Hypoxia Inducible Factor-independent functions for the von Hippel-Lindau tumor suppressor gene

Inactivating mutations of the von Hippel-Lindau gene (VHL) on chromosome 3p have been associated with the autosomal dominant VHL disease, characterized by extensively vascularized tumors and cysts in different organs, as well as the majority of conventional kidney cancers. The VHL gene product regulates the ubiquitination and subsequent degradation of hypoxia inducible factor (HIF), an important transcriptional activator of the genetic program triggered by hypoxia. The absence of functional VHL, thus, artificially stabilizes HIF and induces a cellular response to perceived low-oxygen tension. This illegitimate HIF signalling under normoxic conditions is likely to contribute to the extensive vascularization observed in VHL-related lesions. In the first chapter we examine the arguments for alternative function for the VHL related tumors. The data presented in the second chapter contributes the concept of a HIF-independent function for the VHL gene. Here we present the outcome of a microarray analysis of VHL-positive vs. VHL-negative cells. In these experiments we find a known VHL-interacting partener: fibronectin that is regulated by VHL at the mRNA level, independently of hypoxia. The third, fourth and fifth chapters address what the molecular mechanism of the VHL-mediated HIF-independent function could be. As discussed in the first chapter our "prime suspect" to determine the HIF-independent function for VHL lies within the N-terminal acidic domain, which has not previously been assigned a function. We show that the acidic domain of VHL can be phosphorylated and that this modification is essential for tumor suppression in vivo. The acidic domain is also involved in binding the kinesin-2 complex and this interaction between the kinesin-2 complex and VHL plays a role in promoting microtubule stability in the cell periphery. Furthermore, we show that the kinesin-2 complex and VHL cooperate in the formation of primary cilia. These data represent the first pieces of experimental evidence that the acidic domain has a function. The model that arises from the data presented in these chapters is that the acidic domain plays an important role in determining the HIF-independent role for VHL; however, the exact molecular mechanism needs to be elucidated. The sixth chapter deals with a somewhat different aspect of VHL biology being the regulation of VHL expression and its role in the physiology of the intestine. We found that the expression of VHL was regulated by active wnt-signaling and displays the expression pattern of a typical wnt-signaling target in the intestinal mucosa. Interestingly there was reciprocal expression of HIF under normoxic conditions. These data show for the first time that regulation of expression of VHL has functional consequences and can lead to normoxic activation of HIF. The HIF-independent role of VHL has been made plausible with the data represented in this thesis, however the molecular nature has not yet been clarified fully. For the optimal treatment of patients with VHL disease and those carrying sporadic renal cell carcinomas with VHL mutations, the elucidation of this mechanism is essential. These insights will allow us to design therapies that interfere with this mechanism and thereby target the tumor in a more specific way

Phase II study (KAMELEON) of single-agent T-DM1 in patients with HER2-positive advanced urothelial bladder cancer or pancreatic cancer/cholangiocarcinoma

HER2-positive; Pancreatic cancer; Urothelial bladder cancerHER2 positivo; Cáncer de páncreas; Cáncer de vejiga urotelialHER2-positiu; Càncer de pàncrees; Càncer de bufeta urotelialThe antibody-drug conjugate trastuzumab emtansine (T-DM1) is approved for human epidermal growth factor receptor 2 (HER2/ERBB2)–positive breast cancer. We aimed to study tumor HER2 expression and its effects on T-DM1 responses in patients with HER2-positive urothelial bladder cancer (UBC) or pancreatic cancer (PC)/cholangiocarcinoma (CC). In the phase II KAMELEON study (NCT02999672), HER2 status was centrally assessed by immunohistochemistry, with positivity defined as non-focal homogeneous or heterogeneous overexpression of HER2 in ≥30% of stained cells. We also performed exploratory biomarker analyses (e.g., gene-protein assay) on tissue samples collected from study participants and consenting patients who failed screening. Of the 284 patients successfully screened for HER2 status (UBC, n = 69; PC/CC, n = 215), 13 with UBC, four with PC, and three with CC fulfilled eligibility criteria. Due to recruitment difficulty, the sponsor terminated KAMELEON prematurely. Of the five responders in the UBC cohort (overall response rate, 38.5%), HER2 expression was heterogeneous in two and homogeneous in three. The one responder in the PC/CC cohort had PC, and the tumor displayed homogeneous expression. In the biomarker-evaluable population, composed of screen-failed and enrolled patients, 24.3% (9/37), 1.5% (1/66), and 8.2% (4/49) of those with UBC, PC, or CC, respectively, had HER2-positive tumors. In a gene-protein assay combining in situ hybridization with immunohistochemistry, greater HER2 homogeneity was associated with increased ERBB2 amplification ratio. In conclusion, KAMELEON showed that some patients with HER2-positive UBC or PC can respond to T-DM1 and provided insight into the prevalence of HER2 positivity and expression patterns in three non-breast tumor types

A Compendium of AR Splice Variants in Metastatic Castration-Resistant Prostate Cancer

Treatment-induced AR alterations, including AR alternative splice variants (AR-Vs), have been extensively linked to harboring roles in primary and acquired resistance to conventional and next-generation hormonal therapies in prostate cancer and therefore have gained momentum. Our aim was to uniformly determine recurrent AR-Vs in metastatic castration-resistant prostate cancer (mCRPC) using whole transcriptome sequencing in order to assess which AR-Vs might hold potential diagnostic or prognostic relevance in future research. This study reports that in addition to the promising AR-V7 as a biomarker, AR45 and AR-V3 were also seen as recurrent AR-Vs and that the presence of any AR-V could be associated with higher AR expression. With future research, these AR-Vs may therefore harbor similar or complementary roles to AR-V7 as predictive and prognostic biomarkers in mCRPC or as proxies for abundant AR expression.</p

Oligometastatic Prostate Cancer:Results of a Dutch Multidisciplinary Consensus Meeting

Background: Oligometastatic prostate cancer (OMPC) is a heterogeneous disease state that is imperfectly understood, and its clinical implications are unclear. Objective: To determine the consensus of a Dutch multidisciplinary expert panel on biological aspects, treatment goals, and management of OMPC in daily clinical practice. Design, setting, and participants: The study comprised a modified Delphi method including an explorative survey with various statements and questions, followed by a consensus meeting to discuss and determine the agreement with revised statements and related items. The panel consisted of 34 Dutch representatives from urology, medical and radiation oncology, radiology, nuclear medicine, and basic research. Outcome measurements and statistical analysis: Agreement was determined with statements (five-point scale). Consensus was defined as ≥75% panel agreement with a statement. Results and limitations: Consensus existed for 56% of statements. The panel agreed that OMPC comprises a limited metastatic spread in the hormone-sensitive setting, in both the synchronous and the metachronous presentation. Limited metastatic spread was believed to involve three to five metastases and a maximum of two organs. Prostate-specific membrane antigen positron emission tomography/computed tomography scan was currently perceived as the most accurate diagnostic imaging modality. Although there was a consensus that targeted treatment of all metastases in OMPC will delay further dissemination of the disease, opinions on specific treatment regimens were divided. Panel outcomes were limited by the lack of scientific evidence on OMPC. Conclusions: A multidisciplinary panel reached a consensus that OMPC is a specific disease state requiring a tailored treatment approach. OMPC registries and clinical studies should focus on both the biology and the clinical parameters in relation to optimal treatment strategies in synchronous and metachronous OMPC. Patient summary: A group of Dutch medical specialists agreed that prostate cancer patients having few metastases may benefit from a new therapeutic approach. Clinical studies need to determine which treatment is best for each specific situation. A multidisciplinary panel reached consensus that oligometastatic prostate cancer (OMPC) is a specific disease state requiring a tailored treatment approach. OMPC registries and clinical studies should provide insight into the biology and clinical parameters in relation to optimal treatment strategies in synchronous and metachronous OMPC

Testosterone Diminishes Cabazitaxel Efficacy and Intratumoral Accumulation in a Prostate Cancer Xenograft Model

Inactivation of the androgen receptor (AR) pathway by androgen deprivation therapy (ADT) is the mainstay of (metastatic) prostate cancer therapy. Ultimately, the AR pathway will be re-activated despite castrate levels of circulating androgens. Thereby, maintaining its role even in castration resistant prostate cancer (CRPC). The recent STAMPEDE and CHAARTED trials showed that docetaxel in combination with ADT increased survival in hormone sensitive prostate cancer patients, suggesting cross-talk between AR signaling and chemotherapy efficacy. We hypothesized that a similar interaction may also apply for CRPC that is treated with cabazitaxel. We studied the impact of androgen status on the efficacy, pharmacodynamics and -kinetics of cabazitaxel in a unique and clinically relevant patient derived xenograft model of castration resistant disease. We found that cabazitaxel is highly effective in a castrate setting with strongly reduced AR activation, while tumor growth inhibition by cabazitaxel was completely abolished in the presence of high AR pathway activity. Moreover, additional experiments showed that intratumoral cabazitaxel levels were 3.5 times higher in tumors from castrated mice as compared to tumors from androgen-supplemented animals. We confirmed that cabazitaxel pharmacokinetics were not affected by testosterone, suggesting that androgen status might influence cabazitaxel tumor uptake directly. This study reveals the impact of androgen status on cabazitaxel efficacy and supports the potential of combination of taxane chemotherapeutics with AR axis targeting agents

Whole-genome mapping of APOBEC mutagenesis in metastatic urothelial carcinoma identifies driver hotspot mutations and a novel mutational signature

Apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) enzymes mutate specific DNA sequences and hairpin-loop structures, challenging the distinction between passenger and driver hotspot mutations. Here, we characterized 115 whole genomes of metastatic urothelial carcinoma (mUC) to identify APOBEC mutagenic hotspot drivers. APOBEC-associated mutations were detected in 92% of mUCs and were equally distributed across the genome, while APOBEC hotspot mutations (ApoHMs) were enriched in open chromatin. Hairpin loops were frequent targets of didymi (twins in Greek), two hotspot mutations characterized by the APOBEC SBS2 signature, in conjunction with an uncharacterized mutational context (Ap[C&gt;T]). Next, we developed a statistical framework that identified ApoHMs as drivers in coding and non-coding genomic regions of mUCs. Our results and statistical framework were validated in independent cohorts of 23 non-metastatic UCs and 3,744 samples of 17 metastatic cancers, identifying cancer-type-specific drivers. Our study highlights the role of APOBEC in cancer development and may contribute to developing novel targeted therapy options for APOBEC-driven cancers.</p

Whole-genome mapping of APOBEC mutagenesis in metastatic urothelial carcinoma identifies driver hotspot mutations and a novel mutational signature

Apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) enzymes mutate specific DNA sequences and hairpin-loop structures, challenging the distinction between passenger and driver hotspot mutations. Here, we characterized 115 whole genomes of metastatic urothelial carcinoma (mUC) to identify APOBEC mutagenic hotspot drivers. APOBEC-associated mutations were detected in 92% of mUCs and were equally distributed across the genome, while APOBEC hotspot mutations (ApoHMs) were enriched in open chromatin. Hairpin loops were frequent targets of didymi (twins in Greek), two hotspot mutations characterized by the APOBEC SBS2 signature, in conjunction with an uncharacterized mutational context (Ap[C&gt;T]). Next, we developed a statistical framework that identified ApoHMs as drivers in coding and non-coding genomic regions of mUCs. Our results and statistical framework were validated in independent cohorts of 23 non-metastatic UCs and 3,744 samples of 17 metastatic cancers, identifying cancer-type-specific drivers. Our study highlights the role of APOBEC in cancer development and may contribute to developing novel targeted therapy options for APOBEC-driven cancers.</p

A Phase I Trial of the Dual MET Kinase/OCT-2 Inhibitor OMO-1 in Metastatic Solid Malignancies Including MET Exon 14 Mutated Lung Cancer

Introduction: Targeted therapy in non-small cell lung cancer (NSCLC) patients with mesenchymal epithelial transition (MET) exon 14 skipping mutations (METex14) and MET amplifications has improved patients' outcomes. The development of more potent MET kinase inhibitors could further benefit these patients. The aim of this trial is to determine the safety and recommended phase 2 dose (RP2D) of OMO-1 (an oral dual MET kinase/OCT-2 inhibitor) and to assess preliminary clinical efficacy in METex14-positive NSCLC and other MET-positive solid tumors. Materials and Methods: This was a first-in-patient, open-label, multicenter study of OMO-1 in patients with locally advanced or metastatic solid malignancies. A standard 3 + 3 dose escalation design was utilized starting at a dose level of 100 mg BID continuously. Preliminary efficacy was investigated in patients with METex14-positive NSCLC, and MET amplified NSCLC and other solid tumors (MET basket). Results: In the dose-escalation part, 24 patients were included in 5 dose levels ranging from 100 mg twice daily (BID) to 400 mg BID. Most common adverse events (≥ 20%) were nausea, fatigue, vomiting, increased blood creatinine, and headache. The RP2D was determined at 250 mg BID. In the expansion cohorts, 15 patients were included (10 in METex14-positive NSCLC cohort and 5 in MET basket cohort) and received either 200 or 250 mg BID. Eight out of the 10 patients with METex14 positive NSCLC had stable disease as the best response. Conclusion: OMO-1 was tolerated at the dose of 250 mg BID and shows initial signs of MET inhibition and anti-tumor activity in METex14 mutated NSCLC patients.</p

A Phase I Trial of the Dual MET Kinase/OCT-2 Inhibitor OMO-1 in Metastatic Solid Malignancies Including MET Exon 14 Mutated Lung Cancer

Introduction: Targeted therapy in non-small cell lung cancer (NSCLC) patients with mesenchymal epithelial transition (MET) exon 14 skipping mutations (METex14) and MET amplifications has improved patients’ outcomes. The development of more potent MET kinase inhibitors could further benefit these patients. The aim of this trial is to determine the safety and recommended phase 2 dose (RP2D) of OMO-1 (an oral dual MET kinase/OCT-2 inhibitor) and to assess preliminary clinical efficacy in METex14-positive NSCLC and other MET-positive solid tumors.// Materials and Methods: This was a first-in-patient, open-label, multicenter study of OMO-1 in patients with locally advanced or metastatic solid malignancies. A standard 3 + 3 dose escalation design was utilized starting at a dose level of 100 mg BID continuously. Preliminary efficacy was investigated in patients with METex14-positive NSCLC, and MET amplified NSCLC and other solid tumors (MET basket).// Results: In the dose-escalation part, 24 patients were included in 5 dose levels ranging from 100 mg twice daily (BID) to 400 mg BID. Most common adverse events (≥ 20%) were nausea, fatigue, vomiting, increased blood creatinine, and headache. The RP2D was determined at 250 mg BID. In the expansion cohorts, 15 patients were included (10 in METex14-positive NSCLC cohort and 5 in MET basket cohort) and received either 200 or 250 mg BID. Eight out of the 10 patients with METex14 positive NSCLC had stable disease as the best response.// Conclusion: OMO-1 was tolerated at the dose of 250 mg BID and shows initial signs of MET inhibition and anti-tumor activity in METex14 mutated NSCLC patients