Effects of antineoplastic and immunomodulating agents on postvaccination SARS-CoV-2 breakthrough infections, antibody response, and serological cytokine profile.

BACKGROUND: Despite immunization, patients on antineoplastic and immunomodulating agents have a heightened risk of COVID-19 infection. However, accurately attributing this risk to specific medications remains challenging. METHODS: An observational cohort study from December 11, 2020 to September 22, 2022, within a large healthcare system in San Diego, California, USA was designed to identify medications associated with greatest risk of postimmunization SARS-CoV-2 infection. Adults prescribed WHO Anatomical Therapeutic Chemical (ATC) classified antineoplastic and immunomodulating medications were matched (by age, sex, race, and number of immunizations) with control patients not prescribed these medications yielding a population of 26 724 patients for analysis. From this population, 218 blood samples were collected from an enrolled subset to assess serological response and cytokine profile in relation to immunization. RESULTS: Prescription of WHO ATC classified antineoplastic and immunomodulatory agents was associated with elevated postimmunization SARS-CoV-2 infection risk (HR 1.50, 95% CI 1.38 to 1.63). While multiple immunization doses demonstrated a decreased association with postimmunization SARS-CoV-2 infection risk, antineoplastic and immunomodulatory treated patients with four doses remained at heightened risk (HR 1.23, 95% CI 1.06 to 1.43). Risk variation was identified among medication subclasses, with PD-1/PD-L1 inhibiting monoclonal antibodies, calcineurin inhibitors, and CD20 monoclonal antibody inhibitors identified to associate with increased risk of postimmunization SARS-CoV-2 infection. Antineoplastic and immunomodulatory treated patients also displayed a reduced IgG antibody response to SARS-CoV-2 epitopes alongside a unique serum cytokine profile. CONCLUSIONS: Antineoplastic and immunomodulating medications associate with an elevated risk of postimmunization SARS-CoV-2 infection in a drug-specific manner. This comprehensive, unbiased analysis of all WHO ATC classified antineoplastic and immunomodulating medications identifies medications associated with greatest risk. These findings are crucial in guiding and refining vaccination strategies for patients prescribed these treatments, ensuring optimized protection for this susceptible population in future COVID-19 variant surges and potentially for other RNA immunization targets.

NAIR: Network Analysis of Immune Repertoire.

T cells represent a crucial component of the adaptive immune system and mediate anti-tumoral immunity as well as protection against infections, including respiratory viruses such as SARS-CoV-2. Next-generation sequencing of the T-cell receptors (TCRs) can be used to profile the T-cell repertoire. We developed a customized pipeline for Network Analysis of Immune Repertoire (NAIR) with advanced statistical methods to characterize and investigate changes in the landscape of TCR sequences. We first performed network analysis on the TCR sequence data based on sequence similarity. We then quantified the repertoire network by network properties and correlated it with clinical outcomes of interest. In addition, we identified (1) disease-specific/associated clusters and (2) shared clusters across samples based on our customized search algorithms and assessed their relationship with clinical outcomes such as recovery from COVID-19 infection. Furthermore, to identify disease-specific TCRs, we introduced a new metric that incorporates the clonal generation probability and the clonal abundance by using the Bayes factor to filter out the false positives. TCR-seq data from COVID-19 subjects and healthy donors were used to illustrate that the proposed approach to analyzing the network architecture of the immune repertoire can reveal potential disease-specific TCRs responsible for the immune response to infection.

Do patients with metastatic pancreatic adenocarcinoma to the lung have improved survival?

INTRODUCTION: Pancreatic ductal adenocarcinoma (PDAC) is a genetically heterogeneous disease often diagnosed with synchronous metastatic disease involving the liver. Tumors with extra-abdominal spread that bypass the liver are thought to represent a unique molecular subgroup and those with isolated pulmonary metastatic disease are thought to have a more favorable clinical phenotype. METHOD: We conducted a retrospective review of patients with pathologically confirmed PDAC treated between the years 2007 and 2020 at a Scripps Health hospital. The final study sample (N = 205) included patients with isolated pulmonary metastasis (IL), isolated liver metastasis or synchronous liver and lung metastasis (LL), or metastasis to any site other than the liver or lung (NLL). Primary endpoint was overall survival (OS). Progression-free survival (PFS) and recurrence-free survival (RFS) were analyzed as secondary endpoints. Each survival outcome was analyzed using Cox proportional hazards tests. RESULTS: No statistically significant differences were seen between the three groups in OS, PFS, or RFS. Median OS for the IL group was 561 days, 341 days for the LL group, and 441 days for the NLL group. Median RFS was 748 days for the IL group, 574 days for the LL group, and 545 days for the NLL group. Median PFS was 307 for the IL group, 236 for the LL group, and 265 for the NLL group. When comparing only the IL and LL groups, a statistically significant difference in OS was seen favoring the IL group (HR1.59 LL vs IL [ref], CI 1.04-2.41, p = 0.031) CONCLUSION: Though statistically significant differences in survival outcomes were not seen in our population, there was a trend toward improved survival for patients with isolated lung metastases. When comparing only the IL to LL group, statistically significant overall survival favoring the IL group was seen. These findings highlight a potential prognostic indicator of metastatic PDAC.

A review of treatments targeting DNA-repair gene defects in metastatic castration resistant prostate cancer.

Prostate cancer is the most common cancer in men. About 6% of those diagnosed will develop metastatic disease. Unfortunately, metastatic prostate cancer is fatal. Prostate cancer can be castration sensitive or castration resistant. Many treatments have been shown to improve progression free survival and overall survival in metastatic castration resistant prostate cancer (mCRPC). In recent years, studies have been exploring targeting mutations in the DNA Damage Repair (DDR) response that may amplify oncogenes. In this paper, we aim to discuss DDR, new approved targeted therapies, and the most recent clinical trials in the setting of metastatic CRPC.

Novel Ensemble Feature Selection Approach and Application in Repertoire Sequencing Data.

The T and B cell repertoire make up the adaptive immune system and is mainly generated through somatic V(D)J gene recombination. Thus, the VJ gene usage may be a potential prognostic or predictive biomarker. However, analysis of the adaptive immune system is challenging due to the heterogeneity of the clonotypes that make up the repertoire. To address the heterogeneity of the T and B cell repertoire, we proposed a novel ensemble feature selection approach and customized statistical learning algorithm focusing on the VJ gene usage. We applied the proposed approach to T cell receptor sequences from recovered COVID-19 patients and healthy donors, as well as a group of lung cancer patients who received immunotherapy. Our approach identified distinct VJ genes used in the COVID-19 recovered patients comparing to the healthy donors and the VJ genes associated with the clinical response in the lung cancer patients. Simulation studies show that the ensemble feature selection approach outperformed other state-of-the-art feature selection methods based on both efficiency and accuracy. It consistently yielded higher stability and sensitivity with lower false discovery rates. When integrated with different classification methods, the ensemble feature selection approach had the best prediction accuracy. In conclusion, the proposed novel approach and the integration procedure is an effective feature selection technique to aid in correctly classifying different subtypes to better understand the signatures in the adaptive immune response associated with disease or the treatment in order to improve treatment strategies.

6 month serologic response to the Pfizer-BioNTech COVID-19 vaccine among healthcare workers.

AIM: Healthcare workers (HCWs) were among the first group of people vaccinated with the Pfizer-BioNTech Covid-19 vaccine (BNT162b2). Characterization of the kinetics of antibody response to vaccination is important to devise future vaccination strategies. To better characterize the antibody response to BNT162b2, we analyzed the kinetics of IgG and IgM antibody response to 5 different SARS-CoV-2 epitopes over a period of 6 months. METHODS AND RESULTS: An observational single-centered study was conducted to evaluate the temporal dynamics of anti-SARS-CoV-2 antibodies following immunization with two doses of BNT162b2. Anti-SARS-CoV-2 antibodies were assessed using the Maverick SARS-CoV-2 multi-antigen panel (Genalyte Inc.). Healthcare workers aged ≥18 receiving BNT162b2 vaccination who self-reported no prior symptoms of COVID-19 nor prior COVID-19 PCR test positivity, were included in this study. HCWs developed an IgG antibody response to SARS-CoV-2 Spike S1, Spike S1 receptor binding domain (RBD), Spike S1S2 and Spike S2 after vaccination. IgG response was observed at two weeks following immunization in most participant samples and continued to increase at week 4, but subsequently decreased significantly starting at 3 months and up to 6 months. In contrast, IgM response to respective epitopes was minimal. CONCLUSION: Multiplex results demonstrate that, contrary to natural infection, immunization with BNT162b2 produces minimal anti-Spike IgM response. Polyclonal IgG response to Spike declined at 3 months and continued to do so up to 6 months.

Hospitalization requiring intensive care unit due to SARS-CoV-2 infection correlated with IgM depression and IgG elevation.

AIM: This study investigated the humoral response against SARS-CoV-2 in patients needing intensive care unit (ICU) care compared with those on general medicine wards. MATERIALS & METHODS: The authors retrospectively reviewed 113 hospitalized patients with COVID-19. They assessed antibody response against five SARS-CoV-2 epitopes at 6-14 days post symptom onset in these patients. RESULTS: Patients with ICU admissions had decreased anti-nucleocapsid immunoglobulin (Ig)M and increased anti-spike IgG compared with patients not requiring the ICU. IgG levels were positively correlated with length of stay. CONCLUSION: Higher levels of IgG against the spike protein correlate with COVID-19 disease severity and length of stay in hospitalized patients. This adds to the knowledge of biochemical response to clinical disease and may help predict ICU needs.

An observational study of hospitalized COVID-19 patients with cancer in San Diego county.

Aim: To delineate clinical correlates of COVID-19 infection severity in hospitalized patients with malignancy. Methods: The authors conducted a retrospective review of all hospitalized patients with a hematologic and/or solid tumor malignancy presenting to the authors' institution between 1 March 2020 and 5 January 2021, with a laboratory confirmed diagnosis of COVID-19. Univariate and multivariate logistic regression analyses were used to determine associations between specific severity outcomes and clinical characteristics. Results: Among 2771 hospitalized patients with COVID-19, 246 (8.88%) met inclusion criteria. Patients who were actively receiving treatment had an increased rate of death following admission (odds ratio [OR]: 2.7). After adjusting for significant covariates, the odds ratio increased to 4.4. Patients with cancer involvement of the lungs had a trend toward increased odds of death after adjusting for covariates (OR: 2.3). Conclusions: Among COVID-19 positive hospitalized cancer patients, systemic anti-cancer therapy was associated with significantly increased odds of mortality.

Plain language summary Though cancer is a biologically heterogenous disease with a wide spectrum of clinical features and behavior, accumulating evidence suggests that cancer patients are at greater susceptibility to COVID-19 infection and more likely to experience morbidity and mortality from COVID-19 infection than non-cancer patients. In this study, the authors reviewed the clinical characteristics of patients with a diagnosis of cancer hospitalized with COVID-19 to assess potential correlates of COVID-19 severity in this population. Notably, analysis of the hospital data revealed a statistically significant increased incidence of mortality in cancer patients who were receiving systemic anti-cancer treatment, including chemotherapy, immunotherapy or targeted therapy, than in those not on therapy. Likewise, there was a trend toward increased mortality in those with either primary or metastatic tumor involvement of the lung compared with those without lung involvement.

Malignant Melanoma With Neuroendocrine Differentiation: A Case Report and Literature Review.

BACKGROUND: Melanoma has a wide range of histologic variants and cytomorphologic features that make its diagnosis challenging. Melanoma can also rarely have neuroendocrine markers adding further diagnostic uncertainty particularly given that unrelated tumor types, such as prostate cancer, can also display focal neuroendocrine differentiations. CASE PRESENTATION: Our patient is a 74-year-old Caucasian man found to have a lung mass. Initial biopsy revealed typical microscopic morphology and neuroendocrine differentiation consistent with small cell carcinoma. Despite standard chemoradiation treatment, the patient continued to progress with new metastasis in the brain, liver and bone. Subsequent chest wall biopsy revealed golden-brown pigment associated with melanin. Further tumor immunohistochemistry revealed extensive neuroendocrine differentiation with CD56, synaptophysin, and INSM1, as well as strong immunoreactivity for melanocyte markers including SOX10, S100, PRAME, and MITF, consistent with metastatic melanoma with neuroendocrine differentiation. Genomic testing revealed increased tumor mutational burden and alterations in NF1, BRAF, CDKN2A/B, TERT. The patient was transitioned to checkpoint inhibitor therapy with nivolumab and ipilimumab and had resolution of his intracranial mass and decrease in size of other metastatic lesions. CONCLUSION: Often the combination of anatomic findings such as a lung mass, typical microscopic morphology, and confirmation of neuroendocrine differentiation correctly identifies a patient with small cell carcinoma. However, in a patient who fails to respond to treatment, a broader immunohistochemical workup along with molecular testing with additional tissue may be warranted.

Targeting the PI3K-AKT-mTOR Pathway in Castration Resistant Prostate Cancer: A Review Article.

BACKGROUND: Prostate cancer is one of leading causes of cancer death among men worldwide. Androgen deprivation therapy is a central part of the prostate cancer treatment algorithm, however, resistance to androgen deprivation commonly leads to disease progression. Mutations in the phosphoinositide-3-kinase pathway (PI3K) have been implicated in cancer progression and the development of castration-resistance. Thus, inhibitors of this pathway and its downstream signaling partners have been studied as potential therapeutic agents to treat metastatic castration resistant prostate cancer (mCRPC).  In this article, we review recent clinical results for novel targeted therapies against the PI3K-AKT-mTOR pathway. MATERIALS AND METHODS: Trials included in this systemic review were identified through conference abstracts, citations in review articles, PubMed, and ClinicalTrials.gov. Trial eligibility was independent of clinical setting or sample size. RESULTS: A total of 13 prospective clinical trials between 2012 and 2020 were reviewed: Two trials for pan-PI3K inhibitors, 2 trials for selective PI3K inhibitors, 4 trials for AKT inhibitors, 5 trials for mTOR inhibitors, and 1 for a combined PI3K and mTOR inhibitor. All studies were phase I or II studies with primary outcomes of either safety and tolerability or efficacy. CONCLUSION: Overall, pan-PI3K inhibitors and selective-PI3K inhibitors have not demonstrated clinical efficacy and may have significant adverse effects. AKT inhibitors may have significant adverse effects, but showed some evidence of improved survival. mTORC1 inhibitors show modest efficacy and significant adverse effects.

Durvalumab-induced myocarditis, myositis, and myasthenia gravis: a case report.

BACKGROUND: Immune checkpoint inhibitors are effective therapies for a wide range of malignancies. Their increased use has led to a wide range of immune-related adverse effects including skin, gastrointestinal, pulmonary, endocrine, cardiac, and neurologic complications. CASE PRESENTATION: We present the case of a 72-year-old Caucasian man with non-small cell lung cancer who was admitted for dyspnea after two cycles of durvalumab. He was found to have significantly elevated levels of serum creatinine kinase and troponin with a negative cardiac catheterization. During his hospitalization, he developed progressive dyspnea and new-onset axial weakness, ultimately leading to the diagnosis of durvalumab-induced myocarditis, myasthenia gravis, and myositis. CONCLUSION: This is, to our knowledge, the first reported case of anti-programmed cell death ligand 1-induced combination of myocarditis, myasthenia gravis, and myositis. While the use of immunologic agents has resulted in overall improved cancer outcomes, their increased use has led to a vast spectrum of immune-related adverse effects. We review the diagnostic workup and management of patients with these immune-related adverse effects, underscoring the importance of early identification given the potential for rapid deterioration.

Cross-platform comparison of immune-related gene expression to assess intratumor immune responses following cancer immunotherapy.

Neoadjuvant immunotherapy can induce immune responses within the tumor microenvironment. Gene expression can be used to assess responses with limited amounts of conventionally-fixed patient-derived samples. We aim to assess the cross-platform concordance of immune-related gene expression data. We performed comparisons across three panels in two platforms: Nanostring nCounter® PanCancer Immune Profiling Panel (nS), HTG EdgeSeq Oncology Biomarker Panel (HTG OBP) and Precision Immuno-Oncology Panel (HTG PIP). All tissue samples of 14 neoadjuvant GM-CSF treated, 14 neoadjuvant Provenge treated, and 12 untreated prostate cancer patients were radical prostatectomy (RP) tissues, while 6 prostatitis patients and 6 non-prostatitis subjects were biopsies. For all 52 patients, more than 90% of the common genes were significantly correlated (p < 0.05) and more than 76% of the common genes were highly correlated (r > 0.5) between any two panels. Co-inertia analysis also demonstrated high overall dataset structure similarity (correlation>0.84). Although both dimensionality reduction visualization analysis and unsupervised hierarchical cluster analysis for highly correlated common genes (r > 0.9) suggested a high-level of consistency across the panels, there were subsets of genes that were differentially expressed across the panels. In addition, while the effect size of the differential testing for neoadjuvant treated vs. untreated localized prostate cancer patients across the panels were significantly correlated, some genes were only differentially expressed in the HTG panels. Finally, the HTG PIP panel had the best classification performance among the 3 panels. These differences detected may be a result of the different panels or platforms due to their technical setting and focus. Thus, researchers should be aware of those potential differences when deciding which platform and panel to use.

Long-term Sculpting of the B-cell Repertoire following Cancer Immunotherapy in Patients Treated with Sipuleucel-T.

Sipuleucel-T is an autologous cellular immunotherapy, administered as three infusions, for metastatic castration-resistant prostate cancer (mCRPC). Sipuleucel-T induces T- and B-cell responses to prostatic acid phosphatase (PAP), correlating to improved survival. The long-term impact of sipuleucel-T on tumor antigen-specific immunologic memory remains unknown, in particular, B-cell responses, as measured by antigen-specific antibody responses and B-cell receptor (BCR) sequences. To evaluate whether sipuleucel-T could induce long-term immunologic memory, we examined circulating B-cell responses before and after sipuleucel-T treatment in two groups of patients with mCRPC: those who had previously received sipuleucel-T (treated; median, 8.9 years since the previous treatment) versus those who had not (naïve). Before re-treatment, previously treated patients exhibited persistent antibody responses as well as more focused and convergent BCR repertoires with distinct V(D)J gene usage compared with naïve patients. After re-treatment, previously treated patients maintained high-frequency clones and developed more convergent BCRs at earlier time points unlike naïve patients. With the first sipuleucel-T infusion specifically, previously treated patients had less shuffling within the 100 most abundant baseline clones. In contrast, naïve patients exhibited great BCR turnover with a continued influx of new B-cell clones. Social network analysis showed that previously treated patients had more highly organized B-cell repertoires, consistent with greater clonal maturation. Higher treatment-induced BCR clonality correlated with longer survival for naïve patients. These results demonstrated the capacity of sipuleucel-T to induce long-term immune memory and lasting changes to the B-cell repertoire.

Combination immunotherapy induces distinct T-cell repertoire responses when administered to patients with different malignancies.

BACKGROUND: CTLA-4 blockade with ipilimumab is Food and Drug Administration-approved for melanoma as a monotherapy and has been shown to modulate the circulating T-cell repertoire. We have previously reported clinical trials combining CTLA-4 blockade with granulocyte-macrophage colony-stimulating factor (GM-CSF) in metastatic melanoma patients and in metastatic castration resistant prostate cancer (mCRPC) patients. Here, we investigate the effect that cancer type has on circulating T cells in metastatic melanoma and mCRPC patients, treated with ipilimumab and GM-CSF. METHODS: We used next-generation sequencing of T-cell receptors (TCR) to compare the circulating T cells of melanoma and mCRPC patients receiving the same treatment with ipilimumab and GM-CSF by Wilcoxon rank sum test. Flow cytometry was utilized to investigate specific T-cell populations. TCR sequencing results were correlated with each T-cell subpopulation by Spearman's rank correlation coefficient. Of note, 14 metastatic melanoma patients had samples available for TCR sequencing and 21 had samples available for flow cytometry analysis; 37 mCRPC patients had samples available for sequencing of whom 22 have TCR data available at both timepoints; 20 of these patients had samples available for flow cytometry analysis and 16 had data available at both timepoints. RESULTS: While melanoma and mCRPC patients had similar pretreatment circulating T-cell counts, treatment induces greater expansion of circulating T cells in melanoma patients. Metastatic melanoma patients have a higher proportion of clones that increased more than fourfold after the treatment compared with mCRPC patients (18.9% vs 11.0%, p=0.017). Additionally, melanoma patients compared with mCRPC patients had a higher ratio of convergent frequency (1.22 vs 0.60, p=0.012). Decreases in clonality induced by treatment are associated with baseline CD8+ T-cell counts in both patient groups, but are more pronounced in the melanoma patients (r=-0.81, p<0.001 vs r=-0.59, p=0.02). TRIAL REGISTRATION NUMBERS: NCT00064129; NCT01363206.

3D: diversity, dynamics, differential testing - a proposed pipeline for analysis of next-generation sequencing T cell repertoire data.

BACKGROUND: Cancer immunotherapy has demonstrated significant clinical activity in different cancers. T cells represent a crucial component of the adaptive immune system and are thought to mediate anti-tumoral immunity. Antigen-specific recognition by T cells is via the T cell receptor (TCR) which is unique for each T cell. Next generation sequencing (NGS) of the TCRs can be used as a platform to profile the T cell repertoire. Though there are a number of software tools available for processing repertoire data by mapping antigen receptor segments to sequencing reads and assembling the clonotypes, most of them are not designed to track and examine the dynamic nature of the TCR repertoire across multiple time points or between different biologic compartments (e.g., blood and tissue samples) in a clinical context. RESULTS: We integrated different diversity measures to assess the T cell repertoire diversity and examined the robustness of the diversity indices. Among those tested, Clonality was identified for its robustness as a key metric for study design and the first choice to measure TCR repertoire diversity. To evaluate the dynamic nature of T cell clonotypes across time, we utilized several binary similarity measures (such as Baroni-Urbani and Buser overlap index), relative clonality and Morisita's overlap index, as well as the intraclass correlation coefficient, and performed fold change analysis, which was further extended to investigate the transition of clonotypes among different biological compartments. Furthermore, the application of differential testing enabled the detection of clonotypes which were significantly changed across time. By applying the proposed "3D" analysis pipeline to the real example of prostate cancer subjects who received sipuleucel-T, an FDA-approved immunotherapy, we were able to detect changes in TCR sequence frequency and diversity thus demonstrating that sipuleucel-T treatment affected TCR repertoire in blood and in prostate tissue. We also found that the increase in common TCR sequences between tissue and blood after sipuleucel-T treatment supported the hypothesis that treatment-induced T cell migrated into the prostate tissue. In addition, a second example of prostate cancer subjects treated with Ipilimumab and granulocyte macrophage colony stimulating factor (GM-CSF) was presented in the supplementary documents to further illustrate assessing the treatment-associated change in a clinical context by the proposed workflow. CONCLUSIONS: Our paper provides guidance to study the diversity and dynamics of NGS-based TCR repertoire profiling in a clinical context to ensure consistency and reproducibility of post-analysis. This analysis pipeline will provide an initial workflow for TCR sequencing data with serial time points and for comparing T cells in multiple compartments for a clinical study.

Immune Toxicities Elicted by CTLA-4 Blockade in Cancer Patients Are Associated with Early Diversification of the T-cell Repertoire.

While immune checkpoint blockade elicits efficacious responses in many patients with cancer, it also produces a diverse and unpredictable number of immune-related adverse events (IRAE). Mechanisms driving IRAEs are generally unknown. Because CTLA-4 blockade leads to proliferation of circulating T cells, we examined in this study whether ipilimumab treatment leads to clonal expansion of tissue-reactive T cells. Rather than narrowing the T-cell repertoire to a limited number of clones, ipilimumab induced greater diversification in the T-cell repertoire in IRAE patients compared with patients without IRAEs. Specifically, ipilimumab triggered increases in the numbers of clonotypes, including newly detected clones and a decline in overall T-cell clonality. Initial broadening in the repertoire occurred within 2 weeks of treatment, preceding IRAE onset. IRAE patients exhibited greater diversity of CD4+ and CD8+ T cells, but showed no differences in regulatory T-cell numbers relative to patients without IRAEs. Prostate-specific antigen responses to ipilimumab were also associated with increased T-cell diversity. Our results show how rapid diversification in the immune repertoire immediately after checkpoint blockade can be both detrimental and beneficial for patients with cancer. Cancer Res; 77(6); 1322-30. ©2016 AACR.

Clonotypic Diversification of Intratumoral T Cells Following Sipuleucel-T Treatment in Prostate Cancer Subjects.

Sipuleucel-T is an autologous cellular therapy for asymptomatic, or minimally symptomatic, metastatic castrate-resistant prostate cancer, designed to stimulate an immune response against prostate cancer. In a recent clinical trial (NCT00715104), we found that neoadjuvant sipuleucel-T increased the number of activated T cells within the tumor microenvironment. The current analysis examined whether sipuleucel-T altered adaptive T-cell responses by expanding pre-existing T cells or by recruiting new T cells to prostate tissue. Next-generation sequencing of the T-cell receptor (TCR) genes from blood or prostate tissue was used to quantitate and track T-cell clonotypes in these treated subjects with prostate cancer. At baseline, there was a significantly greater diversity of circulating TCR sequences in subjects with prostate cancer compared with healthy donors. Among healthy donors, circulating TCR sequence diversity remained unchanged over the same time interval. In contrast, sipuleucel-T treatment reduced circulating TCR sequence diversity versus baseline as measured by the Shannon index. Interestingly, sipuleucel-T treatment resulted in greater TCR sequence diversity in resected prostate tissue in sipuleucel-T-treated subjects versus tissue of nonsipuleucel-T-treated subjects with prostate cancer. Furthermore, sipuleucel-T increased TCR sequence commonality between blood and resected prostate tissue in treated versus untreated subjects with prostate cancer. The broadening of the TCR repertoire within the prostate tissue supports the hypothesis that sipuleucel-T treatment facilitates the recruitment of T cells into the prostate. Our results highlight the importance of assessing T-cell response to immunotherapy both in the periphery and in tumor tissue. Cancer Res; 76(13); 3711-8. ©2016 AACR.