540 Background: Hepatocellular carcinoma (HCC) is a cancer with poor prognosis and rising incidence. The combination of atezolizumab plus bevacizumab (A+B) prolongs survival as 1 st line therapy in advanced HCC (aHCC) but confers a rare risk of serious bleeding. HCC brain metastases (BM) have high hemorrhage rates and contraindicate the A+B regimen. Alternative immunotherapies also prolong survival without increased bleeding risk. We conducted a retrospective review of a large, diverse, cancer center registry to estimate the prevalence of and identify clinical characteristics associated with BM in aHCC. Methods: The University of California, San Francisco (UCSF) Helen Diller Family Comprehensive Cancer Center (HDFCCC) registry was queried for new cases of HCC between 2004 and 2022. AJCC stage III or IV were defined as aHCC. Cases with central nervous system (CNS) metastases (including brain as well as skull, face, or orbit as adjacent high-risk sites) at diagnosis were identified. Key clinical covariates including demographics, liver disease etiology, and symptomatology were described. Results: Among 4002 new HCC cases, 832 were classified as aHCC. 12/832 (1.4%, 95% CI: 0.8, 2.5) had synchronous BM. Key demographics are displayed in Table. 10/12 (83%) patients with BM were symptomatic, including headache (25%), neurologic deficits (67%), and/or syncope (8%). Bleeding complications and/or hemorrhagic features were reported in 17%. Conclusions: BM are rare at diagnosis with aHCC, present in only 1.4% of this registry dataset. The majority (83%) were symptomatic, suggesting that routine CNS imaging may not have clinical utility in asymptomatic patients. A high proportion with BM at diagnosis had viral etiology. Limitations of this retrospective registry analysis include potential for underdiagnosis in asymptomatic patients and incomplete data for clinical covariates. Clinical characteristics of aHCC cases with BM at diagnosis between 2004-2022 in UCSF HDFCCC Registry. Overall aHCC Cases (N=832) Cases with BM (n=12) Median age (range) (yrs.) 61 (8-92) 60 (48-65) Race/ethnicity (%)AsianBlackCaucasianHispanic (any race) 29105715 2586717 Gender (%)MaleFemale 7921 7525 Etiology (%)Viral hepatitisUnknown/negative 2971 7525 Symptomatic BM (%)HeadacheNeurologic deficitsSyncope NA 8325678 Hemorrhagic BM (%) NA 17

Hepatitis B virus (HBV) infections promote liver cancer initiation by inducing inflammation and cellular stress. Despite a primarily indirect effect on oncogenesis, HBV is associated with a recurrent genomic phenotype in hepatocellular carcinoma (HCC), suggesting that it impacts the biology of established HCC. Characterization of the interaction of HBV with host proteins and the mechanistic contributions of HBV to HCC initiation and maintenance could provide insights into HCC biology and uncover therapeutic vulnerabilities. In this study, we used affinity purification mass spectrometry to comprehensively map a network of 145 physical interactions between HBV and human proteins in HCC. A subset of the host factors targeted by HBV proteins were preferentially mutated in non-HBV-associated HCC, suggesting that their interaction with HBV influences HCC biology. HBV interacted with proteins involved in mRNA splicing, mitogenic signaling, and DNA repair, with the latter set interacting with the HBV oncoprotein X (HBx). HBx remodeled the PP2A phosphatase complex by excluding striatin regulatory subunits from the PP2A holoenzyme, and the HBx effects on PP2A caused Hippo kinase activation. In parallel, HBx activated mTOR complex 2, which can prevent YAP degradation. mTOR complex 2-mediated upregulation of YAP was observed in human HCC specimens and mouse HCC models and could be targeted with mTOR kinase inhibitors. Thus, HBV interaction with host proteins rewires HCC signaling rather than directly activating mitogenic pathways, providing an alternative paradigm for the cellular effects of a tumor-promoting virus. Significance: Integrative proteomic and genomic analysis of HBV/host interactions illuminated modifiers of hepatocellular carcinoma behavior and key signaling mechanisms in advanced disease, which suggested that HBV may have therapeutically actionable effects.

The DNAJ-PKAc fusion kinase is a defining feature of the adolescent liver cancer fibrolamellar carcinoma (FLC). A single lesion on chromosome 19 generates this mutant kinase by creating a fused gene encoding the chaperonin binding domain of Hsp40 (DNAJ) in frame with the catalytic core of protein kinase A (PKAc). FLC tumors are notoriously resistant to standard chemotherapies. Aberrant kinase activity is assumed to be a contributing factor. Yet recruitment of binding partners, such as the chaperone Hsp70, implies that the scaffolding function of DNAJ- PKAc may also underlie pathogenesis. By combining proximity proteomics with biochemical analyses and photoactivation live-cell imaging we demonstrate that DNAJ-PKAc is not constrained by A-kinase anchoring proteins. Consequently, the fusion kinase phosphorylates a unique array of substrates. One validated DNAJ-PKAc target is the Bcl-2 associated athanogene 2 (BAG2), a co-chaperone recruited to the fusion kinase through association with Hsp70. Immunoblot and immunohistochemical analyses of FLC patient samples correlate increased levels of BAG2 with advanced disease and metastatic recurrences. BAG2 is linked to Bcl-2, an anti-apoptotic factor that delays cell death. Pharmacological approaches tested if the DNAJ- PKAc/Hsp70/BAG2 axis contributes to chemotherapeutic resistance in AML12 DNAJ-PKAc hepatocyte cell lines using the DNA damaging agent etoposide and the Bcl-2 inhibitor navitoclax. Wildtype AML12 cells were susceptible to each drug alone and in combination. In contrast, AML12 DNAJ-PKAc cells were moderately affected by etoposide, resistant to navitoclax, but markedly susceptible to the drug combination. These studies implicate BAG2 as a biomarker for advanced FLC and a chemotherapeutic resistance factor in DNAJ-PKAc signaling scaffolds.

Hepatocellular carcinoma (HCC) is a leading cause of cancer death globally and is rising in incidence. Until recently, treatment options for patients with advanced stages of HCC have been limited to antiangiogenic therapies with modest improvements in overall survival. The emerging role of immunotherapy with immune checkpoint inhibitors (ICI) in oncology has led to a rapid expansion in treatment options and improvements in outcomes for patients with advanced stages of HCC. Recent clinical trials have shown meaningful survival improvement in patients treated with the combination of bevacizumab and atezolizumab, as well as with the combination of tremelimumab with durvalumab, resulting in regulatory approvals of these regimens as frontline therapy. Beyond improvements in overall survival, ICI-based combination regimens achieve higher rates of durable treatment response than multikinase inhibitors and have favorable side effect profiles. With the emergence of doublet anti-angiogenic and immune checkpoint inhibitor (ICI) and dual ICI combinations, individualized therapy is now possible for patients based on co-morbidity profiles and other factors. These more potent systemic therapies are also being tested in earlier stages of disease and in combination with loco-regional therapies such as trans-arterial chemoembolization and stereotactic body radiotherapy. We summarize these advances and emerging therapeutic combinations currently in clinical trials.

Genetic alterations that activate protein kinase A (PKA) are found in many tumor types. Yet, their downstream oncogenic signaling mechanisms are poorly understood. We used global phosphoproteomics and kinase activity profiling to map conserved signaling outputs driven by a range of genetic changes that activate PKA in human cancer. Two signaling networks were identified downstream of PKA: RAS/MAPK components and an Aurora Kinase A (AURKA)/glycogen synthase kinase (GSK3) sub-network with activity toward MYC oncoproteins. Findings were validated in two PKA-dependent cancer models: a novel, patient-derived fibrolamellar carcinoma (FLC) line that expresses a DNAJ-PKAc fusion and a PKA-addicted melanoma model with a mutant type I PKA regulatory subunit. We identify PKA signals that can influence both de novo translation and stability of the proto-oncogene c-MYC. However, the primary mechanism of PKA effects on MYC in our cell models was translation and could be blocked with the eIF4A inhibitor zotatifin. This compound dramatically reduced c-MYC expression and inhibited FLC cell line growth in vitro. Thus, targeting PKA effects on translation is a potential treatment strategy for FLC and other PKA-driven cancers.

Summary Infection by hepatitis B virus (HBV) increases risk for liver cancer by inducing inflammation, cellular stress and cell death. To elucidate the molecular pathways by which HBV promotes cancer development and progression, we used affinity purification mass spectrometry to comprehensively map a network of 145 physical interactions between HBV and human host proteins in hepatocellular carcinoma (HCC). We find that viral proteins target host factors that are preferentially mutated in non-HBV-associated HCC, implicating cancer pathways whose interaction with HBV plays a role in HCC. Focusing on proteins that directly interact with the HBV oncoprotein X (HBx), we show that HBx remodels the PP2A phosphatase complex, altering its effect on tumor signaling. HBx excludes striatin-family regulatory subunits from PP2A, causing Hippo kinase activation and unmasking a requirement for mTOR complex 2 to maintain expression of the YAP oncoprotein in HCC. Thus, HBV rewires HCC to expose potentially targetable signaling dependencies. Significance Precision medicine has revolutionized cancer treatment but remains elusive for HCC. We used proteomics to define HBV/host interactions and integrated them with HCC mutations. The results implicate modifiers of HCC behavior via remodeling of host complexes and illuminate new biological mechanisms in advanced disease for therapeutic investigation.

Background: HBV-associated HCC has distinct molecular characteristics and worse outcomes compared to non-HBV HCC. We hypothesized that HBV infection might introduce targetable dependencies specific to HBV-associated HCC. Here, we demonstrate the utility of a computational strategy integrating genomic, network and survival analysis for identifying potential therapeutic targets in HBV-associated HCC. Methods: RNA-Seq and CRISPR dependency screening data for 22 HCC cell lines were obtained from the Cancer Dependency Map (DepMap). Cell lines were classified as HBV RNA+ if they harbored more than 40 HBV RNA reads, measured using GATK PathSeq software. Separately, whole genome CRISPRi dependency screening was performed in Hep3B and SNU-368 cells with doxycycline (dox)- inducible HBx expression. Genes where HBV RNA+ status (for DepMap) or HBx expression (for dox-inducible Hep3B/SNU-368) were significantly associated with negative dependency score were classified as HBV differential dependencies. To identify shared targets across datasets, these dependencies were evaluated using two network analysis techniques: the MCODE graph clustering algorithm and network propagation. Finally, RNA-Seq and survival data for 371 HCC cases were obtained from TCGA, and for each gene, a Cox multivariate model was used to evaluate whether the combination of decreased RNA-Seq expression and HBV RNA+ status was associated with increased survival. Results: 10 of 22 DepMap HCC cell lines were HBV RNA+. From DepMap and dox-inducible Hep3B/SNU-368 dependency screening data, 674 HBV differential dependencies were identified (Wilcoxon p < 0.05 for all). MCODE analysis identified enriched gene networks harboring multiple dependencies, including clusters associated with chromatin remodeling, the DNA damage response, and MAPK/ERK and Wnt signaling. Network propagation identified 236 enriched genes (empiric p < 0.005 for all), including the histone deacetylase HDAC1 and transcription factors ELK1, HNF4A and NRF1. Notably, HDAC1 was significant in both the MCODE and network propagation analyses, and in multivariate analysis of TCGA clinical data, decreased HDAC1 expression was associated with increased survival in HBV RNA+ HCC cases (HR for death 0.10, 95% CI 0.03-0.40, p = 0.0009). Conclusions: Measurement of HBV RNA in HCC cell lines identified a set of HBV- associated differential gene dependencies for which network analysis showed enrichment of several genes/gene clusters, including HDAC1, ELK1, HNF4A and NRF1. Survival analysis highlighted HDAC1 as a potential target where decreased expression was associated with increased survival in HBV RNA+ HCC cases in TCGA. Beyond nominating HDAC1, this study demonstrates the utility of a computational strategy integrating genomic, network and survival analysis for evaluating therapeutic targets in a virus-associated cancer. Citation Format: Huat Chye Lim, Rigney Turnham, Katherine Lo, Yeonjoo Hwang, John Gordan. Computational identification of targetable dependencies in hepatocellular carcinoma (HCC) associated with hepatitis B virus (HBV) replication [abstract]. In: Proceedings of the AACR Special Conference: Advances in the Pathogenesis and Molecular Therapies of Liver Cancer; 2022 May 5-8; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(17_Suppl):Abstract nr PR01.

Although precision medicine has revolutionized the treatment for other solid tumors, comprehensive genome profiling of hepatocellular carcinoma (HCC) has demonstrated that there are few oncogenic mutational drivers. HCC arises nearly universally in the context of co-morbid hepatitis, driven by hepatitis C virus or hepatitis B virus (HBV). Previous work has highlighted the effects of HBV protein X (HBx) on signaling and proliferation. However, it remains unclear how these signaling changes interact with the stress imposed by HBV replication. We hypothesize that HBV replication and maintenance of HBV proteins like HBx creates specific vulnerabilities that can be uncovered and exploited. We performed whole-genome clustered regularly interspaced short palindromic repeat interference (CRISPRi) screening in two engineered, patient-derived HBV+ cell models, Hep3B and SNU-368, with cellular proliferation as the readout. A conditional induction of HBx was used to overexpress HBx in each cell model for the whole genome CRISPRi screen. Genes where HBx expression was significantly associated with a more negative dependency score were classified as HBV differential dependencies. 37 genes were identified as shared HBV-induced dependencies across both cell lines. Of these, 16 were also differentially expressed in HCC specimens with ongoing HBV replication vs. non-HBV expressing tumors collected in The Cancer Genome Atlas (TCGA), suggesting in vivo selective pressure to alter the expression of these genes. We focused on Zinc Fingers and Homeoboxes 2 (ZHX2) and methionine adenosyltransferase 2A (MAT2A). ZHX2 was identified as an HCC tumor suppressor, and data from TCGA showed differential gene expression of ZHX2 in HBV+HCC. Validation of ZHX2 sgRNA knockdown confirmed that ZHX2 knockdown preferentially reduced cell proliferation in the presence of HBx, consistent with an HBV-induced dependency. ZHX2 also can activate the HIF pathway; we identified alterations of HIF targets with ZHX2 knockdown and HBx expression. Similarly, MAT2A knockdown in HBV+HCC cell lines showed decreased cell proliferation with HBx expression. MAT2A is an emerging therapeutic target, with sensitivity to MAT2A inhibitors conferred by deletions in methylthioadenosine phosphorylase (MTAP), seen in 3% of HCC. Ongoing investigations include alteration of splicing and cell cycle changes with depletion of MAT2A in the presence of HBx. With small molecule inhibitors of MAT2A in clinical development, this finding may be therapeutically actionable. Thus, using functional genomics to interrogate HBV-associated gene dependencies has illuminated the biology of HCC and identified candidate therapeutic targets for pre-clinical validation. Citation Format: Rigney E Turnham, Huat Chye Lim, Lucille Ferret, Katherine Lo, LeeAnn Wang, Alex Choi, John D Gordan. Uncovering hepatitis B virus-induced signaling changes in hepatocellular carcinoma [abstract]. In: Proceedings of the AACR Special Conference: Advances in the Pathogenesis and Molecular Therapies of Liver Cancer; 2022 May 5-8; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(17_Suppl):Abstract nr PO023.

Viral hepatitis promotes hepatocellular carcinoma (HCC) initiation by inducing inflammation, cellular stress and cell death. However, the cell-intrinsic effects of viral infection in advanced HCC remain unclear. We used affinity purification mass spectrometry to develop a complete map of 145 interactions among Hepatitis B Virus (HBV) and host proteins in the HUH7 HCC tumor cell line, identifying known and novel HBV/host protein-protein interactions. We integrated this map with HCC genomes, identifying 61 proteins with preferential mutation in non-HBV HCC, suggesting that their interaction with HBV plays a role in cancer. Focusing on proteins that directly interact with the HBV oncoprotein X (HBx), we found that HBx rewires the effect of the PP2A phosphatase on HCC signaling. HBx binding excluded striatin-family regulatory subunits from the PP2A complex, causing Hippo kinase activation. This effect creates a requirement for integrin signaling to mTOR complex 2 to maintain expression of the YAP oncoprotein, critical for HCC growth. Thus, HBV rewires HCC signaling and may promote targetable dependencies. Citation Format: John Gordan, Adriana Pitea, Rigney E Turnham, Manon Eckhardt, Gwendolyn M Jang, Huat Lim, Alex L Choi, Sourav Bandyopadhyay, Danielle Swaney, Kevan Shokat, Trey Ideker, Nevan Krogan. HBV alters YAP regulation in liver cancer by remodeling PP2A complexes [abstract]. In: Proceedings of the AACR Special Conference: Advances in the Pathogenesis and Molecular Therapies of Liver Cancer; 2022 May 5-8; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(17_Suppl):Abstract nr PO017.

Hepatitis B virus (HBV) infection contributes to hepatocellular carcinoma (HCC) initiation and is associated with worse outcomes. Many prior studies of HBV-related HCC have not accounted for potential heterogeneity among HBV-related tumors by assessing whether HBV activity is present in tumor tissue. Here, we measured tumor HBV RNA, a proxy for viral activity, and investigated the association between HBV RNA status and several clinicogenomic characteristics. We obtained clinical, mutation, RNA-Seq and survival data for 439 HCC tumors from The Cancer Genome Atlas and International Cancer Genome Consortium. Tumors were classified as HBV RNA positive if they harbored >1 HBV RNA read per million human reads. We investigated the association between HBV RNA status and nonsynonymous somatic mutations, gene set expression, homologous recombination deficiency (HRD) score and mutation-specific survival. HBV RNA positive status was associated with higher nonsynonymous mutation rates of multiple genes, including TP53 and CDKN2A , while HBV RNA negative status was associated with higher nonsynonymous BAP1 mutation rate. HBV RNA positive status was also associated with increased transcription of genes involved in multiple DNA damage repair pathways, genes upregulated by MYC and mTORC1, and genes overexpressed in several HCC subclasses associated with a proliferative phenotype. Further, HBV RNA positive status was associated with increased three-biomarker HRD score (22.2 for HBV RNA+ vs. 16.0 for HBV RNA-). Finally, HBV RNA status was associated with multiple mutation-specific survival differences, including decreased survival for HBV RNA positive patients with nonsynonymous KEAP1 mutations compared to those without (hazard ratio 4.26). HCC tumors harboring genomic evidence of HBV activity therefore constitute a distinct HCC subset characterized by specific differences in nonsynonymous mutations, gene set expression, three-biomarker HRD score and mutation-specific survival.

Hepatocellular carcinoma (HCC) is the second leading cause of cancer death worldwide. Advanced HCC has proven particularly difficult to treat because of a scarcity of clear genetic drivers of cancer progression; thus, there are currently no predictive markers that guide HCC therapy. HCC arises in the context of co-morbid hepatitis due to hepatitis B virus (HBV), hepatitis C (HCV) or fatty liver disease. We hypothesize that protein-protein interactions (PPIs) between viral proteins and HCC genes may contribute to tumor initiation and maintenance. In order to characterize these PPIs, we performed affinity purification - mass spectrometry (APMS), defining 145 HBV/host PPIs including known and novel interacting partners. We next used a network propagation algorithm to identify host genes and protein complexes that were preferentially mutated in the absence of HBV infection. HBV is a small DNA virus, with 4 genes of which only one has enzymatic activity, raising a question as to how HBV interaction modifies host behavior. Using AP-MS of host proteins, we found that the HBV X protein (HBx) remodels multiple host protein complexes through direct interaction. These physical effects on complex components result in distinct biochemical behavior from the CRL4 E3 ubiquitin ligase complex as well as the phosphatase PP2A, as determined through global phosphoproteomics and ubiquitin analysis. We show that this remodeling driven by HBx substantially changes cellular protein turnover and downstream signaling dynamics. We followed this up with assessments of cellular viability and proliferation in response to pharmacological inhibition or CRISPRi-based knockdown of HBx effectors. Our data support a model where HBV proteins alter the components and behavior of key regulatory protein complexes in the cell, altering tumor behavior and raising the possibility of precision therapeutics for HCC. Citation Format: John D. Gordan, Adriana Pitea, Manon Eckhardt, Gwendolyn Jang, Rigney E. Turnham, Alex L M. Choi, John Von Dollen, Huat C. Lim, Elizabeth F. Thayer, R. Katie Kelley, Danielle L. Swaney, Wei Zhang, Fabian J. Theis, Trey Ideker, Nevan J. Krogan. Hepatitis B virus remodels host protein interaction networks to generate distinct cellular dependencies [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 4891.

e15593 Background: HBV replication contributes to HCC initiation and is associated with worse patient outcomes. Prior tumor genomic studies of HBV-positive and -negative (HBV+/-) HCC have used detection of HBV surface antigen (HBsAg) in serum to annotate HBV status. However, a substantial proportion of HBsAg+ patients lack HBV replication in tumor, suggesting a potentially distinct patient subset. In this study, we determined HBV status by measuring tumor HBV RNA, a proxy for active replication. We then investigated HBV RNA+/- association with somatic mutations, gene sets, homologous recombination deficiency (HRD) and tumor mutation burden (TMB). Methods: RNA-Seq data for 371 HCC tumors were obtained from TCGA. Tumors were classified as HBV RNA+ if they harbored more than 1 HBV RNA read per million human reads, as measured using GATK PathSeq software. Associations between HBV RNA status and somatic mutations, gene sets, HRD and TMB were investigated. HRD score was calculated as the sum of 3 independent HRD measures (large scale state transitions, loss of heterozygosity and telomeric allelic imbalance). Results: HBV RNA+ status was associated with a higher rate of nonsynonymous somatic mutations in multiple genes, including the tumor suppressors TP53, CDKN2A, CHD5 and TET1, as well as AXIN2 and the proto-oncogene BCL11A ( p < 0.05 for all), while HBV RNA- status was associated with a higher rate of nonsynonymous mutations in the chromatin modifier BAP1 ( p = 0.03). In gene set enrichment analysis of normalized RNA-Seq expression data, HBV RNA+ status was associated with increased transcription of DNA repair genes, as well as genes upregulated by mTORC1 and MYC (FDR < 0.03 for all). HBV RNA status was also associated with HRD score (22.19 for HBV RNA+ vs. 15.97 for HBV RNA-, p = 1e-6), but not with TMB. A substantial subset of HBV RNA+ patients (33/100) were not annotated as HBV+ in the TCGA clinical database. Conclusions: HBV status based on tumor HBV RNA detection identifies a genetically distinct subset within all HBV-infected HCC patients that is associated with nonsynonymous somatic mutations in several genes and differential transcription of gene sets, some of which have not been previously reported, as well as with HRD score. These findings suggest potential for differential responsiveness to targeted therapies.

Abdominal pain is a common complaint in patients who are older, and has a broad differential diagnosis. This case of an elderly woman with a complicated surgical history who developed progressive subacute-on-chronic abdominal pain highlights the importance of keeping under consideration etiologies that more commonly affect patients who are younger but also exhibit a second incidence peak later in life. In addition, this case illustrates the necessity of revisiting the diagnostic workup when significant aspects of a patient’s presentation remain unexplained by a working diagnosis.

Biliary tract cancers such as cholangiocarcinoma represent a heterogeneous group of cancers that can be difficult to diagnose. Recent comprehensive genomic analyses in large cholangiocarcinoma cohorts have defined important molecular subgroups within cholangiocarcinoma that may relate to anatomic location and etiology [1], [2], [3], [4] and may predict responsiveness to targeted therapies in development [5], [6], [7]. These emerging data highlight the potential for tumor genomics to inform diagnosis and treatment options in this challenging tumor type. We report the case of a patient with a germline BRCA1 mutation who presented with a cholangiocarcinoma driven by the novel YWHAZ-BRAF fusion. Hybrid capture-based DNA sequencing and copy number analysis performed as part of clinical care demonstrated that two later-occurring tumors were clonally derived from the primary cholangiocarcinoma rather than distinct new primaries, revealing an unusual pattern of late metachronous metastasis. We discuss the clinical significance of these genetic alterations and their relevance to therapeutic strategies.KEY POINTS:Hybrid capture-based next-generation DNA sequencing assays can provide diagnostic clarity in patients with unusual patterns of metastasis and recurrence in which the pathologic diagnosis is ambiguous.To our knowledge, this is the first reported case of a YWHAZ-BRAF fusion in pancreaticobiliary cancer, and a very rare case of cholangiocarcinoma in the setting of a germline BRCA1 mutation.The patient's BRCA1 mutation and YWHAZ-BRAF fusion constitute potential targets for future therapy.