ATF3 characterizes aggressive drug-tolerant persister cells in HGSOC.

High-grade serous ovarian cancer (HGSOC) represents the most common and lethal subtype of ovarian cancer. Despite initial response to platinum-based standard therapy, patients commonly suffer from relapse that likely originates from drug-tolerant persister (DTP) cells. We generated isogenic clones of treatment-naïve and cisplatin-tolerant persister HGSOC cells. In addition, single-cell RNA sequencing of barcoded cells was performed in a xenograft model with HGSOC cell lines after platinum-based therapy. Published single-cell RNA-sequencing data from neo-adjuvant and non-treated HGSOC patients and patient data from TCGA were analyzed. DTP-derived cells exhibited morphological alterations and upregulation of epithelial-mesenchymal transition (EMT) markers. An aggressive subpopulation of DTP-derived cells showed high expression of the stress marker ATF3. Knockdown of ATF3 enhanced the sensitivity of aggressive DTP-derived cells to cisplatin-induced cell death, implying a role for ATF3 stress response in promoting a drug tolerant persister cell state. Furthermore, single cell lineage tracing to detect transcriptional changes in a HGSOC cell line-derived xenograft relapse model showed that cells derived from relapsed solid tumors express increased levels of EMT and multiple endoplasmic reticulum (ER) stress markers, including ATF3. Single cell RNA sequencing of epithelial cells from four HGSOC patients also identified a small cell population resembling DTP cells in all samples. Moreover, analysis of TCGA data from 259 HGSOC patients revealed a significant progression-free survival advantage for patients with low expression of the ATF3-associated partial EMT genes. These findings suggest that increased ATF3 expression together with partial EMT promote the development of aggressive DTP, and thereby relapse in HGSOC patients.

Perfusion Air Culture of Precision-Cut Tumor Slices: An Ex Vivo System to Evaluate Individual Drug Response under Controlled Culture Conditions.

Precision-cut tumor slices (PCTS) maintain tissue heterogeneity concerning different cell types and preserve the tumor microenvironment (TME). Typically, PCTS are cultured statically on a filter support at an air-liquid interface, which gives rise to intra-slice gradients during culture. To overcome this problem, we developed a perfusion air culture (PAC) system that can provide a continuous and controlled oxygen medium, and drug supply. This makes it an adaptable ex vivo system for evaluating drug responses in a tissue-specific microenvironment. PCTS from mouse xenografts (MCF-7, H1437) and primary human ovarian tumors (primary OV) cultured in the PAC system maintained the morphology, proliferation, and TME for more than 7 days, and no intra-slice gradients were observed. Cultured PCTS were analyzed for DNA damage, apoptosis, and transcriptional biomarkers for the cellular stress response. For the primary OV slices, cisplatin treatment induced a diverse increase in the cleavage of caspase-3 and PD-L1 expression, indicating a heterogeneous response to drug treatment between patients. Immune cells were preserved throughout the culturing period, indicating that immune therapy can be analyzed. The novel PAC system is suitable for assessing individual drug responses and can thus be used as a preclinical model to predict in vivo therapy responses.

Breast cancer plasticity is restricted by a LATS1-NCOR1 repressive axis.

Breast cancer, the most frequent cancer in women, is generally classified into several distinct histological and molecular subtypes. However, single-cell technologies have revealed remarkable cellular and functional heterogeneity across subtypes and even within individual breast tumors. Much of this heterogeneity is attributable to dynamic alterations in the epigenetic landscape of the cancer cells, which promote phenotypic plasticity. Such plasticity, including transition from luminal to basal-like cell identity, can promote disease aggressiveness. We now report that the tumor suppressor LATS1, whose expression is often downregulated in human breast cancer, helps maintain luminal breast cancer cell identity by reducing the chromatin accessibility of genes that are characteristic of a "basal-like" state, preventing their spurious activation. This is achieved via interaction of LATS1 with the NCOR1 nuclear corepressor and recruitment of HDAC1, driving histone H3K27 deacetylation near NCOR1-repressed "basal-like" genes. Consequently, decreased expression of LATS1 elevates the expression of such genes and facilitates slippage towards a more basal-like phenotypic identity. We propose that by enforcing rigorous silencing of repressed genes, the LATS1-NCOR1 axis maintains luminal cell identity and restricts breast cancer progression.

The BCL-2 inhibitor ABT-199/venetoclax synergizes with proteasome inhibition via transactivation of the MCL-1 antagonist NOXA.

Enhanced expression of anti-apoptotic B-cell lymphoma 2 (BCL-2) protein is frequent in cancer. Targeting of BCL-2 with the specific inhibitor ABT-199 (Venetoclax) has significant clinical activity in malignant diseases such as chronic lymphocytic leukemia and multiple myeloma. The small molecule drug ABT-199 mimics the pro-apoptotic BCL-2 homology domain 3 of BH3-only proteins and blocks the hydrophobic BC-groove in BCL-2. We have previously shown that ABT-199 synergizes with the proteasome inhibitor (PI) bortezomib in soft tissue sarcoma derived cells and cell lines to induce apoptosis. Synergistic apoptosis induction relies on the pore-forming effector BAX and expression of the pro-apoptotic BH3-only protein NOXA. Bortezomib augments expression of NOXA by blocking its proteasomal degradation. Interestingly, shown here for the first time, expression of NOXA is strongly enhanced by ABT-199 induced integrated stress response (ISR). ISR transcription factors ATF3 & ATF4 mediate transactivation of the BH3-only protein NOXA which specifically inhibits the anti-apoptotic MCL-1. Thus, NOXA potentiates the efficacy of the BCL-2 inhibitor ABT-199 by simultaneous inhibition of MCL-1. Hence, ABT-199 has a double impact by directly blocking anti-apoptotic BCL-2 and inhibiting MCL-1 via transactivated NOXA. By preventing degradation of NOXA PIs synergize with ABT-199. Synergism of ABT-199 and PIs therefore occurs on several, previously unexpected levels. This finding should prompt clinical evaluation of combinatorial regimens in further malignancies.

Immunopeptidomics-Guided Warehouse Design for Peptide-Based Immunotherapy in Chronic Lymphocytic Leukemia.

Antigen-specific immunotherapies, in particular peptide vaccines, depend on the recognition of naturally presented antigens derived from mutated and unmutated gene products on human leukocyte antigens, and represent a promising low-side-effect concept for cancer treatment. So far, the broad application of peptide vaccines in cancer patients is hampered by challenges of time- and cost-intensive personalized vaccine design, and the lack of neoepitopes from tumor-specific mutations, especially in low-mutational burden malignancies. In this study, we developed an immunopeptidome-guided workflow for the design of tumor-associated off-the-shelf peptide warehouses for broadly applicable personalized therapeutics. Comparative mass spectrometry-based immunopeptidome analyses of primary chronic lymphocytic leukemia (CLL) samples, as representative example of low-mutational burden tumor entities, and a dataset of benign tissue samples enabled the identification of high-frequent non-mutated CLL-associated antigens. These antigens were further shown to be recognized by pre-existing and de novo induced T cells in CLL patients and healthy volunteers, and were evaluated as pre-manufactured warehouse for the construction of personalized multi-peptide vaccines in a first clinical trial for CLL (NCT04688385). This workflow for the design of peptide warehouses is easily transferable to other tumor entities and can provide the foundation for the development of broad personalized T cell-based immunotherapy approaches.

Comprehensive Genomic and Transcriptomic Analysis for Guiding Therapeutic Decisions in Patients with Rare Cancers.

The clinical relevance of comprehensive molecular analysis in rare cancers is not established. We analyzed the molecular profiles and clinical outcomes of 1,310 patients (rare cancers, 75.5%) enrolled in a prospective observational study by the German Cancer Consortium that applies whole-genome/exome and RNA sequencing to inform the care of adults with incurable cancers. On the basis of 472 single and six composite biomarkers, a cross-institutional molecular tumor board provided evidence-based management recommendations, including diagnostic reevaluation, genetic counseling, and experimental treatment, in 88% of cases. Recommended therapies were administered in 362 of 1,138 patients (31.8%) and resulted in significantly improved overall response and disease control rates (23.9% and 55.3%) compared with previous therapies, translating into a progression-free survival ratio >1.3 in 35.7% of patients. These data demonstrate the benefit of molecular stratification in rare cancers and represent a resource that may promote clinical trial access and drug approvals in this underserved patient population. SIGNIFICANCE: Rare cancers are difficult to treat; in particular, molecular pathogenesis-oriented medical therapies are often lacking. This study shows that whole-genome/exome and RNA sequencing enables molecularly informed treatments that lead to clinical benefit in a substantial proportion of patients with advanced rare cancers and paves the way for future clinical trials.See related commentary by Eggermont et al., p. 2677.This article is highlighted in the In This Issue feature, p. 2659.

Characteristics and outcome of patients with low-/intermediate-risk acute promyelocytic leukemia treated with arsenic trioxide: an international collaborative study.

The aim of this study was to characterize a large series of 154 patients with acute promyelocytic leukemia (median age, 53 years; range, 18-90 years) and evaluate real-life outcome after up-front treatment with arsenic trioxide and all-trans retinoic acid. All patients were included in the prospective NAPOLEON registry (NCT02192619) between 2013 and 2019. The acute promyelocytic leukemia was de novo in 91% (n=140) and therapy-related in 9% (n=14); 13% (n=20) of the patients were older than 70 years. At diagnosis bleeding/hemorrhage was present in 38% and thrombosis in 3%. Complete remission was achieved in 152 patients (99%), whereas two patients (1%) experienced induction death within 18 days after starting therapy. With a median follow-up of 1.99 years (95% confidence interval: 1.61-2.30 years) 1-year and 2-year overall survival rates were 97% (95% confidence interval: 94-100%) and 95% (95% confidence interval: 91-99%), respectively. Age above 70 years was associated with a significantly shorter overall survival (P<0.001) compared to that of younger patients. So far no relapses have been observed. Six patients (4%) died in complete remission at a median of 0.95 years after diagnosis (range, 0.18-2.38 years). Our data confirm the efficiency and durability of arsenic trioxide and all-trans retinoic acid therapy in the primary management of adults with low-/intermediate-risk acute promyelocytic leukemia in the real-life setting, irrespective of age.

PET-guided eBEACOPP treatment of advanced-stage Hodgkin lymphoma (HD18): follow-up analysis of an international, open-label, randomised, phase 3 trial.

BACKGROUND: The German Hodgkin Study Group's HD18 trial established the safety and efficacy of PET-guided eBEACOPP (bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone in escalated doses) for the treatment of advanced-stage Hodgkin lymphoma. However, because of a protocol amendment during the enrolment period (June 1, 2011) that changed standard treatment from eight to six cycles, the results of the HD18 trial have been partially immature. We report a prespecified 5-year follow-up analysis of the completed HD18 trial. METHODS: HD18 was an international, open-label, randomised, phase 3 trial done in 301 hospitals and private practices in five European countries. Patients aged 18-60 years with newly diagnosed, advanced-stage Hodgkin lymphoma and an Eastern Cooperative Oncology Group performance status of 0-2 were recruited. After receiving an initial two cycles of eBEACOPP (1250 mg/m2 intravenous cyclophosphamide [day 1], 35 mg/m2 intravenous doxorubicin [day 1], 200 mg/m2 intravenous etoposide [day 1-3], 100 mg/m2 oral procarbazine [day 1-7], 40 mg/m2 oral prednisone [day 1-14], 1·4 mg/m2 intravenous vincristine [day 8], and 10 mg/m2 intravenous bleomycin [day 8]), patients underwent a contrast-enhanced CT and PET scan (PET-2). Patients with positive PET-2 were randomly assigned to receive standard therapy (an additional six cycles of eBEACOPP; ie, eight cycles in total) or experimental therapy (an additional six cycles of eBEACOPP plus 375 mg/m2 intravenous rituximab; ie, eight cycles in total) until June 1, 2011. After June 1, 2011, all patients with positive PET-2 were assigned to the updated standard therapy with an additional four cycles of eBEACOPP (ie, six cycles in total). Patients with negative PET-2 were randomly assigned (1:1) to receive standard therapy (an additional six cycles of eBEACOPP [ie, eight cycles in total] until June 1, 2011; an additional four cycles of eBEACOPP [ie, six cycles in total] after June 1, 2011) or experimental therapy (an additional two cycles of eBEACOPP; ie, four cycles in total). Randomisation was done centrally with the minimisation method, including a random component, stratified by centre, age, stage, international prognostic score, and sex. The primary endpoint was progression-free survival. HD18 aimed to improve 5-year progression-free survival by 15% in the PET-2-positive intention-to-treat cohort and to exclude inferiority of 6% or more in 5-year progression-free survival in the PET-2-negative per-protocol population. This study is registered with ClinicalTrials.gov, NCT00515554, and is completed. FINDINGS: Between May 14, 2008, and July 18, 2014, 2101 patients were enrolled and 1945 were assigned to a treatment group according to their PET-2 result. In the PET-2-positive cohort, with a median follow-up of 73 months (IQR 59 to 94), 5-year progression-free survival was 89·9% (95% CI 85·7 to 94·1) in 217 patients assigned to eight cycles of eBEACOPP before the protocol amendment and 87·7% (83·1 to 92·4) in 217 patients assigned to eight cycles of rituximab plus eBEACOPP (p=0·40). Among 506 patients who received six cycles of eBEACOPP after the protocol amendment, 5-year progression-free survival was 90·1% (95% CI 87·2 to 92·9), with a median follow-up of 58 months (IQR 39 to 66). In the PET-2-negative cohort, with a median follow-up of 66 months (IQR 54 to 85) in the combined pre-amendment and post-amendment groups, 5-year progression-free survival was 91·2% (95% CI 88·4 to 93·9) in 446 patients who received eight or six cycles of eBEACOPP and 93·0% (90·6 to 95·4) in 474 patients who received four cycles of eBEACOPP (difference 1·9% [95% CI -1·8 to 5·5]). In the subgroup of PET-2-negative patients randomly assigned after protocol amendment, 5-year progression-free survival was 90·9% (95% CI 86·8 to 95·1) in 202 patients assigned to receive six cycles of eBEACOPP and 91·0% (86·6 to 95·5) in 200 patients assigned to receive four cycles of eBEACOPP (difference 0·1% [-5·9 to 6·2]). INTERPRETATION: Long-term follow-up confirms the efficacy and safety of PET-2-guided eBEACOPP in patients with advanced-stage Hodgkin lymphoma. The reduction from eight to four cycles of eBEACOPP represents a benchmark in the treatment of early-responding patients, who can now be potentially cured with a short and safe treatment approach. FUNDING: Deutsche Krebshilfe, Swiss State Secretariat for Education, Research and Innovation SERI (Switzerland), and Roche Pharma. TRANSLATION: For the German translation of the abstract see Supplementary Materials section.

Sorafenib or placebo in patients with newly diagnosed acute myeloid leukaemia: long-term follow-up of the randomized controlled SORAML trial.

Early results of the randomized placebo-controlled SORAML trial showed that, in patients with newly diagnosed acute myeloid leukaemia (AML), sorafenib led to a significant improvement in event-free (EFS) and relapse-free survival (RFS). In order to describe second-line treatments and their implications on overall survival (OS), we performed a study after a median follow-up time of 78 months. Newly diagnosed fit AML patients aged ≤60 years received sorafenib (n = 134) or placebo (n = 133) in addition to standard chemotherapy and as maintenance treatment. The 5-year EFS was 41 versus 27% (HR 0.68; p = 0.011) and 5-year RFS was 53 versus 36% (HR 0.64; p = 0.035). Allogeneic stem cell transplantation (allo SCT) was performed in 88% of the relapsed patients. Four years after salvage allo SCT, the cumulative incidence of relapse was 54 versus 35%, and OS was 32 versus 50%. The 5-year OS from randomization in all study patients was 61 versus 53% (HR 0.82; p = 0.282). In conclusion, the addition of sorafenib to chemotherapy led to a significant prolongation of EFS and RFS. Although the OS benefit did not reach statistical significance, these results confirm the antileukaemic activity of sorafenib.

The BCL-2 selective inhibitor ABT-199 sensitizes soft tissue sarcomas to proteasome inhibition by a concerted mechanism requiring BAX and NOXA.

Soft tissue sarcomas (STS) are a heterogeneous group of malignancies predominantly affecting children and young adults. Despite improvements in multimodal therapies, 5-year survival rates are only 50% and new treatment options in STS are urgently needed. To develop a rational combination therapy for the treatment of STS we focused on ABT-199 (Venetoclax), a BCL-2 specific BH3-mimetic, in combination with the proteasome inhibitor bortezomib (BZB). Simultaneous inhibition of BCL-2 and the proteasome resulted in strongly synergistic apoptosis induction. Mechanistically, ABT-199 mainly affected the multidomain effector BAX by liberating it from BCL-2 inhibition. The combination with BZB additionally resulted in the accumulation of BOK, a BAX/BAK homologue, and of the BH3-only protein NOXA, which inhibits the anti-apoptotic protein MCL-1. Thus, the combination of ABT-199 and BZB sensitizes STS cells to apoptosis by simultaneously releasing several defined apoptotic restraints. This synergistic mechanism of action was verified by CRISPR/Cas9 knock-out, showing that both BAX and NOXA are crucial for ABT-199/BZB-induced apoptosis. Noteworthy, efficient induction of apoptosis by ABT-199/BZB was not affected by the p53 status and invariably detected in cell lines and patient-derived tumor cells of several sarcoma types, including rhabdomyo-, leiomyo-, lipo-, chondro-, osteo-, or synovial sarcomas. Hence, we propose the combination of ABT-199 and BZB as a promising strategy for the treatment of STS, which should warrant further clinical investigation.

Direct impact of cisplatin on mitochondria induces ROS production that dictates cell fate of ovarian cancer cells.

Patients with high-grade serous ovarian cancer (HGSC) frequently receive platinum-based chemotherapeutics, such as cisplatin. Cisplatin binds to DNA and induces DNA-damage culminating in mitochondria-mediated apoptosis. Interestingly, mitochondrial DNA is critically affected by cisplatin but its relevance in cell death induction is scarcely investigated. We find that cisplatin sensitive HGSC cell lines contain higher mitochondrial content and higher levels of mitochondrial ROS (mtROS) than cells resistant to cisplatin induced cell death. In clonal sub-lines from OVCAR-3 mitochondrial content and basal oxygen consumption rate correlate with sensitivity to cisplatin induced apoptosis. Mitochondria are in two ways pivotal for cisplatin sensitivity because not only knock-down of BAX and BAK but also the ROS scavenger glutathione diminish cisplatin induced apoptosis. Mitochondrial ROS correlates with mitochondrial content and reduction of mitochondrial biogenesis by knock-down of transcription factors PGC1α or TFAM attenuates both mtROS induction and cisplatin induced apoptosis. Increasing mitochondrial ROS by inhibition or knock-down of the ROS-protective uncoupling protein UCP2 enhances cisplatin induced apoptosis. Similarly, enhancing ROS by high-dose ascorbic acid or H2O2 augments cisplatin induced apoptosis. In summary, mitochondrial content and the resulting mitochondrial capacity to produce ROS critically determine HGSC cell sensitivity to cisplatin induced apoptosis. In line with this observation, data from the human protein atlas (www.proteinatlas.org) indicates that high expression of mitochondrial marker proteins (TFAM and TIMM23) is a favorable prognostic factor in ovarian cancer patients. Thus, we propose mitochondrial content as a biomarker for the response to platinum-based therapies. Functionally, this might be exploited by increasing mitochondrial content or mitochondrial ROS production to enhance sensitivity to cisplatin based anti-cancer therapies.

Notch1 signaling in NOTCH1-mutated mantle cell lymphoma depends on Delta-Like ligand 4 and is a potential target for specific antibody therapy.

BACKGROUND: NOTCH1 gene mutations in mantle cell lymphoma (MCL) have been described in about 5-10% of cases and are associated with significantly shorter survival rates. The present study aimed to investigate the biological impact of this mutation in MCL and its potential as a therapeutic target. METHODS: Activation of Notch1 signaling upon ligand-stimulation and inhibitory effects of the monoclonal anti-Notch1 antibody OMP-52M51 in NOTCH1-mutated and -unmutated MCL cells were assessed by Western Blot and gene expression profiling. Effects of OMP-52M51 treatment on tumor cell migration and tumor angiogenesis were evaluated with chemotaxis and HUVEC tube formation assays. The expression of Delta-like ligand 4 (DLL4) in MCL lymph nodes was analyzed by immunofluorescence staining and confocal microscopy. A MCL mouse model was used to assess the activity of OMP-52M51 in vivo. RESULTS: Notch1 expression can be effectively stimulated in NOTCH1-mutated Mino cells by DLL4, whereas in the NOTCH1-unmutated cell line JeKo-1, less effect was observed upon any ligand-stimulation. DLL4 was expressed by histiocytes in both, NOTCH1-mutated and -unmutated MCL lymph nodes. Treatment of NOTCH1-mutated MCL cells with the monoclonal anti-Notch1 antibody OMP-52M51 effectively prevented DLL4-dependent activation of Notch1 and suppressed the induction of numerous direct Notch target genes involved in lymphoid biology, lymphomagenesis and disease progression. Importantly, in lymph nodes from primary MCL cases with NOTCH1/2 mutations, we detected an upregulation of the same gene sets as observed in DLL4-stimulated Mino cells. Furthermore, DLL4 stimulation of NOTCH1-mutated Mino cells enhanced tumor cell migration and angiogenesis, which could be abolished by treatment with OMP-52M51. Importantly, the effects observed were specific for NOTCH1-mutated cells as they did not occur in the NOTCH1-wt cell line JeKo-1. Finally, we confirmed the potential activity of OMP-52M51 to inhibit DLL4-induced Notch1-Signaling in vivo in a xenograft mouse model of MCL. CONCLUSION: DLL4 effectively stimulates Notch1 signaling in NOTCH1-mutated MCL and is expressed by the microenvironment in MCL lymph nodes. Our results indicate that specific inhibition of the Notch1-ligand-receptor interaction might provide a therapeutic alternative for a subset of MCL patients.

Phase I study of domatinostat (4SC-202), a class I histone deacetylase inhibitor in patients with advanced hematological malignancies.

OBJECTIVES: Domatinostat (4SC-202) is a selective class I histone deacetylase inhibitor (HDACi). This phase I study investigated safety, tolerability, pharmacokinetics (PK), pharmacodynamics, and antitumor activity in patients with advanced hematological malignancies. METHODS: Domatinostat was administered orally once (QD) or twice daily (BID) on days 1-14 with 7 days off or continuously days 1-21 in a 3 + 3 design at 7 dose levels from 25 to 400 mg total daily dose (TDD). Twenty-four patients were treated with domatinostat. RESULTS: No formal maximum tolerated dose (MTD) was determined. One dose-limiting toxicity (DLT, grade 4 hypercalcemia) occurred during 200 mg BID continuous treatment. Six patients were reported with ≥ grade 3 treatment-related adverse events (TRAE; grade 3 hematological in three patients, grade 3 and grade 4 liver enzyme increase in 2 patients, grade 4 pulmonary embolism, and grade 4 hypercalcemia in one patient each). Higher grade hepatic TRAE occurred in the 200 mg BID continuous treatment cohort. Out of 24 patients, 1 achieved a complete response, 1 achieved a partial response, and 18 had stable disease as best response. CONCLUSION: Administration of domatinostat was safe, well tolerated with signs of antitumor activity. Four hundred milligram TDD in a 200 mg BID schedule (14 + 7) is the recommended phase II dose for monotherapy.

Cyclin D1-CDK4 activity drives sensitivity to bortezomib in mantle cell lymphoma by blocking autophagy-mediated proteolysis of NOXA.

BACKGROUND: Mantle cell lymphoma (MCL) is an aggressive B-non-Hodgkin lymphoma with generally poor outcome. MCL is characterized by an aberrantly high cyclin D1-driven CDK4 activity. New molecular targeted therapies such as inhibitors of the ubiquitin-proteasome system (UPS) have shown promising results in preclinical studies and MCL patients. Our previous research revealed stabilization of the short-lived pro-apoptotic NOXA as a critical determinant for sensitivity to these inhibitors. It is currently unclear how cyclin D1 overexpression and aberrant CDK4 activity affect NOXA stabilization and treatment efficacy of UPS inhibitors in MCL. METHODS: The effect of cyclin D1-driven CDK4 activity on response of MCL cell lines and primary cells to proteasome inhibitor treatment was investigated using survival assays (Flow cytometry, AnnexinV/PI) and Western blot analysis of NOXA protein. Half-life of NOXA protein was determined by cycloheximide treatment and subsequent Western blot analysis. The role of autophagy was analyzed by LC3-II protein expression and autophagolysosome detection. Furthermore, silencing of autophagy-related genes was performed using siRNA and MCL cells were treated with autophagy inhibitors in combination with proteasome and CDK4 inhibition. RESULTS: In this study, we show that proteasome inhibitor-mediated cell death in MCL depends on cyclin D1-driven CDK4 activity. Inhibition of cyclin D1/CDK4 activity significantly reduced proteasome inhibitor-mediated stabilization of NOXA protein, mainly driven by an autophagy-mediated proteolysis. Bortezomib-induced cell death was significantly potentiated by compounds that interfere with autophagosomal function. Combined treatment with bortezomib and autophagy inhibitors enhanced NOXA stability leading to super-induction of NOXA protein. In addition to established autophagy modulators, we identified the fatty acid synthase inhibitor orlistat to be an efficient autophagy inhibitor when used in combination with bortezomib. Accordingly, this combination synergistically induced apoptosis both in MCL cell lines and in patient samples. CONCLUSION: Our data demonstrate that CDK4 activity in MCL is critical for NOXA stabilization upon treatment with UPS inhibitors allowing preferential induction of cell death in cyclin D transformed cells. Under UPS blocked conditions, autophagy appears as the critical regulator of NOXA induction. Therefore, inhibitors of autophagy are promising candidates to increase the activity of proteasome inhibitors in MCL.

Altered p53 functionality in cancer-associated fibroblasts contributes to their cancer-supporting features.

Within the tumor microenvironment, cancer cells coexist with noncancerous adjacent cells that constitute the tumor microenvironment and impact tumor growth through diverse mechanisms. In particular, cancer-associated fibroblasts (CAFs) promote tumor progression in multiple ways. Earlier studies have revealed that in normal fibroblasts (NFs), p53 plays a cell nonautonomous tumor-suppressive role to restrict tumor growth. We now wished to investigate the role of p53 in CAFs. Remarkably, we found that the transcriptional program supported by p53 is altered substantially in CAFs relative to NFs. In agreement, the p53-dependent secretome is also altered in CAFs. This transcriptional rewiring renders p53 a significant contributor to the distinct intrinsic features of CAFs, as well as promotes tumor cell migration and invasion in culture. Concordantly, the ability of CAFs to promote tumor growth in mice is greatly compromised by depletion of their endogenous p53. Furthermore, cocultivation of NFs with cancer cells renders their p53-dependent transcriptome partially more similar to that of CAFs. Our findings raise the intriguing possibility that tumor progression may entail a nonmutational conversion ("education") of stromal p53, from tumor suppressive to tumor supportive.

PET-guided treatment in patients with advanced-stage Hodgkin's lymphoma (HD18): final results of an open-label, international, randomised phase 3 trial by the German Hodgkin Study Group.

BACKGROUND: The intensive polychemotherapy regimen eBEACOPP (bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone in escalated doses) is very active in patients with advanced-stage Hodgkin's lymphoma, albeit at the expense of severe toxicities. Individual patients might be cured with less burdensome therapy. We investigated whether metabolic response determined by PET after two cycles of standard regimen eBEACOPP (PET-2) would allow adaption of treatment intensity, increasing it for PET-2-positive patients and reducing it for PET-2-negative patients. METHODS: In this open-label, randomised, parallel-group phase 3 trial, we recruited patients aged 18-60 years with newly diagnosed, advanced-stage Hodgkin's lymphoma in 301 hospitals and private practices in Germany, Switzerland, Austria, the Netherlands, and the Czech Republic. After central review of PET-2, patients were assigned (1:1) to one of two parallel treatment groups on the basis of their PET-2 result. Patients with positive PET-2 were randomised to receive six additional cycles of either standard eBEACOPP (8 × eBEACOPP in total) or eBEACOPP with rituximab (8 × R-eBEACOPP). Those with negative PET-2 were randomised between standard treatment with six additional cycles of eBEACOPP (8 × eBEACOPP) or experimental treatment with two additional cycles (4 × eBEACOPP). A protocol amendment in June, 2011, introduced a reduction of standard therapy to 6 × eBEACOPP; after this point, patients with positive PET-2 were no longer randomised and were all assigned to receive 6 × eBEACOPP and patients with negative PET-2 were randomly assigned to 6 × eBEACOPP (standard) or 4 × eBEACOPP (experimental). Randomisation was done centrally using the minimisation method including a random component, stratified according to centre, age (<45 vs ≥45 years), stage (IIB, IIIA vs IIIB, IV), international prognostic score (0-2 vs 3-7), and sex. eBEACOPP was given as previously described; rituximab was given intravenously at a dose of 375 mg/m2 (maximum total dose 700 mg). The primary objectives were to show superiority of the experimental treatment in the PET-2-positive cohort, and to show non-inferiority of the experimental treatment in the PET-2-negative cohort in terms of the primary endpoint, progression-free survival. We defined non-inferiority as an absolute difference of 6% in the 5-year progression-free survival estimates. Primary analyses in the PET-2-negative cohort were per protocol; all other analyses were by intention to treat. This trial was registered with ClinicalTrials.gov, number NCT00515554. FINDINGS: Between May 14, 2008, and July 18, 2014, we recruited 2101 patients, of whom 137 were found ineligible before randomisation and a further 19 were found ineligible after randomisation. Among 434 randomised patients (217 per arm) with positive PET-2, 5-year progression-free survival was 89·7% (95% CI 85·4-94·0) with eBEACOPP and 88·1% (83·5-92·7) with R-eBEACOPP (log-rank p=0·46). Patients with negative PET-2 randomly assigned to either 8 × eBEACOPP or 6 × eBEACOPP (n=504) or 4 × eBEACOPP (n=501) had 5-year progression-free survival of 90·8% (95% CI 87·9-93·7) and 92·2% (89·4-95·0), respectively (difference 1·4%, 95% CI -2·7 to 5·4). 4 × eBEACOPP was associated with fewer severe infections (40 [8%] of 498 vs 75 [15%] of 502) and organ toxicities (38 [8%] of 498 vs 91 [18%] of 502) than were 8 × eBEACOPP or 6 × eBEACOPP in PET-2-negative patients. Ten treatment-related deaths occurred: four in the PET-2-positive cohort (one [<1%] in the 8 × eBEACOPP group, three [1%] in the 8 × R-eBEACOPP group) and six in the PET-2-negative group (six [1%] in the 8 × eBEACOPP or 6 × eBEACOPP group). INTERPRETATION: The favourable outcome of patients treated with eBEACOPP could not be improved by adding rituximab after positive PET-2. PET-2 negativity allows reduction to only four cycles of eBEACOPP without loss of tumour control. PET-2-guided eBEACOPP provides outstanding efficacy for all patients and increases overall survival by reducing treatment-related risks for patients with negative PET-2. We recommend this PET-2-guided treatment strategy for patients with advanced-stage Hodgkin's lymphoma. FUNDING: Deutsche Krebshilfe, Swiss State Secretariat for Education and Research, and Roche Pharma AG.

Dual targeting of MCL1 and NOXA as effective strategy for treatment of mantle cell lymphoma.

Imbalances in the composition of BCL2 family proteins contribute to tumourigenesis and therapy resistance of mantle cell lymphoma (MCL), making these proteins attractive therapy targets. We studied the efficiency of dual targeting the NOXA/MCL1 axis by combining fatty acid synthase inhibitors (NOXA stabilization) with the CDK inhibitor Dinaciclib (MCL1 reduction). This combination synergistically induced apoptosis in cell lines and primary MCL cells and led to almost complete inhibition of tumour progression in a mouse model. Apoptosis was NOXA-dependent and correlated with the NOXA/MCL1 ratio, highlighting the importance of the NOXA/MCL1 balance for effective cell death induction in MCL.

An analysis of the role of follicular lymphoma-associated fibroblasts to promote tumor cell viability following drug-induced apoptosis.

Treatment response of follicular lymphomas (FL) is highly variable. We, therefore, investigated the role of FL cancer-associated fibroblasts (CAFs) on tumor cell viability, in particular in response to treatment with cytotoxic drugs. Stromal cells outgrown from FL patients were characterized and pure CAF populations were co-cultivated with FL cells. To analyze fibroblast-mediated effects, cells in co-culture were treated with ABT-737 and Bortezomib. The adherent cell population was positive for all fibroblastic markers tested and showed increased mRNA-expression of the activation marker FAP. No effect on FL cell viability was noted when co-cultivating them with CAFs. However, stromal cells protected tumor cells from apoptosis in response to cytotoxic treatment. This might be explained by mRNA-induction of ABCC1 and ABCG2 and up-regulation of BCL2L1 in FL cells. Our finding of protective mechanisms mediated by CAFs is of pivotal impact for further studies of cytotoxic agents in FL.