Cancer Testis Research Articles

High-affinity T cell receptor ImmTAC® bispecific efficiently redirects T cells to kill tumor cells expressing the cancer testis antigen PRAME

Abstract PRAME (Preferentially expressed Antigen in Melanoma) is a cancer testis antigen expressed in several tumor indications, representing an attractive anti-cancer target. However, its intracellular location limits targeting by traditional methods. PRAME peptides are presented on the surface of tumor cells by human leukocyte antigen (HLA) molecules, indicating that a T cell receptor (TCR)-based strategy that redirects T cells to kill PRAME+ tumors could be a novel immunotherapeutic option. We confirm that PRAME protein is expressed in cutaneous melanoma, including rare subtypes with limited treatment options, as well as primary and metastatic lung, breast, endometrial and ovarian tumors. Furthermore, PRAME is expressed homogeneously across tumors with distinct oncogenic mutations, mutation burden, PD-L1 expression, immune infiltration and features of immune checkpoint resistance. Immunopeptidomic analysis of primary tumors detected HLA class I-restricted PRAME peptides. A TCR recognizing PRAME peptide SLLQHLIGL was engineered to high affinity and fused to a CD3 engaging domain to create a TCRxCD3 bispecific molecule (Immune mobilizing monoclonal TCR Against Cancer, ImmTAC®) with the ability to redirect polyclonal T cells to efficiently kill PRAME+ cells. The degree of T cell activation was positively correlated with peptide-HLA abundance, with as few as 10 epitopes per cell sufficient for target cell killing. Impaired ImmTAC®-redirected cytotoxicity of exhausted T cells was rescued using an anti-PD-1 antibody, supporting the use of a combination strategy to treat tumors with active PDL1-PD1 axes. Our data demonstrate selective and efficient T cell activation and killing by a PRAME-directed TCRxCD3 bispecific, supporting further investigation in multiple cancer indications.

Enhanced immune responses are accompanied by increased MAGEA expression in osteosarcoma metastases

ObjectiveOsteosarcoma is the most common primary bone sarcoma. About 50% of patients develop metastatic disease and their 5-year survival lingers at around 20%–30%. T cell checkpoint blockade immunotherapies have revolutionised cancer treatment in the last decade, but their impact remains limited in osteosarcoma.Methods and analysisIn order to reveal potentially novel immunotherapeutic strategies for advanced osteosarcoma, we conducted an immunogenomic characterisation of a unique sample set comprising 30 osteosarcoma samples from seven patients, collected throughout disease progression. We performed RNA-sequencing and imaging mass cytometry analysis on these samples to reveal the immunological landscape during osteosarcoma progression.ResultsTranscriptional and phenotypical hallmarks of cytotoxic T cell-driven anticancer immunity were enriched in metastatic lesions as compared with primary tumours. Spatial analysis showed T cells infiltrating central regions of osteosarcoma metastases, indicating the absence of an immune excluded environment. In parallel, we found a pronounced increase in the expression of cancer testis antigens, particularly melanoma antigen family A (MAGEA)-related antigens, in osteosarcoma metastases, which was validated in an independent cohort (N=91). In addition, we demonstrated the presentation of MAGE-derived peptides in three out of four osteosarcoma cell lines.ConclusionThese findings indicate a concurrent augmentation of cytotoxic antitumour immune responses and expression of MAGEA antigens from primary to metastatic osteosarcoma. This observation suggests the exploration of MAGEA antigens as potential targets for immunotherapy in the treatment of advanced osteosarcoma.

The Utilization of PRAME in the Diagnosis, Prognosis, and Treatment of Melanoma.

Melanoma, a deadly form of skin cancer, has seen improved survival rates due to advances in diagnosis and treatment, yet the need for further improvement remains critical. Tumor-associated antigens, such as PRAME (Preferentially Expressed Antigen in Melanoma), offer promising avenues for enhanced diagnostic precision, prognostic assessment, and targeted immunotherapy. PRAME, a cancer testis antigen, is selectively expressed in various cancers, including melanoma, and plays a key role in promoting tumorigenesis through inhibition of retinoic acid signaling, epithelial-to-mesenchymal transition, and immune evasion. This review explores the diagnostic utility of PRAME in distinguishing melanoma from benign nevi, its prognostic value in aggressive melanoma subtypes, and its potential as a therapeutic target in cancer vaccines and adoptive T-cell therapies. While PRAME-targeted therapies face challenges such as tumor heterogeneity and immune suppression, ongoing research aims to overcome these barriers, offering hope for more effective melanoma treatments.

CD8 + T-cells restrict the development of peritoneal metastasis and support the efficacy of hyperthermic intraperitoneal chemotherapy (HIPEC)

Multimodal therapy for peritoneal metastasis (PM) including cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) provides long-term survival in highly selected colorectal cancer patients. Mechanisms behind HIPEC are unknown and may include induction of adaptive immunity. We therefore analyzed human PM samples and explored the impact of HIPEC in experimental models. Human samples from colorectal primary tumors (n = 19) and PM lesions (n = 37) were examined for the presence of CD8 + T-cells and their association with disease free (DFS) and overall survival (OS). CD8 + T cell response after HIPEC was assessed using an in-vivo PM mouse model, tumor cell lines and patient-derived tumor organoids. Patients with high intraepithelial CD8 + T cell counts showed longer DFS and OS. In the mouse model, HIPEC controlled growth of PM and increased numbers of functional granzyme positive CD8 + T cells within tumors. Cell lines and human organoids that were treated with heated chemotherapies showed immunogenic changes, reflected by significantly higher levels of MHC-class I molecules and expression of Cancer Testis Antigens Cyclin A1 and SSX-4. Using in-vitro co-culture assays, we noticed that cancer cells treated with heated chemotherapy primed dendritic cells, which subsequently enhanced effector functions of CD8 + T cells. The presence of CD8 + T-cells within PM lesions is associated with prolonged survival of patients with PM. Data from PM mouse model and in-vitro assay show that heated chemotherapies induce immunogenic changes on cancer cells leading to induction of CD8 + T-cells mediated immunity, which seems to control growth of PM lesions in mice after HIPEC.

Expression of cancer testis genes in gastric neoplasms — a preliminary study

Expression of cancer testis genes in gastric neoplasms — a preliminary study

Brief Communication on MAGE-A4 and Coexpression of Cancer Testis Antigens in Metastatic Synovial Sarcomas: Considerations for Development of Immunotherapeutics.

Therapeutic options for synovial sarcoma (SyS) have not evolved for several decades and the efficacy of second-line treatments is very limited. The expression of a large family of proteins known as cancer testis antigens (CTAs) in SyS has spurred the development of targeted T-cell therapies currently in clinical trials, such as those aimed at melanoma-associated antigen (MAGE)-A4 and New York esophageal squamous cell carcinoma 1 (NY-ESO-1), which have shown promising clinical efficacy. Extensive knowledge of the prevalence of expression and coexpression of CTAs is critical to design T-cell therapies with optimal coverage of the patient population. We analyzed the expression of CTAs of the MAGE-A family as well as NY-ESO-1 and preferentially expressed antigen in melanoma (PRAME) by RNA sequencing in a large cohort of 133 SyS samples from patients registered in the French sarcoma database (NETSARC+). Among MAGE-As, MAGE-A4 had the highest prevalence (65%), followed by MAGE-A10 (15%) and MAGE-A9 (13%). Almost all samples (92%) expressing any of the MAGE-As also expressed MAGE-A4. NY-ESO-1 was expressed in 65% of samples, with a large but incomplete overlap with MAGE-A4, whereas PRAME was present in 121 (91%) samples. Complementary immunohistochemical analyses were used to establish the positive correlation between RNA and protein expression for MAGE-A4 and NY-ESO-1. These data inform the strategy for optimal coverage of the SyS patient population with T-cell therapies, offering patients with SyS new options for single or combined second lines of treatment.

T Cell-Engaging Bispecific Antibodies Targeting gp100 and PRAME: Expanding Application from Uveal Melanoma to Cutaneous Melanoma.

Uveal melanoma represents a rare and aggressive subtype of melanoma with limited treatment options and poor prognosis, especially in the metastatic setting. Tebentafusp, a bispecific fusion protein, offers a promising therapeutic approach by targeting gp100, an antigen highly expressed in uveal melanoma cells, and redirecting T cell-mediated cytotoxicity towards tumor cells. This review provides an overview of the preclinical and clinical data on tebentafusp in the management of metastatic uveal melanoma. We summarize the mechanism of action, clinical efficacy, safety profile, and ongoing research efforts surrounding this innovative immunotherapy. Preclinical studies have demonstrated the ability of tebentafusp to induce potent and specific anti-tumor immune responses against gp100-expressing uveal melanoma cells. Clinical trials have shown encouraging results, with tebentafusp exhibiting meaningful clinical activity in a subset of patients with metastatic uveal melanoma. Importantly, tebentafusp has also demonstrated a manageable safety profile. By specifically targeting tumor cells expressing gp100, tebentafusp offers a promising therapeutic avenue for individuals with metastatic uveal melanoma, meeting a significant clinical need in this context. Continued clinical trials will provide additional insights into the impact of tebentafusp on treatment-resistant metastatic cutaneous melanoma. Furthermore, we are exploring the potential of T cell engagers directed against the cancer testis antigen PRAME, which could have widespread utility in the treatment of cutaneous melanoma as well as other PRAME-expressing malignancies.

Irreversible electroporation of localised prostate cancerdownregulates immune suppression andinduces systemic anti-tumour T-cell activation - IRE-IMMUNO study.

To prospectively compare systemic anti-tumour immune responses induced by irreversible electroporation (IRE) and robot-assisted radical prostatectomy (RARP) in patients with localised intermediate-risk prostate cancer (PCa). Between February 2021 and June 2022, before and after treatment (at 5, 14 and 30 days) peripheral blood samples of 30 patients with localised PCa were prospectively collected. Patient inclusion criteria were: International Society of Urological Pathologists Grade 2-3, clinical cancer stage ≤T2c, prostate-specific antigen level <20 ng/mL). Patients were treated with IRE (n = 20) or RARP (n = 10). Frequency and activation status of lymphocytic and myeloid immune cell subsets were determined using flow cytometry. PCa-specific T-cell responses to prostatic acid phosphatase(PSAP) and cancer testis antigen (New York oesophageal squamous cell carcinoma 1 [NY-ESO-1]) were determined by interferon-γ enzyme-linked immunospot assay (ELISpot). Repeated-measures analysis of variance and two-sided Student's t-tests were used to compare immune responses over time and between treatment cohorts. Patient and tumour characteristics were similar between the cohorts except for age (median 68 years [IRE] and 62 years [RARP], P = 0.01). IRE induced depletion of systemic regulatory Tcells (P = 0.0001) and a simultaneous increase in activated cytotoxic T-lymphocyte antigen 4 (CTLA-4)+ cluster of differentiation (CD)4+ (P < 0.001) and CD8+ (P = 0.032) Tcells, consistent with reduction of systemic immune suppression allowing for effector T-cell activation, peaking 14 days after IRE. Effects were positively correlated with tumour volume/ablation size. Accordingly, IRE induced expansion of PSAP and/or NY-ESO-1 specific T-cell responses in four of the eight immune competent patients. Temporarily increased activated myeloid derived suppressor cell frequencies (P = 0.047) were consistent with transient immunosuppression after RARP. Irreversible electroporation induces a PCa-specific systemic immune response in patients with localised PCa, aiding conversion of the tumour microenvironment into a more immune permissive state. Therapeutic efficacy might be further enhanced by combination with CTLA-4 checkpoint inhibition, potentially opening up a new synergistic treatment paradigm for high-risk localised or (oligo)metastatic disease.

Potentially actionable targets in synovial sarcoma: A tissue microarray study

BackgroundSynovial sarcoma (SynSa) is one of the most common translocation-related soft tissue sarcomas. Patients with metastatic SynSa have limited treatment options and a very poor prognosis. Several novel experimental therapies are currently being explored in clinical trials, including T cell-based therapies targeting cancer testis antigens such as New York esophageal squamous cell carcinoma 1 (NY-ESO-1) or melanoma-associated antigen A4 (MAGE-A4), and degraders targeting bromodomain-containing protein 9 (BRD9). Preclinical studies investigate inhibitors of Yes associated protein 1 (YAP1), transcriptional co-activator with PDZ-binding motif (TAZ) and inhibitors of chemokine receptor 4 (CXCR4). MethodsWe explored the immunohistochemical expression of these targets using a tissue microarray (TMA) constructed from 91 clinical SynSa samples and correlated these findings with corresponding clinicopathological data. ResultsExpression of MAGE-A4 and NY-ESO-1 was found in 69 % and 56 % of the samples, respectively. NY-ESO-1 was statistically higher expressed in samples from metastatic lesions as compared to samples from primary tumors. Nuclear expression of YAP1 and TAZ was observed in 92 % and 51 % of the samples, respectively. CXCR4 was expressed in the majority of the samples (82 %). BRD9 was highly expressed in all specimens. No prognostic role could be identified for any of the investigated proteins. ConclusionThis study is a comprehensive study providing real-world data on the expression of several actionable proteins in a large proportion of SynSa samples. All evaluated markers were expressed in a clinically meaningful proportion of cases represented in our TMA, supporting the relevance of ongoing preclinical and clinical research with novel agents directed against these targets.

The LDHC-STAT3 Signaling Network Is a Key Regulator of Basal-like Breast Cancer Cell Survival.

Breast cancer treatment has evolved drastically with the addition of immunotherapy and novel targeted drugs to the current treatment options. However, achieving long-term responses with minimal adverse events remains challenging. Cancer testis antigens (CTAs) offer novel opportunities for drug development thanks to their tumor specificity, immunogenicity, pro-tumorigenic functions, and negative prognostic connotations. We previously reported that lactate dehydrogenase C (LDHC) plays a key role in regulating genomic stability and that targeting LDHC significantly improved treatment response to DNA damage response drugs in breast cancer. Here, we explored the molecular mechanisms associated with LDHC silencing in two basal-like breast cancer cell lines, MDA-MB-468 and BT-549, and a Her2-enriched breast cancer cell line, HCC-1954. Transcriptomic analyses identified the cell line-dependent differential activation of the pro-survival STAT3 pathway following LDHC depletion. While LDHC silencing significantly compromised cell survival in basal-like breast cancer cells in conjunction with a downregulation of STAT3 signaling, the opposite effect was observed in Her2-enriched breast cancer cells, which demonstrated the enhanced activation of the pro-survival STAT3 signaling pathway. The inhibition of STAT3 not only reversed the unfavorable effect of LDHC silencing in the Her2-enriched cancer cells but also demonstrated significant anti-cancer activity when used as a single agent. Our findings suggest that the LDHC-STAT3 signaling axis plays a role in regulating breast tumor cell survival in a subtype-dependent manner. Thus, LDHC-targeted therapy could be a viable therapeutic approach for a subset of breast cancer patients, particularly patients with basal-like breast cancer, whereas patients carrying Her2-enriched tumors may likely benefit more from monotherapy with STAT3 inhibitors.

The molecular landscape of PIWIL1 expression in colorectal adenocarcinoma (CRC).

3546 Background: PIWIL1 is a cancer testis antigen overexpressed in solid tumors, particularly CRC, and is associated with advanced stage and poor prognosis. It is potentially a new therapeutic target as PIWIL1 is not expressed in adult somatic tissue. A novel T cell receptor/PIWIL1 bispecific antibody is in development, restricted to individuals with human leukocyte antigen (HLA) A-02. We sought to characterize the molecular landscape of PIWIL1 in CRC. Methods: 26,581 CRC tumors were tested by next-generation sequencing (NGS) on DNA (592-gene or whole exome [WES]) and RNA (whole transcriptome [WTS]) at Caris Life Sciences (Phoenix, AZ). dMMR/MSI-H was tested by immunohistochemistry (IHC) and NGS, HLA genotypes by WES and PD-L1 by IHC (SP142, 2+, 5%). Tumor mutational burden (TMB) high was defined as ≥ 10 mt/Mb. RNA expression was used to estimate the tumor microenvironment using QuantiSEQ and RNA signatures (interferon gamma [IFNγ]; T-cell inflamed [TIS]) predictive of immune checkpoint blockade (IO) response. The top (H) and bottom (L) quartiles of PIWIL1 expression were compared using Chi-square/Fisher-Exact, and significance was determined as p adjusted for multiple comparisons (Q&lt;0.05). Real-world overall survival (rwOS) was obtained from insurance claims and calculated from tissue collection to last contact. Results: Patients with PIWIL1-H were older (median age 65 v 61, Q&lt;0.01) and more likely to be female (50.8% v 41.3%, Q&lt;0.01), compared to PIWIL1-L. PIWIL1 median expression was higher in right- v left-sided primary tumors (2.0 v 1.3 transcripts per million [TPM], Q&lt;0.05). No significant difference in PIWIL1 expression was observed among HLA genotypes. dMMR/MSI-H, TMB-H and PD-L1+ were higher in PIWIL1-H v PIWIL1-L (13.9% v 6.5%, 17.6% v 10.4%, 6.4% v 3.4%, all Q&lt;0.05). IO-related gene expression ( LAG3, IDO1, CTLA4 and others) were positively associated with PIWIL1 expression (fold change [FC]: 1.4-2.7, Q&lt;0.05). High IFNγ and TIS were associated with PIWIL1-H (Q&lt;0.001). PIWIL1 expression showed a positive association with infiltration of neutrophils, monocytes, CD4+T, dendritic and NK cells (FC: 1.3-2.9, Q&lt;0.05) while Tregs and M1 macrophages had a negative association (0.8-0.9, Q&lt;0.05). In pMMR/MSS CRC, KRAS, BRAF and TP53 mutations and loss of heterozygosity were higher in PIWIL1-H v PIWIL1-L (81% v 69%, 53% v 41%, 16% v 3%, 14% v 10%, all Q&lt;0.05) but not for PIK3CAmutations (14% v 17%). For rwOS, PIWIL1-H had longer median OS than PIWIL1-L, 31.2 v 28.8 months (HR 0.95; 95% CI 0.90-0.99, p=0.043). There was no significant rwOS difference observed in IO-treated tumors. Conclusions: PIWIL1-H CRC is associated with higher rates of dMMR/MSI-H, TMB-H and PD-L1+ as well as IO-related gene expression and signatures that are predictive of response to IO. These data suggest the PIWIL1-H subpopulation could potentially derive substantial benefit from PIWIL1-targeted immunotherapy which should be evaluated in clinical trials.

Evaluating tumor inflammation and PD-L1 expression in sequential biopsies of real-world primary and metastatic breast cancer.

e13035 Background: Biomarkers for measuring immunogenicity of tumors such as PD-L1 immunohistochemistry (IHC), tumor mutational burden (TMB), and immune gene expression have been studied in many cancers including breast cancer. How these biomarkers change over time and how their detection differs with sequential testing in the real-world clinical setting has been studied to a lesser extent but is an important consideration for optimal patient care. Methods: We performed an analysis of 30 patients with primary and metastatic breast cancer sequentially tested by comprehensive genomic and immune profiling (CGIP) at two time points during routine clinical care to observe temporal changes in immunotherapy markers and immune gene expression. Genomic variants and TMB were assessed with DNA-seq, while immune gene expression was assessed with RNA-seq. PD-L1 expression was determined using IHC. Immune gene expression signatures characterizing the tumor microenvironment (TME) were calculated, including tumor inflammation (TIGS), cell proliferation (CP), and cancer testis antigen burden (CTAB). Differences between sequential tests were tested for using linear mixed effect models. Results: Time between biopsies for sequential tests ranged from the same day to 4.5 years, with 40% of specimens being collected within 30 days of the first. Sequential specimens were collected from breast (27%), non-breast (40%), or a mix of breast and non-breast (33%) tissue. Non-breast tissue types included sites from lymph node (18%), GI tract (15%), skin (10%), thorax (7%), and musculoskeletal sites (7%). Overall, TMB, PD-L1 IHC, and gene expression signatures were relatively stable between sequential tests (P &gt; 0.05); however, trends were noted for second tests detecting lower tumor inflammation (TIGS score) and PD-L1 IHC (P = 0.1). Further, second tests detected significantly lower levels of tumor inflammation when both were performed on non-breast tissue (P = 0.04), but not when performed on all breast (P = 0.7) or a mix of breast and non-breast (P = 0.6) tissues. An opposite trend was noted for PD-L1 where second tests detected lower levels of PD-L1 IHC when both tests were performed on breast tissue (P = 0.1), but not when performed on all non-breast (P = 0.4) or a mix of breast and non-breast (P = 0.5) tissue. Tissue-dependent trends were still present even when excluding lymph node specimens (P = 0.1). Conclusions: Changes in immunotherapy markers and immune gene expression signatures, on average, remained relatively stable over time, except for tumor inflammation and PD-L1 IHC when sequentially testing all non-breast or breast tissue, respectively. These observations highlight the utility of clinical CGIP testing in revealing temporal changes of the TME, which may help inform clinical trial or treatment strategies occurring over time for primary and metastatic breast cancer.

Testis-specific serine kinase 6 (TSSK6) is abnormally expressed in colorectal cancer and promotes oncogenic behaviors

Cancer testis antigens (CTAs) are a collection of proteins whose expression is normally restricted to the gamete, but abnormally activated in a wide variety of tumors. The CTA, Testis specific serine kinase 6 (TSSK6), is essential for male fertility in mice. Functional relevance of TSSK6 to cancer, if any, has not previously been investigated. Here we find that TSSK6 is frequently anomalously expressed in colorectal cancer and patients with elevated TSSK6 expression have reduced relapse free survival. Depletion of TSSK6 from colorectal cancer cells attenuates anchorage independent growth, invasion and growth in vivo. Conversely, overexpression of TSSK6 enhances anchorage independence and invasion in vitro as well as in vivo tumor growth. Notably, ectopic expression of TSSK6 in semi-transformed human colonic epithelial cells is sufficient to confer anchorage independence and enhance invasion. In somatic cells, TSSK6 co-localizes with and enhances the formation of paxillin and tensin positive foci at the cell periphery, suggesting a function in focal adhesion formation. Importantly, TSSK6 kinase activity is essential to induce these tumorigenic behaviors. Our findings establish that TSSK6 exhibits oncogenic activity when abnormally expressed in colorectal cancer cells. Thus, TSSK6 is a previously unrecognized intervention target for therapy, which could exhibit an exceptionally broad therapeutic window.

Abstract PO4-16-04: Decoding the immune landscape of breast cancer (BC) during pregnancy (PrBC): Impact of hormone receptors (HR) and tumor-infiltrating lymphocytes (TILs) phenotype on gene expression signatures

Abstract Introduction: PrBC is an uncommon malignancy with aggressive behavior. Its pathogenesis involves distinct immune mechanisms associated with maternal-fetal tolerance and tumor-host immunoediting. PrBC displays specific patterns of TILs with increased CD8+ cells. Gaining a comprehensive understanding of the molecular processes underlying this immune synergy is crucial for enhancing PrBC patients’ clinical management. Here, we sought to identify dysregulated immune-related genes in PrBC and explore their association with HR status and TILs. Methods: A total of n=75 PrBC (age range 26-43 years) and n=67 age-matched early-onset breast cancer (EOBC) in non-pregnant women (controls; age range 28-43 years) were selected from our Institutional registry. For all cases TILs were quantified according to the International TILs Working Group recommendations and profiled by IHC for CD4 and CD8. RNA was extracted from representative FFPE tissue blocks to perform the expression analysis of 395 genes involved in tumor-immune interactions using a targeted NGS panel (Oncomine™ Immune Response Research Assay, Thermofisher). Samples with &amp;gt;1,000,000 mapped reads and &amp;gt;800,000 valid reads were considered adequate. R package DESeq2 software 1.38.3 was used for sequencing depth differences normalization and differential gene expression analysis. Differentially expressed genes (DEGs) were identified based on a significant p-value (p&amp;lt; 0.05). Results: The comparison between PrBC and EOBC revealed a total of n=7 DEGs. All of these genes were upregulated and belonged to distinct superfamilies, including Cancer/Testis (CT) Antigen (MAGEA1/3, XAGE1B), Interferons/Cytokines (IFNA17, IFNB1), Chemokines (CXCL13), and Immunoglobulin (PECAM1/CD31). Notably, the upregulation of Chemokines in respect to EOBC was observed exclusively in HR+ PrBC, whereas triple-negative (TN) PrBC did not exhibit this pattern compared to the control group. Hence, the upregulation of ALOX15B, an enzyme involved in fatty acid peroxidation, was specific to TN PrBC. The immune signatures showed significant variations between PrBC and EOBC also based on TILs density and subpopulations. Indeed, the upregulation of CT genes (MAGEA1, XAGE1B) was exclusively observed in PrBC cases characterized by low TILs levels and prevalence of CD8+ or CD4+ cells. Finally, CD4+ TILs were absent or low in PrBC with upregulated Interferons, Cytokines, Chemokines, and Immunoglobulin genes, but present in cases with increased expression of CT and KLRF1 (NK cells). Conclusion: These findings highlight the heterogeneity and distinct molecular characteristics of PrBC and EOBC. The upregulation of specific immune-related gene families, such as CT and Chemokines, in different PrBC subtypes may suggest their potential role as actionable biomarkers (e.g. MAGEA, a well-known oncogene and potential immunotherapy target). The differences in immune signatures and TILs subpopulations further emphasize the importance of the immune microenvironment in PrBC biology and behavior. Future studies could delve deeper into the clinical implications of these gene expression patterns and explore their relevance in personalized treatment strategies for PrBC. Citation Format: Konstantinos Venetis, Elham Sajjadi, Chiara Frascarelli, Mariia Ivanova, Marianna D'Ercole, Concetta Blundo, Massimo Giroda, Eugenia Di Loreto, Giovanna Scarfone, Stefano Ferrero, Paolo Veronesi, Viviana Galimberti, Fedro Alessandro Peccatori, Nicola Fusco, Elena Guerini-Rocco. Decoding the immune landscape of breast cancer (BC) during pregnancy (PrBC): Impact of hormone receptors (HR) and tumor-infiltrating lymphocytes (TILs) phenotype on gene expression signatures [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-16-04.

Abstract PO4-25-03: Comprehensive immune profiling reveals factors associated with neoadjuvant chemotherapy response in triple negative breast cancer

Abstract Background: KEYNOTE-522 has resulted in FDA approval of the immune checkpoint blocker pembrolizumab with neoadjuvant chemotherapy for patients with high-risk triple negative breast cancer (TNBC), given the remarkable improvement in pCR rate to 65% along with improvement in event free survival, while with chemotherapy alone, the pCR rate is 40-50%. Unfortunately, use of pembrolizumab is associated with several immune related adverse events (irAE), some of which can be life-threatening and debilitating, including cardiomyositis, encephalitis, and adrenal insufficiency, among others. Hence, there is an unmet need to identify biomarkers in the tumor microenvironment which could predict patients who may attain pCR with chemotherapy alone and be spared the side effects from the added PD-1 inhibition. Methods: Comprehensive immune profiling, including PD-L1 IHC and the expression of 395 immune genes by RNA-seq, was performed on 1:2 matched FFPE tumor samples from 23 stage 1-3 TNBC patients (2 stage 1, 6 stage 2, 15 stage 3). All patients were female with an average age of 48 years (range: 25-79 years). 14 patients were treated with neoadjuvant chemotherapy alone (NAC) and 9 were treated with neoadjuvant chemotherapy combined with the checkpoint inhibitor pembrolizumab (NAC+I). mRNA expression signatures of tumor inflammation (TIGS, weak/moderate/strong), cell proliferation (CP, poor/moderate/high), and cancer testis antigen expression burden (CTAB) were determined by RNA-sequencing. Statistical comparisons of quantitative biomarkers between groups were calculated using the Wilcoxon Rank-Sum test, overrepresentation analysis of categorical variables between groups was calculated by proportions test, and survival differences were quantified by Cox proportional hazards analysis. Pathological responses were documented as pathological complete response (pCR) vs. non-pCR. Results: Across the entire cohort, patients with a BMI &amp;lt; 30 had significantly higher PD-L1 expression (assessed by RNA) than those with a BMI ³ 30 [p=0.047]. While not a statistically significant association, the NAC+I group tended to have a higher pCR rate compared to the NAC group [44.4% vs. 28.6%, p=0.66]. Across the entire cohort, tumors with high CTA expression, designated as CTAB high, had a higher pCR rate than CTAB low tumors [54.5% vs 16.7%, p=0.089]. No significant difference in pCR rate between TIGS or CP groups was detected for the NAC group, but in the NAC+I group, highly proliferative tumors had a lower pCR rate than moderately proliferative tumors [0% vs. 80%, p=0.048]. The pCR and non-pCR groups for each treatment type also exhibited distinct gene expression profiles. Among the NAC group, underexpression of FOXP3 and overexpression of MAPK14 and CD44 were associated with pCR [p≤0.031], while underexpression of IFNB1, MAPK14, and CD44 was associated with non-pCR [p≤0.029]. Among the NAC+I group, overexpression of CXCR4, TNFR and CCL20 was associated with non-pCR [p≤0.046]. Interestingly, SDHA was significantly overexpressed in the non-pCR subset of patients in the NAC group and significantly underexpressed in the non-pCR subset of patients in the NAC+I group [p≤0.031]. Conclusions: The development of biomarkers of treatment response is essential to the integration of immunotherapy with chemotherapy as a combined cancer treatment. Our study profiled the immune context of both NAC and NAC+I and identified several key microenvironmental differences underlying divergent treatment response in both groups. A comprehensive understanding of these factors could potentially predict pCR to chemotherapy alone, enabling the avoidance of the unnecessary treatment of these tumors with immunotherapy. Citation Format: Robert Seager, Heidi Ko, Sarabjot Pabla, Maria-Fernanda Senosain, Pawel Kalinski, Erik Van Roey, Shuang Gao, Kyle Strickland, Rebecca Previs, Mary Nesline, Stephanie Hastings, Shengle Zhang, Jeffrey Conroy, Taylor Jensen, Marcia Eisenberg, Brian Caveney, Eric Severson, Shakti Ramkissoon, Shipra Gandhi. Comprehensive immune profiling reveals factors associated with neoadjuvant chemotherapy response in triple negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-25-03.

Immunologic Factors Associated with Differential Response to Neoadjuvant Chemoimmunotherapy in Triple-Negative Breast Cancer.

Background: KEYNOTE-522 resulted in FDA approval of the immune checkpoint inhibitor pembrolizumab in combination with neoadjuvant chemotherapy for patients with early-stage, high-risk, triple-negative breast cancer (TNBC). Unfortunately, pembrolizumab is associated with several immune-related adverse events (irAEs). We aimed to identify potential tumor microenvironment (TME) biomarkers which could predict patients who may attain pathological complete response (pCR) with chemotherapy alone and be spared the use of anti-PD-1 immunotherapy. Methods: Comprehensive immune profiling, including RNA-seq gene expression assessment of 395 immune genes, was performed on matched FFPE tumor samples from 22 stage I-III TNBC patients (14 patients treated with neoadjuvant chemotherapy alone (NAC) and 8 treated with neoadjuvant chemotherapy combined with pembrolizumab (NAC+I)). Results: Differential gene expression analysis revealed that in the NAC group, IL12B and IL13 were both significantly associated with pCR. In the NAC+I group, LCK and TP63 were significantly associated with pCR. Patients in both treatment groups exhibiting pCR tended to have greater tumor inflammation than non-pCR patients. In the NAC+I group, patients with pCR tended to have greater cell proliferation and higher PD-L1 expression, while in the NAC group, patients with pCR tended to have lower cancer testis antigen expression. Additionally, the NAC+I group trended toward a lower relative dose intensity averaged across all chemotherapy drugs, suggesting that more dose reductions or treatment delays occurred in the NAC+I group than the NAC group. Conclusions: A comprehensive understanding of immunologic factors could potentially predict pCR to chemotherapy alone, enabling the avoidance of the unnecessary treatment of these patients with checkpoint inhibitors.

Prognostic Value of "Basal-like" Morphology, Tumor-Infiltrating Lymphocytes and Multi-MAGE-A Expression in Triple-Negative Breast Cancer.

"Basal-like" (BL) morphology and the expression of cancer testis antigens (CTA) in breast cancer still have unclear prognostic significance. The aim of our research was to explore correlations of the morphological characteristics and tumor microenvironment in triple-negative breast carcinomas (TNBCs) with multi-MAGE-A CTA expression and to determine their prognostic significance. Clinical records of breast cancer patients who underwent surgery between January 2017 and December 2018 in four major Croatian clinical centers were analyzed. A total of 97 non-metastatic TNBCs with available tissue samples and treatment information were identified. Cancer tissue sections were additionally stained with programmed death-ligand 1 (PD-L1) Ventana (SP142) and multi-MAGE-A (mAb 57B). BL morphology was detected in 47 (49%) TNBCs and was associated with a higher Ki-67 proliferation index and histologic grade. Expression of multi-MAGE-A was observed in 77 (79%) TNBCs and was significantly associated with BL morphology. Lymphocyte-predominant breast cancer (LPBC) status was detected in 11 cases (11.3%) and significantly correlated with the Ki-67 proliferation index, increased number of intratumoral lymphocytes (itTIL), and PD-L1 expression. No impact of BL morphology, multi-MAGE-A expression, histologic type, or LPBC status on disease-free survival was observed. Our data suggest that tumor morphology could help identify patients with potential benefits from CTA-targeting immunotherapy.

The DNA Damage Response (DDR) landscape of endometrial cancer defines discrete disease subtypes and reveals therapeutic opportunities.

Genome maintenance is an enabling characteristic that allows neoplastic cells to tolerate the inherent stresses of tumorigenesis and evade therapy-induced genotoxicity. Neoplastic cells also deploy many mis-expressed germ cell proteins termed Cancer Testes Antigens (CTAs) to promote genome maintenance and survival. Here, we present the first comprehensive characterization of the DNA Damage Response (DDR) and CTA transcriptional landscapes of endometrial cancer in relation to conventional histological and molecular subtypes. We show endometrial serous carcinoma (ESC), an aggressive endometrial cancer subtype, is defined by gene expression signatures comprising members of the Replication Fork Protection Complex (RFPC) and Fanconi Anemia (FA) pathway and CTAs with mitotic functions. DDR and CTA-based profiling also defines a subset of highly aggressive endometrioid endometrial carcinomas (EEC) with poor clinical outcomes that share similar profiles to ESC yet have distinct characteristics based on conventional histological and genomic features. Using an unbiased CRISPR-based genetic screen and a candidate gene approach, we confirm that DDR and CTA genes that constitute the ESC and related EEC gene signatures are required for proliferation and therapy-resistance of cultured endometrial cancer cells. Our study validates the use of DDR and CTA-based tumor classifiers and reveals new vulnerabilities of aggressive endometrial cancer where none currently exist.

Abstract SY41-02: Experimental methods for high throughput discovery and validation of tumor antigens

Abstract The discovery and validation of tumor associated T-cell antigens, which can include neoantigens, viral antigens, cancer testis antigens, and others, is fundamental to the design of both cancer vaccines and engineered cell cancer immunotherapies. However, identifying tumor specific antigens that are highly presented within tumors, and identifying and validating T cell receptors (TCRs) that are specific to those antigens, remains a non-trivial exercise. Even identifying and validating a single antigen-specific T cell clonotype for advancement into a clinic trial remains a daunting task. In this talk, I will discuss a number of new experimental and computational tools that are designed to accelerate this process. The experimental toolsets include reagents and strategies that allow for the capture and analysis of T cells specific to hundreds to thousands of tumor-associated Class I and Class II antigens simultaneously, with as many as 100 patient bloods analyzed in a single experiment. Single cell analysis of the resulting data yields a deep characterization of the captured T cells, including T cell receptor α/β genes, antigen-MHC specificity, T cell phenotype, and donor identification. This type of analysis, in turn, provides large data bases that can fuel new computational strategies that can be harnessed (at a still early stage) to predict which TCRα/β genes associate with which putative antigen-MHCs, or to extract the biochemical and biophysical characteristics of TCR-antigen pairings that influence T cell phenotype. Thus, this presentation will span both new experimental and new computational toolsets. Citation Format: James R. Heath. Experimental methods for high throughput discovery and validation of tumor antigens [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr SY41-02.

Cancer testis antigen MAGEA3 in serum and serum-derived exosomes serves as a promising biomarker in lung adenocarcinoma

Cancer testis antigen (CTA) Melanoma Antigen Gene A3 (MAGEA3) were overexpressed in multiple tumor types, but the expression pattern of MAGEA3 in the serum of lung adenocarcinoma (LUAD) remains unclear. Clinically derived serum and serum exosome samples were used to assess the mRNA expression of MAGEA3 and MAGEA4 by qRT-PCR, and serum MAGEA3 and MAGEA4 protein expression were evaluated by ELISA in total 133 healthy volunteers’ and 289 LUAD patients’ serum samples. An analysis of the relationship of the mRNA and protein expression of MAGEA3 and MAGEA4 with clinicopathologic parameters was performed and the diagnostic value of MAGEA3 and MAGEA4 was plotted on an ROC curve. In addition, the correlation of MAGEA3 mRNA with infiltrating immune cells was investigated through TIMER, the CIBERSORT algorithm and the TISIDB database. Expression of serum and serum exosome MAGEA3 and MAGEA4 mRNA were significantly higher in LUAD patients than in healthy donors. MAGEA3 mRNA associated with tumor diameter, TMN stage, and NSE in LUAD serum samples, and MAGEA3 mRNA correlated with N stage in serum-derived exosomes, possessing areas under the curve (AUC) of 0.721 and 0.832, respectively. Besides, serum MAGEA3 protein levels were elevated in LUAD patients, and were closely related to stage and NSE levels, possessing AUC of 0.781. Further analysis signified that the expression of MAGEA3 mRNA was positive correlation with neutrophil, macrophages M2, dendritic cells resting, and eosinophilic, but negatively correlated with B cells, plasma cells, CD8 + T cells, CD4 + T cells, Th17 cells, macrophages and dendritic cells. Collectively, our results suggested that the MAGEA3 expression in mRNA and protein were upregulated in LUAD, and MAGEA3 could be used as a diagnostic biomarker and immunotherapy target for LUAD patients.