Immunomodulatory effects and improved outcomes with cisplatin- versus carboplatin-based chemotherapy plus atezolizumab in urothelial cancer

In metastatic urothelial cancer (mUC), cisplatin versus carboplatin leads to durable disease control in a subset of patients. The IMvigor130 trial reveals more favorable effects with atezolizumab combined with gemcitabine and cisplatin (GemCis) versus gemcitabine and carboplatin (GemCarbo). This study investigates the immunomodulatory effects of cisplatin as a potential explanation for these observations. Our findings indicate that improved outcomes with GemCis versus GemCarbo are primarily observed in patients with pretreatment tumors exhibiting features of restrained adaptive immunity. In addition, GemCis versus GemCarbo ± atezolizumab induces transcriptional changes in circulating immune cells, including upregulation of antigen presentation and T cell activation programs. In vitro experiments demonstrate that cisplatin, compared with carboplatin, exerts direct immunomodulatory effects on cancer cells, promoting dendritic cell activation and antigen-specific T cell killing. These results underscore the key role of immune modulation in cisplatin's efficacy in mUC and highlight the importance of specific chemotherapy backbones in immunotherapy combination regimens.

Atezolizumab plus Magrolimab, Niraparib, or Tocilizumab versus Atezolizumab Monotherapy in Platinum-Refractory Metastatic Urothelial Carcinoma: A Phase Ib/II Open-Label, Multicenter, Randomized Umbrella Study (MORPHEUS Urothelial Carcinoma)

PURPOSE

The MORPHEUS platform was designed to identify early efficacy signals and evaluate the safety of novel immunotherapy combinations across cancer types. The phase Ib/II MORPHEUS-UC trial (NCT03869190) is evaluating atezolizumab plus magrolimab, niraparib, or tocilizumab in platinum-refractory locally advanced or metastatic urothelial carcinoma (mUC). Additional treatment combinations were evaluated and will be reported separately.

PATIENTS AND METHODS

Patients had locally advanced or mUC that progressed during or following treatment with a platinum-containing regimen. The primary efficacy endpoint was investigator-assessed objective response rate (ORR). Key secondary endpoints included investigator-assessed progression-free survival (PFS) and overall survival (OS). Safety and exploratory biomarker analyses were also conducted.

RESULTS

Seventy-six patients were randomized to receive either atezolizumab plus magrolimab (n = 16), atezolizumab plus niraparib (n = 15), atezolizumab plus tocilizumab (n = 15), or atezolizumab monotherapy (control; n = 30). No additive benefit in ORR, PFS, or OS was seen in the treatment arms versus the control. The best confirmed ORR was 26.7% with atezolizumab plus magrolimab, 6.7% with atezolizumab plus niraparib, 20.0% with atezolizumab plus tocilizumab, and 27.6% with atezolizumab monotherapy. Overall, the treatment combinations were tolerable, and adverse events were consistent with each agent's known safety profile. Trends were observed for shrinkage of programmed death-ligand 1-positive tumors (atezolizumab, atezolizumab plus magrolimab, atezolizumab plus tocilizumab), inflamed tumors, or tumors with high mutational burden (atezolizumab), and immune excluded tumors (atezolizumab plus magrolimab).

CONCLUSIONS

The evaluated regimens in MORPHEUS-UC were tolerable. However, response rates for the combinations did not meet the criteria for further development in platinum-experienced locally advanced or mUC.

A Phase 1b/2 Study of Atezolizumab with or Without Bacille Calmette-Guérin in Patients with High-risk Non-muscle-invasive Bladder Cancer

BACKGROUND

Bacille Calmette-Guérin (BCG) is the standard therapy after transurethral resection of bladder tumour for high-risk non-muscle-invasive bladder cancer (NMIBC). However, post-BCG recurrence/progression occurs frequently, and noncystectomy options are limited.

OBJECTIVE

To evaluate the safety and clinical activity of atezolizumab ± BCG in high-risk BCG-unresponsive NMIBC.

DESIGN, SETTING, AND PARTICIPANTS

This phase 1b/2 GU-123 study (NCT02792192) treated patients with BCG-unresponsive NMIBC who had carcinoma in situ with atezolizumab ± BCG.

INTERVENTION

Patients in cohorts 1A and 1B received atezolizumab 1200 mg IV q3w for ≤96 wk. Those in cohort 1B also received standard BCG induction (six weekly doses) and maintenance courses (three doses weekly starting at month 3) with optional maintenance at 6, 12, 18, 24, and 30 mo.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Coprimary endpoints were safety and 6-mo complete response (CR) rate. Secondary endpoints included 3-mo CR rate and duration of CR; 95% confidence intervals were calculated using the Clopper-Pearson method.

RESULTS AND LIMITATIONS

At data cut-off (September 29, 2020), 24 patients were enrolled (cohort 1A, n = 12; cohort 1B, n = 12), and the recommended BCG dose was 50 mg in cohort 1B. Four patients (33%) had adverse events (AEs) leading to BCG dose modification/interruption. Three patients (25%) in cohort 1A reported atezolizumab-related grade 3 AEs; cohort 1B had no atezolizumab- or BCG-related grade ≥3 AEs. No grade 4/5 AEs were reported. The 6-mo CR rate was 33% in cohort 1A (median duration of CR, 6.8 mo) and 42% in cohort 1B (median duration of CR, not reached [≥12 mo]). These results are limited by the small sample size of GU-123.

CONCLUSIONS

In this first report of the atezolizumab-BCG combination in NMIBC, atezolizumab ± BCG was well tolerated, with no new safety signals or treatment-related deaths. Preliminary results suggested clinically meaningful activity; the combination favoured a longer duration of response.

PATIENT SUMMARY

We studied atezolizumab with and without bacille Calmette-Guérin (BCG) to determine whether this combination was safe and had clinical activity in patients with high-risk noninvasive bladder cancer (high-grade bladder tumours that affect the outermost lining of the bladder wall) that has previously been treated with BCG and is still present or occurred again. Our results suggest that atezolizumab with or without BCG was generally safe and could be used to treat patients unresponsive to BCG.

CD8+ T cell-intrinsic IL-6 signaling promotes resistance to anti-PD-L1 immunotherapy

Although immune checkpoint inhibitors (ICIs) are established as effective cancer therapies, overcoming therapeutic resistance remains a critical challenge. Here we identify interleukin 6 (IL-6) as a correlate of poor response to atezolizumab (anti-PD-L1) in large clinical trials of advanced kidney, breast, and bladder cancers. In pre-clinical models, combined blockade of PD-L1 and the IL-6 receptor (IL6R) causes synergistic regression of large established tumors and substantially improves anti-tumor CD8⁺ cytotoxic T lymphocyte (CTL) responses compared with anti-PD-L1 alone. Circulating CTLs from cancer patients with high plasma IL-6 display a repressed functional profile based on single-cell RNA sequencing, and IL-6-STAT3 signaling inhibits classical cytotoxic differentiation of CTLs in vitro. In tumor-bearing mice, CTL-specific IL6R deficiency is sufficient to improve anti-PD-L1 activity. Thus, based on both clinical and experimental evidence, agents targeting IL-6 signaling are plausible partners for combination with ICIs in cancer patients.

First-In-Human Phase I Study of the OX40 Agonist MOXR0916 in Patients with Advanced Solid Tumors

PURPOSE

OX40, a receptor transiently expressed by T cells upon antigen recognition, is associated with costimulation of effector T cells and impairment of regulatory T-cell function. This first-in-human study evaluated MOXR0916, a humanized effector-competent agonist IgG1 monoclonal anti-OX40 antibody.

PATIENTS AND METHODS

Eligible patients with locally advanced or metastatic refractory solid tumors were treated with MOXR0916 intravenously once every 3 weeks (Q3W). A 3+3 dose-escalation stage (0.2-1,200 mg; n = 34) was followed by expansion cohorts at 300 mg (n = 138) for patients with melanoma, renal cell carcinoma, non-small cell lung carcinoma, urothelial carcinoma, and triple-negative breast cancer.

RESULTS

MOXR0916 was well tolerated with no dose-limiting toxicities observed. An MTD was not reached. Most patients (95%) experienced at least one adverse event (AE); 56% of AEs, mostly grade 1-2, were related to MOXR0916. Most common treatment-related AEs included fatigue (17%), diarrhea (8%), myalgia (7%), nausea (6%), decreased appetite (6%), and infusion-related reaction (5%). Pharmacokinetic (PK) parameters were dose proportional between 80 and 1,200 mg and supported Q3W administration. The recommended expansion dose based on PK and OX40 receptor saturation was 300 mg Q3W. Immune activation and upregulation of PD-L1 was observed in a subset of paired tumor biopsies. One renal cell carcinoma patient experienced a confirmed partial response. Overall, 33% of patients achieved stable disease.

CONCLUSIONS

Although objective responses were rarely observed with MOXR0916 monotherapy, the favorable safety profile and evidence of tumor immune activation in a subset of patients support further investigation in combination with complementary agents such as PD-1/PD-L1 antagonists.

Single-cell analysis reveals clonally expanded tumor-associated CD57+ CD8 T cells are enriched in the periphery of patients with metastatic urothelial cancer responding to PD-L1 blockade

BACKGROUND

A growing body of evidence suggests that T-cell responses against neoantigens are critical regulators of response to immune checkpoint blockade. We previously showed that circulating neoantigen-specific CD8 T cells in patients with lung cancer responding to anti-Programmed death-ligand 1 (PD-L1) (atezolizumab) exhibit a unique phenotype with high expression of CD57, CD244, and KLRG1. Here, we extended our analysis on neoantigen-specific CD8 T cells to patients with metastatic urothelial cancer (mUC) and further profiled total CD8 T cells to identify blood-based predictive biomarkers of response to atezolizumab.

METHODS

We identified tumor neoantigens from 20 patients with mUC and profiled their peripheral CD8 T cells using highly multiplexed combinatorial tetramer staining. Another set of patients with mUC treated with atezolizumab (n=30) or chemotherapy (n=40) were selected to profile peripheral CD8 T cells by mass cytometry. Using single-cell transcriptional analysis (single-cell RNA sequencing (scRNA-seq)), together with CITE-seq (cellular indexing of transcriptomes and epitopes by sequencing) and paired T-cell receptor (TCR) sequencing, we further characterized peripheral CD8 T cells in a subset of patients (n=16).

RESULTS

High frequency of CD57 was observed in neoantigen-specific CD8 T cells in patients with mUC responding to atezolizumab. Extending these findings to bulk CD8 T cells, we found higher frequency of CD57 expressing CD8 T cells before treatment in patients responding to atezolizumab (n=20, p<0.01) but not to chemotherapy. These findings were corroborated in a validation cohort (n=30, p<0.01) and notably were independent of known biomarkers of response. scRNA-seq analysis identified a clonally expanded cluster enriched within CD57⁺ CD8 T cells in responding patients characterized by higher expression of genes associated with activation, cytotoxicity, and tissue-resident memory markers. Furthermore, compared with CD57^- CD8 T cells, TCRs of CD57⁺ CD8 T cells showed increased overlap with the TCR repertoire of tumor-infiltrating T cells.

CONCLUSIONS

Collectively, we show high frequencies of CD57 among neoantigen-specific and bulk CD8 T cells in patients responding to atezolizumab. The TCR repertoire overlap between peripheral CD57⁺ CD8 T cells and tumor-infiltrating lymphocytes suggest that accumulation of peripheral CD57⁺ CD8 T cells is reflective of an ongoing antitumor T-cell response. Our findings provide evidence and rationale for using circulating CD8 T cells expressing CD57 as a readily accessible blood-based biomarker for selecting patients with mUC for atezolizumab therapy.

Abstract 6226: Single-cell analysis reveals clonally expanded CD57+ CD8 T cells in periphery are associated with response to PD-L1 blockade in bladder cancer patients

The recent success of immune checkpoint blockade has revolutionized cancer treatment for many cancers, however, only a fraction of patients with advanced stages of cancers experience clinical benefit. Many studies have suggested that T cells against tumor neoantigens are critical mediators of response to checkpoint blockade. We showed previously that neoantigen-specific CD8 T cells in cancer patients responding to anti-PD-L1 (atezolizumab) therapy express high levels of CD57 and KLRG1. Here, we extended the study to bladder cancer patients treated with atezolizumab to identify predictive biomarkers of response. We immune profiled circulating CD8 T cells using multidimensional mass cytometry and single cell sequencing, and compared patients with objective response and progressive disease.

We found a higher frequency of CD57-expressing CD8 T cells at baseline in responding patients compared to patients who progressed during therapy (n=20, p&lt;0.01). High expression of CD57 was also observed in neoantigen-specific CD8 T cells in responding patients. These findings were corroborated in a validation cohort (n=30, p&lt;0.01) and notably, higher frequency of CD57+ T cells was only observed in patients responding to atezolizumab and not in patients responding to chemotherapy treatment (n=40). We further used single-cell transcriptomics, together with CITE-seq and paired TCR sequencing, to characterize CD57+ CD8 T cells in a subset of patients (n=16) and identified a cluster within CD57+ CD8 T cells, which was characterized by enrichment of genes associated with activation, cytotoxicity and tissue resident memory markers in responding patients. Compared to patients with progressive disease, there was an increased clonal expansion among CD57+ CD8 T cells at baseline in responders, which was driven specifically by the activated cluster. Furthermore, we found increased overlap between TCR repertoires of tumor-infiltrating T cells and CD57+CD8 T cells, compared to CD57- CD8 T cells in the periphery, suggesting that levels of CD57+ CD8 T cells in the periphery could be indicative of quality of anti-tumor T cell response.This study identified and confirmed that elevated levels of circulating CD8 T cells expressing CD57 are associated with response to atezolizumab in bladder cancer patients. These data provide evidence and rationale for an easily accessible blood-based biomarker for selecting patients for atezolizumab therapy.

Citation Format: Mahesh Yadav, Michael Fehlings, Leesun Kim, Xiangnan Guan, Kobe C. Yuen, Alireza Tafazzol, Deepali Rishipathak, Shomyesh Sanjabi, Andrew Wallace, Alessandra Nardin, Siming Ma, Ana Milojkovic, Evan Newell, Sanjeev Mariathasan. Single-cell analysis reveals clonally expanded CD57+ CD8 T cells in periphery are associated with response to PD-L1 blockade in bladder cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6226.

Atezolizumab (atezo) with or without Bacille Calmette-Guérin (BCG) in patients (pts) with high-risk nonmuscle-invasive bladder cancer (NMIBC): Results from a phase Ib/II study

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Background: Standard treatment (tx) for high-risk NMIBC is transurethral resection of bladder tumor (TURBT) followed by BCG induction and maintenance. However, ≈50% of pts experience recurrence and/or progression after tx and may be ineligible for or refuse cystectomy. The PD-L1/PD-1 pathway may be involved with immune escape in NMIBC following BCG exposure. Here, we report results of atezo (anti–PD-L1) ± BCG in BCG-unresponsive, high-risk NMIBC. Methods: This multicenter study (NCT02792192) enrolled pts with BCG-unresponsive NMIBC with carcinoma in situ who had repeat TURBT. Cohort 1A and 1B pts received atezo 1200 mg IV q3w for ≤96 wk. Cohort 1B pts also received standard BCG induction (qw × 6 doses) and maintenance (qw × 3 doses at 3 mo), with optional maintenance courses at 6, 12, 18, 24, and 30 mo. For cohort 1B only, de-escalation was allowed for ≤3 BCG dose levels (full dose 50 mg, 66% and 33% of full dose). Co-primary outcomes were safety and complete response (CR) rate at 6 mo (6-mo bladder biopsy required). Duration of CR and 3-mo CR rate (key secondary outcomes) and 12-mo CR rate (exploratory) were also shown. Results: Cohorts 1A and 1B enrolled 12 pts each. Median age was 74 y; most pts had ECOG PS 0 (n = 7 [58%] in each cohort). At data cutoff (Sep 29, 2020), median atezo tx duration was 22.7 wk in cohort 1A and 31.6 wk in 1B. Following dose de-escalation in cohort 1B, the recommended BCG dose was 50 mg. BCG dose modification/interruption occurred in 4 pts (33%) due to an AE. The most common reason for tx discontinuation was disease recurrence or progression in both cohorts. Three pts (25%) in cohort 1A had atezo-related Gr 3 AEs (most common: maculopapular rash, n = 2); no atezo- or BCG-related Gr ≥3 AEs were seen in cohort 1B. Three dose-limiting toxicities occurred (1 [8%] in cohort 1A and 2 [17%] in cohort 1B), all reported as AEs of special interest. No Gr 4/5 AEs were reported. CRs, which appeared durable, were seen in both cohorts (Table). Conclusions: In this first report of atezo + BCG in NMIBC, atezo as mono- and combination therapy was well tolerated, with no new safety signals or tx-related deaths. Preliminary data suggested clinically meaningful activity, especially with atezo + BCG, requiring confirmation in a larger setting. Clinical trial information: NCT02792192. [Table: see text]

Abstract 2000: Systemic and tumor associated IL-8 correlates with resistance to PD-L1 blockade

Elevated plasma interleukin-8 (IL-8) is a poor prognostic factor for many cancers. However, the association of IL-8 with clinical outcomes to checkpoint inhibition has not been comprehensively evaluated in randomized studies. Moreover, the source of IL-8 and the underlying biology that influences resistance to immune checkpoint inhibitors remain unknown. Here we analyzed circulating IL-8 protein in plasma, and IL8 gene expression in peripheral blood mononuclear cells (PBMC) and tumors of patients treated with atezolizumab (anti-PD-L1 mAb), from multiple randomized trials in metastatic urothelial carcinoma (mUC) and metastatic renal cell carcinoma (mRCC). High levels of IL-8 in plasma, PBMCs and tumors, were associated with decreased efficacy in mUC and mRCC patients treated with atezolizumab, even in tumors that were classically CD8+ T cell inflamed. mUC patients treated with atezolizumab, but not with chemotherapy, who experienced an on-treatment decrease in plasma IL-8, exhibited improved overall survival. IL-8 is primarily expressed in circulating and intratumoral myeloid cells, and high IL8 expression was associated with the downregulation of the antigen presentation machinery in myeloid cells. A better understanding of IL-8-mediated myeloid inflammation in curtailing responses to checkpoint inhibitors is essential for developing new therapies for patients.

Citation Format: Kobe Yuen, Lifen Liu, Congfen Li, Deepali Rishipathak, Patrick Williams, Edward Kadel, Hartmut Koeppen, Shravan Madireddi, Shilpa Keerthivasan, Ying-Jun Chen, Zora Modrusen, Romain Banchereau, Ning Leng, Priti Hegde, Mahrukh Huseni, Sanjeev Mariathasan. Systemic and tumor associated IL-8 correlates with resistance to PD-L1 blockade [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2000.

High systemic and tumor-associated IL-8 correlates with reduced clinical benefit of PD-L1 blockade

Although elevated plasma interleukin-8 (pIL-8) has been associated with poor outcome to immune checkpoint blockade ¹, this has not been comprehensively evaluated in large randomized studies. Here we analyzed circulating pIL-8 and IL8 gene expression in peripheral blood mononuclear cells and tumors of patients treated with atezolizumab (anti-PD-L1 monoclonal antibody) from multiple randomized trials representing 1,445 patients with metastatic urothelial carcinoma (mUC) and metastatic renal cell carcinoma. High levels of IL-8 in plasma, peripheral blood mononuclear cells and tumors were associated with decreased efficacy of atezolizumab in patients with mUC and metastatic renal cell carcinoma, even in tumors that were classically CD8⁺ T cell inflamed. Low baseline pIL-8 in patients with mUC was associated with increased response to atezolizumab and chemotherapy. Patients with mUC who experienced on-treatment decreases in pIL-8 exhibited improved overall survival when treated with atezolizumab but not with chemotherapy. Single-cell RNA sequencing of the immune compartment showed that IL8 is primarily expressed in circulating and intratumoral myeloid cells and that high IL8 expression is associated with downregulation of the antigen-presentation machinery. Therapies that can reverse the impacts of IL-8-mediated myeloid inflammation will be essential for improving outcomes of patients treated with immune checkpoint inhibitors.

Abstract 2676: Associations of peripheral biomarkers to outcomes to anti-PD-L1 immune checkpoint blockade in metastatic urothelial cancer

Introduction Immune checkpoint blockade such as inhibition of programmed death-1 (PD-1) or programmed death-ligand 1 (PD-L1) has been shown to be effective in metastatic urothelial cancer (mUC) and many other types of cancers. Despite its robust efficacy, a large proportion of patients still fail to show durable responses; therefore, it is important to understand the mechanisms that drive clinical responses, as well as the pathways associated with lack of response. Circulating peripheral biomarkers are particularly useful as readily accessible and minimally invasive markers to enable monitoring both tumor growth and responses to treatment.

Methods Baseline plasma from 337 patients treated with an anti-PD-L1 (atezolizumab) in the mUC Ph2 trial IMvigor210 (NCT02108652) were analyzed using a Myriad-RBM panel. To further characterize the findings, single-cell RNA sequencing (scRNAseq) was performed with PBMC isolated from responders and non-responders (n=5 each) to atezolizumab in the same trial. NanoString gene expression levels of the PBMC isolated from mUC patients in IMvigor210 was used to validate the identified signatures.

Results High levels of CXCL9 (HR: 0.692, CI: 0.529-0.903, p=0.006) and leptin (HR: 0.633, CI: 0.485-0.825, p=0.001) were associated with better overall survival (OS), whereas high levels of pro-inflammatory cytokines IL6 (HR: 2.744, CI: 2.084-3.612, p&lt;0.0001) and CXCL8/IL8 (HR: 2.639, CI: 1.997-3.489, p=0.006) were associated with poor OS. In addition, high levels of angiogenesis and cell adhesion proteins such as TIMP1 (HR: 2.317, CI: 1.773-3.029, p&lt;0.0001), VWF (HR: 1.571, CI: 1.207-2.045, p=0.001), and ICAM1 (HR: 1.349, CI: 1.034-1.76, p=0.026) correlated with poor OS. High plasma IL6 levels and high tumor IL6 expression are significantly enriched in non-responders in the T cell excluded phenotype, further suggesting association of IL6 with stroma/angiogenesis. Results from scRNAseq show response (CR/PR) to checkpoint blockade was associated with adaptive immune signature (GZMM, PSMB8, PSMB9) (FDR&lt;0.0001) in lymphoid PBMC. Lack of response (SD/PD) was associated with complement coagulation (PF4, THBS, TIMP1) (FDR&lt;0.0001) and innate inflammation (IL8, IL1B, IL18) (FDR=&lt;0.0001) signatures in the myeloid cells. We confirmed these outcome-associated signatures with OS modeling with gene expression levels in PBMC.

Conclusion Peripheral biomarker analysis revealed that adaptive immune signatures to be associated better clinical outcome, whereas innate inflammation and angiogenesis signatures to be correlated with worse clinical outcome to anti-PD-L1 immunotherapy. The link between IL6 and angiogenesis in the tumor microenvironment will be further characterized. Understanding the genes and pathways associated with outcomes will shed light on peripheral biomarker development.

Citation Format: Kobe C. Yuen, Vinita Gupta, Congfen Li, Deepali Rishipathak, Edward E. Kadel, Ying-Jiun J. Chen, Leonard D. Goldstein, Zora Modrusan, Sanjeev Mariathasan. Associations of peripheral biomarkers to outcomes to anti-PD-L1 immune checkpoint blockade in metastatic urothelial cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2676.

Differential increase in the expression of heat shock protein family members during sleep deprivation and during sleep

Although sleep is thought to be restorative from prior wakeful activities, it is not clear what is being restored. To determine whether the synthesis of macromolecules is increased in the cerebral cortex during sleep, we subjected C57BL/6 mice to 6 hours of sleep deprivation and then screened the expression of 1176 genes of known function by using cDNA arrays. The expression of the heat shock proteins (HSP), endoplasmic reticulum protein (ERp72) and glucose-regulated protein (GRp78), was among the genes whose expression was significantly elevated in the cortex during sleep deprivation, whereas GRp78 and GRp94 mRNAs were elevated in the cortex during recovery sleep after sleep deprivation, as confirmed by conventional and quantitative real-time polymerase chain reaction and/or Northern analyses. A systematic evaluation of the expression of six heat shock protein family members (ERP72, GRp78, GRp94, HSP27, HSP70-1, and HSP84) in seven brain regions revealed increased mRNA levels in cortex, basal forebrain, hypothalamus, cerebellum and medulla during sleep deprivation, whereas increased mRNA levels during recovery sleep were limited to the cortex and medulla. Immunohistochemical studies identified increased numbers of GRp78-, GRp94-, and ERp72-immunoreactive cells in the dorsal and lateral cortex during sleep deprivation but, during recovery sleep, elevated numbers of these cells were found only in the lateral cortex. In the medulla, increased numbers of GRp94-immunoreactive cells were observed in nucleus tractus solitarius, dorsal motor nucleus of the vagus and the rostroventrolateral medulla during recovery sleep. The widespread increase of heat shock protein family mRNAs in brain during sleep deprivation may be a neuroprotective response to prolonged wakefulness. In contrast, the relatively limited heat shock protein family mRNA expression during recovery sleep may be related to the role of heat shock proteins in protein biogenesis and thus to the restorative function of sleep.