrating lymphocytes (TILs) in melanoma is correlated with improved clinical prognosis; however, standardized TIL immunotyping and quantification protocols are lacking. Herein, we provide a review of the technologies being utilized for the immunotyping and quantification of melanoma TILs.

PD-L1 in Combination with CD8+TIL and HIF-1α are Promising Prognosis Predictors of Head and Neck Squamous Cell Carcinoma

Objective

The aim of this study was to evaluate the prognosis effect of PD-L1 in combination with CD8⁺ tumor-infiltrating lymphocyte (TIL) or HIF-1α in head and neck squamous cell carcinoma (HNSCC).

Methods

A total of 63 patients who underwent surgical resection were included in this study. The level of PD-L1, CD8⁺ TIL, and HIF-1α was determined by immunohistochemical analysis. The survival of patients was evaluated by Kaplan–Meier analysis. The prognostic power of these parameters was evaluated by C-index.

Results

We observed that the survival of patients, who had a high level of PD-L1 in tumor cells, was significantly shorter than those who had a low level of PD-L1. However, the survival of patients who had a high level of PD-L1 in tumor microenvironment was significantly longer than patients with a low level of PD-L1 in tumor microenvironment. In addition, high level of CD8⁺ tumor-infiltrating lymphocyte or low level of HIF-1α level suggests a better prognosis. Moreover, we observed that PD-L1 in combination with CD8⁺ tumor-infiltrating lymphocyte and HIF-1α could significantly improve the prognostic effect of current TNM stage.

Conclusion

The results of this study suggest that the level of PD-L1, CD8⁺TIL, and HIF-1α are useful prognostic biomarkers for patients with HNSCC. Incorporating these biomarkers into current TNM stage of HNSCC improve the discriminatory capability of TNM stage.

Association between cancer immunity and treatment results in uterine cervical cancer patients treated with radiotherapy

OBJECTIVE

To evaluate proteins related to tumor immune response and treatment outcome from radiotherapy for uterine cervical cancer patients.

METHODS

We performed a retrospective immunohistochemical staining of 81 patients with uterine cervical cancer who underwent definitive radiotherapy. We examined the expression of programmed death ligand 1, human leukocyte antigen class I, tumor-infiltrating CD8+, and forkhead box P3+ (FoxP3+) T cells in tumor tissues.

RESULTS

In biopsy specimen, patients with a higher number of CD8+ T cells and FoxP3+ T cells had a better disease-specific survival than patients with a lower number of CD8+ T cells and FoxP3+ cells (P = 0.018 and P = 0.009). Multivariate analysis showed that equivalent dose in 2 Gy fractions (EQD2) of the minimum dose to 90% of the high-risk clinical target volume, FoxP3+ T cells and expression of human leukocyte antigen class I were significant prognostic factors. When the EQD2 is 70 Gy or more, a higher local control rate is obtained regardless of the number of CD8- or FoxP3-positive cells. When EQD2 is <70 Gy, the number of CD8-positive cells has a significant impact on treatment outcome: the recurrence rate (local recurrence rate + distant metastasis rate) was 46.2% in the group with a CD8 value of 230 or higher, whereas the recurrence rate was 75.7% in the group with a CD8 value of less than 230.

CONCLUSION

The combination of CD8 or FoxP3 with EQD2 can be potentially useful to predict the treatment results of radiotherapy for cervical cancer, leading to individualized optimal selection of treatment for cervical cancer.

Role of the Neutrophil in the Pathogenesis of Advanced Cancer and Impaired Responsiveness to Therapy

Notwithstanding the well-recognized involvement of chronic neutrophilic inflammation in the initiation phase of many types of epithelial cancers, a growing body of evidence has also implicated these cells in the pathogenesis of the later phases of cancer development, specifically progression and spread. In this setting, established tumors have a propensity to induce myelopoiesis and to recruit neutrophils to the tumor microenvironment (TME), where these cells undergo reprogramming and transitioning to myeloid-derived suppressor cells (MDSCs) with a pro-tumorigenic phenotype. In the TME, these MDSCs, via the production of a broad range of mediators, not only attenuate the anti-tumor activity of tumor-infiltrating lymphocytes, but also exclude these cells from the TME. Realization of the pro-tumorigenic activities of MDSCs of neutrophilic origin has resulted in the development of a range of adjunctive strategies targeting the recruitment of these cells and/or the harmful activities of their mediators of immunosuppression. Most of these are in the pre-clinical or very early clinical stages of evaluation. Notable exceptions, however, are several pharmacologic, allosteric inhibitors of neutrophil/MDSC CXCR1/2 receptors. These agents have entered late-stage clinical assessment as adjuncts to either chemotherapy or inhibitory immune checkpoint-targeted therapy in patients with various types of advanced malignancy. The current review updates the origins and identities of MDSCs of neutrophilic origin and their spectrum of immunosuppressive mediators, as well as current and pipeline MDSC-targeted strategies as potential adjuncts to cancer therapies. These sections are preceded by a consideration of the carcinogenic potential of neutrophils.

Tumor Size Matters-Understanding Concomitant Tumor Immunity in the Context of Hypofractionated Radiotherapy with Immunotherapy

The purpose of this study was to determine the dynamic contributions of different immune cell subsets to primary and abscopal tumor regression after hypofractionated radiation therapy (hRT) and the impact of anti-PD-1 therapy. A bilateral syngeneic FSA1 fibrosarcoma model was used in immunocompetent C3H mice, with delayed inoculation to mimic primary and microscopic disease. The effect of tumor burden on intratumoral and splenic immune cell content was delineated as a prelude to hRT on macroscopic T1 tumors with 3 fractions of 8 Gy while microscopic T2 tumors were left untreated. This was performed with and without systemic anti-PD-1. Immune profiles within T1 and T2 tumors and in spleen changed drastically with tumor burden in untreated mice with infiltrating CD4+ content declining, while the proportion of CD4+ Tregs rose. Myeloid cell representation escalated in larger tumors, resulting in major decreases in the lymphoid:myeloid ratios. In general, activation of Tregs and myeloid-derived suppressor cells allow immunogenic tumors to grow, although their relative contributions change with time. The evidence suggests that primary T1 tumors self-regulate their immune content depending on their size and this can influence the lymphoid compartment of T2 tumors, especially with respect to Tregs. Tumor burden is a major confounding factor in immune analysis that has to be taken into consideration in experimental models and in the clinic. hRT caused complete local regression of primary tumors, which was accompanied by heavy infiltration of CD8+ T cells activated to express IFN-γ and PD-1; while certain myeloid populations diminished. In spite of this active infiltrate, primary hRT failed to generate the systemic conditions required to cause abscopal regression of unirradiated microscopic tumors unless PD-1 blockade, which on its own was ineffective, was added to the RT regimen. The combination further increased local and systemically activated CD8+ T cells, but few other changes. This study emphasizes the subtle interplay between the immune system and tumors as they grow and how difficult it is for local RT, which can generate a local immune response that may help with primary tumor regression, to overcome the systemic barriers that are generated so as to effect immune regression of even small abscopal lesions.