Development of a resistance-like phenotype to sorafenib by human hepatocellular carcinoma cells is reversible and can be delayed by metronomic UFT chemotherapy

A real-world pharmacovigilance study of Sorafenib based on the FDA Adverse Event Reporting System

Aims

The primary objective of this study was to closely monitor and identify adverse events (AEs) associated with Sorafenib, a pharmacological therapeutic agent used to treat hepatocellular carcinoma, renal cell carcinoma, and thyroid cancer. The ultimate goal was to optimize patient safety and provide evidence-based guidance for the appropriate use of this drug.

Methods

Reports from the FDA Adverse Event Reporting System (FAERS) database were comprehensively collected and analyzed, covering the first quarter of 2004 to the first quarter of 2024. Disproportionality analysis was performed using robust algorithms for effective data mining to quantify the signals associated with Sorafenib-related AEs.

Results

In total, we identifued 18,624 patients (82,857 AEs in the Sorafenib population) from the collected reports and examined, the occurrence of Sorafenib-induced AEs in 26 organ systems. The study results revealed the presence of the expected AEs, including Diarrhoea, Palmar-plantar erythrodysaesthesia syndrome, Hepatocellular carcinoma, Fatigue, and Rash, which was consistent with the information provided in the drug insert. In addition, unexpected significant AEs, such as Gait inability, Palmoplantar keratoderma and Hyperkeratosis were observed at the preferred term (PT) level. These findings suggest the potential occurrence of adverse reactions not currently documented in drug descriptions.

Conclusion

This study successfully detected new and unforeseen signals associated with Sorafenib-related AEs related to Sorafenib administration, providing important insights into the complex correlations between AEs and Sorafenib use. The results of this study emphasize the critical importance of continuous and vigilant surveillance for the timely identification and effective management of AEs to improve the overall patient safety and wellbeing in the context of Sorafenib therapy.

Mechanisms of drug resistance in HCC

HCC comprises ∼80% of primary liver cancer. HCC is the only major cancer for which death rates have not improved over the last 10 years. Most patients are diagnosed with advanced disease when surgical and locoregional treatments are not feasible or effective. Sorafenib, a multikinase inhibitor targeting cell growth and angiogenesis, was approved for advanced unresectable HCC in 2007. Since then, other multikinase inhibitors have been approved. Lenvatinib was found to be noninferior to sorafenib as a first-line agent. Regorafenib, cabozantinib, and ramucirumab were shown to prolong survival as second-line agents. Advances in immunotherapy for HCC have also added hope for patients, but their efficacy remains limited. A large proportion of patients with advanced HCC gain no long-term benefit from systemic therapy due to primary and acquired drug resistance, which, combined with its rising incidence, keeps HCC a highly fatal disease. This review summarizes mechanisms of primary and acquired resistance to therapy and includes methods for bypassing resistance. It addresses recent advancements in immunotherapy, provides new perspectives on the linkage between drug resistance and molecular etiology of HCC, and evaluates the role of the microbiome in drug resistance. It also discusses alterations in signaling pathways, dysregulation of apoptosis, modulations in the tumor microenvironment, involvement of cancer stem cells, changes in drug metabolism/transport, tumor hypoxia, DNA repair, and the role of microRNAs in drug resistance. Understanding the interplay among these factors will provide guidance on the development of new therapeutic strategies capable of improving patient outcomes.

Coordinated activation of DNMT3a and TET2 in cancer stem cell-like cells initiates and sustains drug resistance in hepatocellular carcinoma

BACKGROUND

Resistance to targeted therapies represents a significant hurdle to successfully treating hepatocellular carcinoma (HCC). While epigenetic abnormalities are critical determinants of HCC relapse and therapeutic resistance, the underlying mechanisms are poorly understood. We aimed to address whether and how dysregulated epigenetic regulators have regulatory and functional communications in establishing and maintaining drug resistance.

METHODS

HCC-resistant cells were characterized by CCK-8, IncuCyte Live-Cell analysis, flow cytometry and wound-healing assays. Target expression was assessed by qPCR and Western blotting. Global and promoter DNA methylation was measured by dotblotting, methylated-DNA immunoprecipitation and enzymatic digestion. Protein interaction and promoter binding of DNMT3a-TET2 were investigated by co-immunoprecipitation, ChIP-qPCR. The regulatory and functional roles of DNMT3a and TET2 were studied by lentivirus infection and puromycin selection. The association of DNMT and TET expression with drug response and survival of HCC patients was assessed by public datasets, spearman correlation coefficients and online tools.

RESULTS

We identified the coordination of DNMT3a and TET2 as an actionable mechanism of drug resistance in HCC. The faster growth and migration of resistant HCC cells were attributed to DNMT3a and TET2 upregulation followed by increased 5mC and 5hmC production. HCC patients with higher DNMT3a and TET2 had a shorter survival time with a less favorable response to sorafenib therapy than those with lower expression. Cancer stem cell-like cells (CSCs) displayed DNMT3a and TET2 overexpression, which were insensitive to sorafenib. Either genetic or pharmacological suppression of DNMT3a or/and TET2 impaired resistant cell growth and oncosphere formation, and restored sorafenib sensitivity. Mechanistically, DNMT3a did not establish a regulatory circuit with TET2, but formed a complex with TET2 and HDAC2. This complex bound the promoters of oncogenes (i.e., CDK1, CCNA2, RASEF), and upregulated them without involving promoter DNA methylation. In contrast, DNMT3a-TET2 crosstalk silences tumor suppressors (i.e., P15, SOCS2) through a corepressor complex with HDAC2 along with increased promoter DNA methylation.

CONCLUSIONS

We demonstrate that DNMT3a and TET2 act coordinately to regulate HCC cell fate in DNA methylation-dependent and -independent manners, representing strong predictors for drug resistance and poor prognosis, and thus are promising therapeutic targets for refractory HCC.

Autophagy and biotransformation affect sorafenib resistance in hepatocellular carcinoma

As sorafenib is a first-line drug for treating advanced hepatocellular carcinoma, sorafenib resistance has historically attracted attention. However, most of this attention has been focused on a series of mechanisms related to drug resistance arising after sorafenib treatment. In this study, we used proteomic techniques to explore the potential mechanisms by which pretreatment factors affect sorafenib resistance. The degree of redundant pathway PI3K/AKT activation, biotransformation capacity, and autophagy level in hepatocellular carcinoma patients prior to sorafenib treatment might affect their sensitivity to sorafenib, in which ADH1A and STING1 are key molecules. These three factors could interact mechanistically to promote tumor cell survival, might be malignant features of tumor cells, and are associated with hepatocellular carcinoma prognosis. Our study suggests possible avenues of therapeutic intervention for patients with sorafenib-resistance and the potential application of immunotherapy with the aim of improving the survival of such patients.

PRECLINICAL MODELS OF LIVER CÂNCER

•In this review, we described different murine models of carcinogenesis: classic models, new transgenic and combined models, that reproduce the key points for HCC and CCA genesis allowing a better understanding of its genetic physiopathological, and environmental abnormalities. •Each model has its advantages, disadvantages, similarities, and differences with the corresponding human disease and should be chosen according to the specificity of the study. Ultimately, those models can also be used for testing new anticancer therapeutic approaches. •Cholangiocarcinoma has been highlighted, with an increase in prevalence. This review has an important role in understanding the pathophysiology and the development of new drugs. Background - This manuscript provides an overview of liver carcinogenesis in murine models of hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA). Objective - A review through MEDLINE and EMBASE was performed to assess articles until August 2022.Methods - Search was conducted of the entire electronic databases and the keywords used was HCC, CCA, carcinogenesis, animal models and liver. Articles exclusion was based on the lack of close relation to the subject. Carcinogenesis models of HCC include HCC induced by senescence in transgenic animals, HCC diet-induced, HCC induced by chemotoxicagents, xenograft, oncogenes, and HCC in transgenic animals inoculated with B and C virus. The models of CCA include the use of dimethylnitrosamine (DMN), diethylnitrosamine (DEN), thioacetamide (TAA), and carbon tetrachloride (CCl4). CCA murine models may also be induced by: CCA cells, genetic manipulation, Smad4, PTEN and p53 knockout, xenograft, and DEN-left median bile duct ligation. Results - In this review, we described different murine models of carcinogenesis that reproduce the key points for HCC and CCA genesis allowing a better understanding of its genetic, physiopathological, and environmental abnormalities. Conclusion - Each model has its advantages, disadvantages, similarities, and differences with the corresponding human disease and should be chosen according to the specificity of the study. Ultimately, those models can also be used for testing new anticancer therapeutic approaches.

Cyclic Metronomic Chemotherapy for Pediatric Tumors: Six Case Reports and a Review of the Literature

We report a retrospective case series of six Hispanic children with tumors treated with metronomic chemotherapy. The six cases comprised one rhabdoid tumor of the kidney, one ependymoma, two medulloblastomas, one neuroblastoma, and a type II neurocytoma of the spine. Treatment included oral cyclophosphamide daily for 21 days alternating with oral etoposide daily for 21 days in a backbone of daily valproic acid and celecoxib. In one case, celecoxib was substituted with sulindac. Of the six patients, three showed complete responses, and all patients showed some response to metronomic therapy with only minor hematologic toxicity. One patient had hemorrhagic gastritis likely associated with NSAIDs while off prophylactic antacids. These data add to a growing body of evidence suggesting that continuous doses of valproic acid and celecoxib coupled with alternating metronomic chemotherapy of agents such as etoposide and cyclophosphamide can produce responses in pediatric tumors relapsing to conventional dose chemotherapy.

Endometriosis-Associated Angiogenesis and Anti-angiogenic Therapy for Endometriosis

Endometriosis is a known estrogen-dependent inflammatory disease affecting reproductive-aged women. Common symptoms include pelvic pain, dysmenorrhea, dyspareunia, heavy menstrual bleeding, and infertility. The exact etiology of endometriosis is largely unknown, and, thus, the diagnosis and treatment of endometriosis are challenging. A complex interplay of many molecular mechanisms is thought to aid in the progression of endometriosis, most notably angiogenesis. This mini-review examines our current knowledge of the molecular etiology of endometriosis-associated angiogenesis and discusses anti-angiogenic therapy, in the blockade of endometriosis-associated angiogenesis, as potential non-hormonal therapy for the treatment of endometriosis.

Efficacy and tolerability of Sorafenib plus metronomic chemotherapy S-1 for advanced hepatocellular carcinoma in preclinical and clinical assessments

OBJECTIVE

Although sorafenib, a molecular targeted agent, has survival benefits for advanced hepatocellular carcinoma (HCC) patients, its disease control rate remains limited. To explore the potential for augmenting its antitumor effect, we assessed the preclinical and clinical efficacy and tolerability of S-1 metronomic chemotherapy (MC) plus sorafenib.

METHODS

Antitumor effects and toxicity of this combination were tested with HAK-1B xenograft and spontaneous HCC mouse models, and a prospective pilot study was performed to compare therapeutic effects and safety between sorafenib plus MC S-1 for 12 advanced HCC cases and the historical control of 363 sorafenib-treated advanced HCC patients at our hospital from July 2011 to June 2015.

RESULTS

In mice, the combination chemotherapy enhanced anti-angiogenic effects, resulting in a stronger tumor hypoxic environment and increased tumor cell apoptosis. Clinically, the objective response rate of the combination chemotherapy was higher than that of sorafenib mono therapy (16.7%; 2/12 vs 5.2%; 19/363, p < 0.05); however, there were no significant differences in overall survival and time to progression. Adverse events including alopecia, thrombocytopenia, and pancreatic enzymes elevation in the combination chemotherapy were higher than those of sorafenib. No patient treated with the combination chemotherapy discontinued treatment due to severe adverse events.

CONCLUSIONS

Sorafenib plus MC S-1 seems to be effective and tolerable for patients with advanced HCC and could be considered a treatment option for these patients.

New frontiers against sorafenib resistance in renal cell carcinoma: From molecular mechanisms to predictive biomarkers

Renal cell carcinoma (RCC) is a highly vascularized tumor and prone to distant metastasis. Sorafenib is the first targeted multikinase inhibitor and first-line chemical drug approved for RCC therapy. In fact, only a small number of RCC patients benefit significantly from sorafenib treatment, while the growing prevalence of sorafenib resistance has become a major obstacle for drug therapy effectivity of sorafenib. The molecular mechanisms of sorafenib resistance in RCC are not completely understood by now. Herein, we comprehensively summarize the underlying mechanisms of sorafenib resistance and molecular biomarkers for predicting sorafenib responsiveness. Moreover, we outline strategies suitable for overcoming sorafenib resistance and prospect potential approaches for identifying biomarkers associated with sorafenib resistance in RCC, which contributes to guide individualized and precision drug therapy.

A Transient Pseudosenescent Secretome Promotes Tumor Growth after Antiangiogenic Therapy Withdrawal

VEGF receptor tyrosine kinase inhibitors (VEGFR TKIs) approved to treat multiple cancer types can promote metastatic disease in certain limited preclinical settings. Here, we show that stopping VEGFR TKI treatment after resistance can lead to rebound tumor growth that is driven by cellular changes resembling senescence-associated secretory phenotypes (SASPs) known to promote cancer progression. A SASP-mimicking antiangiogenic therapy-induced secretome (ATIS) was found to persist during short withdrawal periods, and blockade of known SASP regulators, including mTOR and IL-6, could blunt rebound effects. Critically, senescence hallmarks ultimately reversed after long drug withdrawal periods, suggesting that the transition to a permanent growth-arrested senescent state was incomplete and the hijacking of SASP machinery ultimately transient. These findings may account for the highly diverse and reversible cytokine changes observed in VEGF inhibitor-treated patients, and suggest senescence-targeted therapies ("senotherapeutics")-particularly those that block SASP regulation-may improve outcomes in patients after VEGFR TKI failure.

Complete response of advanced hepatocellular carcinoma achieved by sorafenib dose re-escalation after failure of long-term low-dose-sorafenib treatment combined with transcatheter arterial chemoembolization: a case report

Few reports have described dose re-escalation after long-term low-dose sorafenib leading to good outcomes. Here, we report the case of an 80-year-old woman with advanced hepatocellular carcinoma who achieved complete response from sorafenib dose re-escalation after the failure of long-term low-dose sorafenib treatment combined with transcatheter arterial chemoembolization. Sorafenib therapy was initiated at 400 mg once daily due to old age and low platelet count. 5 months later, this dose was reduced to 200 mg once daily because of adverse events. Best radiological antitumor response by sorafenib treatment alone was judged as stable disease according to the modified Response Evaluation Criteria in Solid Tumors. 1 year later, she showed progressive disease owing to the progression of intrahepatic lesions. She received combination therapy with low-dose sorafenib (200 mg every other day) and transcatheter arterial chemoembolization, which proved relatively effective for three and a half years. Antitumor response by the fourth transcatheter arterial chemoembolization and subsequent low-dose sorafenib was clearly progressive disease. At that time, sorafenib-related adverse events were well-controlled. Sorafenib dose was re-escalated to 200 mg once daily. After this re-escalation, tumor markers declined rapidly, and adverse events remained tolerable. 4 months later, complete response was achieved.

Models for Understanding Resistance to Chemotherapy in Liver Cancer

The lack of response to pharmacological treatment constitutes a substantial limitation in the handling of patients with primary liver cancers (PLCs). The existence of active mechanisms of chemoresistance (MOCs) in hepatocellular carcinoma, cholangiocarcinoma, and hepatoblastoma hampers the usefulness of chemotherapy. A better understanding of MOCs is needed to develop strategies able to overcome drug refractoriness in PLCs. With this aim, several experimental models are commonly used. These include in vitro cell-free assays using subcellular systems; studies with primary cell cultures; cancer cell lines or heterologous expression systems; multicellular models, such as spheroids and organoids; and a variety of in vivo models in rodents, such as subcutaneous and orthotopic tumor xenografts or chemically or genetically induced liver carcinogenesis. Novel methods to perform programmed genomic edition and more efficient techniques to isolate circulating microvesicles offer new opportunities for establishing useful experimental tools for understanding the resistance to chemotherapy in PLCs. In the present review, using three criteria for information organization: (1) level of research; (2) type of MOC; and (3) type of PLC, we have summarized the advantages and limitations of the armamentarium available in the field of pharmacological investigation of PLC chemoresistance.

Sorafenib plus tegafur-uracil (UFT) versus sorafenib as first line systemic treatment for patients with advanced stage HCC: a Phase II trial (ESLC01 study)

Background

Phase II trials found that tegafur–uracil (UFT) is an effective drug in hepatocellular carcinoma (HCC), while preclinical data suggested that its combination with sorafenib may have a promising activity. Our Phase II randomized trial aimed to evaluate efficacy and tolerability of sorafenib plus UFT vs sorafenib in advanced HCC.

Methods

Patients with advanced HCC, with no prior systemic therapy, were randomized to receive either UFT at 125 mg/m² twice daily for 4 out of 5 weeks plus sorafenib at 400 mg twice daily (arm 1) or single agent sorafenib at 400 mg twice daily (arm 2). Primary end point was time to progression (TTP).

Results

Between March 2012 and March 2014, 76 eligible patients – out of 143 preplanned – were randomized. The study was terminated early because of futility. This is the final analysis of the study, after a median follow-up of 10.2 months and death of 86% of randomized patients (n=64). Median TTP was 7.5 months and 8.2 months in arms 1 and 2 respectively (HR: 1.07; 95% CI, 0.52–2.22; P=0.855), while the median overall survival was 8.2 months and 10.5 months respectively (HR: 1.58; 95% CI: 0.90–2.76, P=0.112). Nine patients (25%) in the combination arm discontinued treatment because of toxicity vs eight patients (21.1%) in the sorafenib monotherapy arm (P=0.899).

Conclusion

In patients with advanced HCC, adding UFT to sorafenib is feasible, but it did not improve efficacy outcome over sorafenib monotherapy.

Peroxisome Proliferator-Activated Receptors (PPAR)γ Agonists as Master Modulators of Tumor Tissue

In most clinical trials, thiazolidinediones do not show any relevant anti-cancer activity when used as mono-therapy. Clinical inefficacy contrasts ambiguous pre-clinical data either favoring anti-tumor activity or tumor promotion. However, if thiazolidinediones are combined with additional regulatory active drugs, so-called ‘master modulators’ of tumors, i.e., transcriptional modulators, metronomic low-dose chemotherapy, epigenetically modifying agents, protein binding pro-anakoinotic drugs, such as COX-2 inhibitors, IMiDs, etc., the results indicate clinically relevant communicative reprogramming of tumor tissues, i.e., anakoinosis, meaning ‘communication’ in ancient Greek. The concerted activity of master modulators may multifaceted diversify palliative care or even induce continuous complete remission in refractory metastatic tumor disease and hematologic neoplasia by establishing novel communicative behavior of tumor tissue, the hosting organ, and organism. Re-modulation of gene expression, for example, the up-regulation of tumor suppressor genes, may recover differentiation, apoptosis competence, and leads to cancer control—in contrast to an immediate, ‘poisoning’ with maximal tolerable doses of targeted/cytotoxic therapies. The key for uncovering the therapeutic potential of Peroxisome proliferator-activated receptor γ (PPARγ) agonists is selecting the appropriate combination of master modulators for inducing anakoinosis: Now, anakoinosis is trend setting by establishing a novel therapeutic pillar while overcoming classic obstacles of targeted therapies, such as therapy resistance and (molecular-)genetic tumor heterogeneity.

Rationale for the use of metronomic chemotherapy in gastrointestinal cancer

INTRODUCTION

Metronomic chemotherapy (mCT) is endowed with various properties, ranging from antiangiogenic to immunomodulation, and may revert tumor resistance to conventional drug administration. A variety of antineoplastic agents displayed activity when administered with metronomic schedules in preclinical models of gastrointestinal cancers. However, most of the field is still unexplored.

AREAS COVERED

Herein, the authors review the existing literature from PubMed, concerning the use of mCT in gastrointestinal oncology.

EXPERT OPINION

A mounting body of evidence is emerging in support of mCT as a treatment option for gastrointestinal tumors, but the frequent signs of clinical activity inconsistently translate into a benefit for survival. Research in this field should focus on providing high-quality evidence on the safety and efficacy of mCT, with more prospective, comparative trials; identifying the subgroups of patients for whom mCT would be the best approach; establishing standardized protocols based on mCT pharmacokinetics and pharmacodynamics; developing drug activity biomarkers. mCT is also potentially suitable for combinations with targeted antiangiogenic drugs and may be incorporated with conventional administration into dual regimens.

Liver Protective Effects of Renin-Angiotensin System Inhibition Have No Survival Benefits in Hepatocellular Carcinoma Induced By Repetitive Administration of Diethylnitrosamine in Mice

BACKGROUND:

Preclinical studies have demonstrated that renin-angiotensin system (RAS) signalling has strong tumour-promoting effects and RAS inhibition was associated with improvement in the overall survival in some cancer types including hepatocellular carcinoma (HCC).

OBJECTIVE:

We aimed to investigate the effect of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin-II-receptor blockers (ARBs) on the survival of mice with diethylnitrosamine (DEN) induced HCC.

METHODS:

HCC was induced by weekly i.p. administration of DEN. Mice were treated with sorafenib (SO) (30 mg/kg), perindopril (PE) (1 mg/kg), fosinopril (FO) (2 mg/kg), losartan (LO) (10 mg/kg), PE (1 mg/kg) + SO (30 mg/kg), FO (2 mg/kg) + SO (30 mg/kg), or LO (10 mg/kg) + SO (30 mg/kg). Survival analysis was done using the Kaplan-Meier method, and the log-rank test was used for assessing the significance of difference between groups.

RESULTS:

The administration of PE, FO and LO as monotherapy or as combined with SO resulted in marked improvement in the liver histologic picture with no impact on overall survival of mice.

CONCLUSION:

Interfering the RAS either through the inhibition of ACE or the blockade of angiotensin II type 1 (AT1) receptors has similar effects on the liver of DEN-induced HCC mice and is not associated with longer survival due to detrimental effects of DEN on other organs. Hence, repetitive administration of DEN in such models of HCC is not suitable for mortality assessment studies.

Preclinical impact of high dose intermittent antiangiogenic tyrosine kinase inhibitor pazopanib in intrinsically resistant tumor models

Antiangiogenic tyrosine kinase inhibitors (TKIs) target vascular endothelial growth factor receptors and other receptor tyrosine kinases. As a result of toxicity, the clinical failures or the modest benefits associated with antiangiogenic TKI therapy may be related in some cases to suboptimal drug dosing and scheduling, thereby facilitating resistance. Most antiangiogenic TKIs, including pazopanib, are administered on a continuous daily basis. Here, instead, we evaluated the impact of increasing the dose and administering the drug intermittently. The rationale is that using such protocols, antitumor efficacy could be enhanced by direct tumor cell targeting effects in addition to inhibiting tumor angiogenesis. To test this, we employed two human tumor xenograft models, both of which manifest intrinsic resistance to pazopanib when it is administered continuously: the VHL-wildtype SN12-PM6-1 renal cell carcinoma (RCC) and the metastatic MDA-MB-231/LM2-4 variant breast cancer cell line, when treated as distant metastases. We evaluated four different doses and schedules of pazopanib in the context of primary tumors and advanced metastatic disease, in both models. The RCC model was not converted to drug sensitivity using the intermittent protocol. Using these protocols did not enhance the efficacy when treating primary LM2-4 tumors. However, one of the high-dose intermittent pazopanib protocols increased median survival when treating advanced metastatic disease. In conclusion, these results overall suggest that primary tumors showing sensitivity to continuous pazopanib treatment may predict response to this drug when given at high doses intermittently in the context of advanced metastatic disease, that are otherwise resistant to the conventional protocol.

ERK activation and autophagy impairment are central mediators of irinotecan-induced steatohepatitis

OBJECTIVE

Preoperative chemotherapy with irinotecan is associated with the development of steatohepatitis, which increases the risk of perioperative morbidity and mortality for liver surgery. The molecular mechanisms of this chemotherapeutic complication are widely unknown.

DESIGN

Mechanisms of irinotecan-induced steatohepatitis were studied in primary human hepatocytes in vitro, in mice treated with irinotecan and in liver specimens from irinotecan-treated compared with control patients.

RESULTS

Irinotecan dose-dependently induced lipid accumulation and pro-inflammatory gene expression in hepatocytes. This was accompanied by an impairment of mitochondrial function with reduced expression of carnitine palmitoyltransferase I and an induction of acyl-coenzyme A oxidase-1 (ACOX1), oxidative stress and extracellular signal-regulated kinase (ERK) activation. ERK inhibition prevented irinotecan-induced pro-inflammatory gene expression but had only a slight effect on lipid accumulation. However, irinotecan also induced an impairment of the autophagic flux mediated by alkalisation of lysosomal pH. Re-acidification of lysosomal pH abolished irinotecan-induced autophagy impairment and lipid accumulation. Also in mice, irinotecan treatment induced hepatic ACOX1 expression, ERK phosphorylation and inflammation, as well as impairment of autophagy and significant steatosis. Furthermore, irinotecan-treated patients revealed higher hepatic ERK activity, expression of pro-inflammatory genes and markers indicative for a shift to peroxisomal fatty acid oxidation and an impaired autophagic flux. Pretreatment with the multityrosine kinase inhibitor sorafenib did not affect autophagy impairment and steatosis but significantly reduced ERK phosphorylation and inflammatory response in irinotecan-treated hepatocytes and murine livers.

CONCLUSIONS

Irinotecan induces hepatic steatosis via autophagy impairment and inflammation via ERK activation. Sorafenib appears as a novel therapeutic option for the prevention and treatment of irinotecan-induced inflammation.

COX-2 Forms Regulatory Loop with YAP to Promote Proliferation and Tumorigenesis of Hepatocellular Carcinoma Cells

COX-2 and YAP are shown to be highly associated with hepatocellular carcinoma (HCC) and frequently upregulated during tumor formation. However, despite their importance, whether there is a mutual interaction between COX-2 and YAP and how they regulate each other are not clear. In this paper, we showed that COX-2 overexpression in HCC cell lines resulted in increased levels of YAP mRNA, protein, and its target genes. COX-2 promoted proliferation of HCC cell lines, and knockdown of YAP antagonized this effect. In addition, our results indicated that EP2 and Wnt/β-Catenin mediate the transcriptional induction of YAP by COX-2. On the other hand, YAP increased COX-2 expression at the level of transcription requiring intact TEAD binding sites in the COX-2 promoter. Collectively, these findings indicated that COX-2 is not only a stimulus of YAP but also a target of Hippo-YAP pathway, thus forming a positive feedback circuit, COX-2-PGE₂-EP2-Gαs-β-catenin-YAP-COX-2. In a further study, we showed that inhibition of YAP and COX-2 acted synergistically and more efficiently reduced the growth of HCC cells and tumor formation than either of them alone, suggesting that dual governing of YAP and COX-2 may lead to the discovery of promising therapeutic strategies for HCC patients via blocking this positive feedback loop.

Tumor refractoriness to anti-VEGF therapy

Vascular endothelial growth factor (VEGF) has been identified as the most potent cytokine involved in tumor angiogenesis and metastasis formation. Clinical results of anti-angiogenic therapies targeting VEGF and its receptors are very modest, resulting in a moderate improvement of overall survival. The clinical outcome is associated with the development of resistance and the increased risk of invasion and metastasis. In this article, I have analyzed the principal mechanisms of resistance to VEGF pathway inhibitors, including normalization of tumor blood vessels, hypoxia, recruitment of inflammatory cells and immature myeloid cells, alternative mechanisms of tumor vessel formation, genomic instability of tumor endothelial cells. In this context, the concept and strategies of anti-angiogenic therapies should be extensively re-considered and re-evaluated. In particular, rational combinations of anti-angiogenic agents based on pharmacokinetic and pharmacodynamics data are needed to overcome resistance and it is extremely important to determine the optimal duration and scheduling of anti-VEGF agents.

Treatment options after sorafenib failure in patients with hepatocellular carcinoma

Second line therapy after failure of sorafenib continues to be under study. Prognosis of hepatocellular carcinoma is measured in months, with median overall survival reaching 10.7 months with sorafenib. Because of the modest net benefit sorafenib has contributed, and rising incidence of hepatocellular carcinoma in the world, continued efforts are ongoing to look for efficient upfront, second line, or combination therapies. Herein we review the most relevant to date published literature on treatment options beyond sorafenib, reported studies, ongoing investigational efforts, and possibilities for future studies in advanced hepatocellular carcinoma.

The Challenges of Modeling Drug Resistance to Antiangiogenic Therapy

Drug resistance remains an ongoing challenge for the majority of patients treated with inhibitors of the vascular endothelial growth factor (VEGF) pathway, a key regulator of tumor angiogenesis. Preclinical models have played a significant role in identifying multiple complex mechanisms of antiangiogenic treatment failure. Yet questions remain about the optimal methodology to study resistance that may assist in making clinically relevant choices about alternative or combination treatment strategies. The origins of antiangiogenic treatment failure may stem from the tumor vasculature, the tumor itself, or both together, and preclinical methods that define resistance are diverse and rarely compared. We performed a literature search of the preclinical methodologies used to examine resistance to VEGF pathway inhibitors and identified 109 papers from more than 400 that use treatment failure as the starting point for mechanistic study. We found that definitions of resistance are broad and inconsistent, involve only a small number of reagents, and derive mostly from in vitro and in vivo methodologies that often do not represent clinically relevant disease stages or progression. Together, this literature analysis highlights the challenges of studying inhibitors of the tumor microenvironment in the preclinical setting and the need for improved methodology to assist in qualifying (and quantifying) treatment failure to identify mechanisms that will help predict alternative strategies in patients.

New Directions in Anti-Angiogenic Therapy for Glioblastoma

Anti-angiogenic therapy has become an important component in the treatment of many solid tumors given the importance of adequate blood supply for tumor growth and metastasis. Despite promising preclinical data and early clinical trials, anti-angiogenic agents have failed to show a survival benefit in randomized controlled trials of patients with glioblastoma. In particular, agents targeting vascular endothelial growth factor (VEGF) appear to prolong progression free survival, possibly improve quality of life, and decrease steroid usage, yet the trials to date have demonstrated no extension of overall survival. In order to improve duration of response and convey a survival benefit, additional research is still needed to explore alternative pro-angiogenic pathways, mechanisms of resistance, combination strategies, and biomarkers to predict therapeutic response.

Sunitinib Treatment Enhances Metastasis of Innately Drug-Resistant Breast Tumors

Antiangiogenic therapies have failed to confer survival benefits in patients with metastatic breast cancer (mBC). However, to date, there has not been an inquiry into the roles for acquired versus innate drug resistance in this setting. In this study, we report roles for these distinct phenotypes in determining therapeutic response in a murine model of mBC resistance to the antiangiogenic tyrosine kinase inhibitor sunitinib. Using tumor measurement and vascular patterning approaches, we differentiated tumors displaying innate versus acquired resistance. Bioluminescent imaging of tumor metastases to the liver, lungs, and spleen revealed that sunitinib administration enhances metastasis, but only in tumors displaying innate resistance to therapy. Transcriptomic analysis of tumors displaying acquired versus innate resistance allowed the identification of specific biomarkers, many of which have a role in angiogenesis. In particular, aquaporin-1 upregulation occurred in acquired resistance, mTOR in innate resistance, and pleiotrophin in both settings, suggesting their utility as candidate diagnostics to predict drug response or to design tactics to circumvent resistance. Our results unravel specific features of antiangiogenic resistance, with potential therapeutic implications. Cancer Res; 77(4); 1008-20. ©2016 AACR.

Impact of CTLA-4 blockade in conjunction with metronomic chemotherapy on preclinical breast cancer growth

Background:

Although there are reports that metronomic cyclophosphamide (CTX) can be immune stimulating, the impact of its combination with anti-CTLA-4 immunotherapy for the treatment of cancer remains to be evaluated.

Methods:

Murine EMT-6/P breast cancer, or its cisplatin or CTX-resistant variants, or CT-26 colon, were implanted into Balb/c mice. Established tumours were monitored for relative growth following treatment with anti-CTLA-4 antibody alone or in combination with; (a) metronomic CTX (ldCTX; 20 mg kg⁻¹ day⁻¹), b) bolus (150 mg kg⁻¹) plus ldCTX, or (c) sequential treatment with gemcitabine (160 mg kg⁻¹ every 3 days).

Results:

EMT-6/P tumours responded to anti-CTLA-4 therapy, but this response was less effective when combined with bolus plus ldCTX. Anti-CTLA-4 could be effectively combined with either ldCTX (without a bolus), or with regimens of either sequential or concomitant gemcitabine, including in orthotopic EMT-6 tumours, and independently of the schedule of drug administration. Tumour responses were confirmed with CT-26 tumours but were less pronounced in drug-resistant EMT-6/CTX or EMT-6/DDP tumour models than in the parent tumour. A number of tumour bearing mice developed spontaneous metastases under continuous therapy. The majority of cured mice rejected tumour re-challenges.

Conclusions:

Metronomic CTX can be combined with anti-CTLA-4 therapy, but this therapy is impaired by concomitant bolus CTX. Sequential therapy of anti-CTLA-4 followed by gemcitabine is effective in chemotherapy-naive tumours, although tumour relapses can occur, in some cases accompanied by the development of spontaneous metastases.

Co-option of Liver Vessels and Not Sprouting Angiogenesis Drives Acquired Sorafenib Resistance in Hepatocellular Carcinoma

BACKGROUND

The anti-angiogenic Sorafenib is the only approved systemic therapy for advanced hepatocellular carcinoma (HCC). However, acquired resistance limits its efficacy. An emerging theory to explain intrinsic resistance to other anti-angiogenic drugs is 'vessel co-option,' ie, the ability of tumors to hijack the existing vasculature in organs such as the lungs or liver, thus limiting the need for sprouting angiogenesis. Vessel co-option has not been evaluated as a potential mechanism for acquired resistance to anti-angiogenic agents.

METHODS

To study sorafenib resistance mechanisms, we used an orthotopic human HCC model (n = 4-11 per group), where tumor cells are tagged with a secreted protein biomarker to monitor disease burden and response to therapy. Histopathology, vessel perfusion assessed by contrast-enhanced ultrasound, and miRNA sequencing and quantitative real-time polymerase chain reaction were used to monitor changes in tumor biology.

RESULTS

While sorafenib initially inhibited angiogenesis and stabilized tumor growth, no angiogenic 'rebound' effect was observed during development of resistance unless therapy was stopped. Instead, resistant tumors became more locally infiltrative, which facilitated extensive incorporation of liver parenchyma and the co-option of liver-associated vessels. Up to 75% (±10.9%) of total vessels were provided by vessel co-option in resistant tumors relative to 23.3% (±10.3%) in untreated controls. miRNA sequencing implicated pro-invasive signaling and epithelial-to-mesenchymal-like transition during resistance development while functional imaging further supported a shift from angiogenesis to vessel co-option.

CONCLUSIONS

This is the first documentation of vessel co-option as a mechanism of acquired resistance to anti-angiogenic therapy and could have important implications including the potential therapeutic benefits of targeting vessel co-option in conjunction with vascular endothelial growth factor receptor signaling.

Antiangiogenic therapy in oncology: current status and future directions

Angiogenesis, the formation of new blood vessels from pre-existing vessels, has been validated as a target in several tumour types through randomised trials, incorporating vascular endothelial growth factor (VEGF) pathway inhibitors into the therapeutic armoury. Although some tumours such as renal cell carcinoma, ovarian and cervical cancers, and pancreatic neuroendocrine tumours are sensitive to these drugs, others such as prostate cancer, pancreatic adenocarcinoma, and melanoma are resistant. Even when drugs have yielded significant results, improvements in progression-free survival, and, in some cases, overall survival, are modest. Thus, a crucial issue in development of these drugs is the search for predictive biomarkers-tests that predict which patients will, and will not, benefit before initiation of therapy. Development of biomarkers is important because of the need to balance efficacy, toxicity, and cost. Novel combinations of these drugs with other antiangiogenics or other classes of drugs are being developed, and the appreciation that these drugs have immunomodulatory and other modes of action will lead to combination regimens that capitalise on these newly understood mechanisms.

A Decade of Experience in Developing Preclinical Models of Advanced- or Early-Stage Spontaneous Metastasis to Study Antiangiogenic Drugs, Metronomic Chemotherapy, and the Tumor Microenvironment

The clinical circumstance of treating spontaneous metastatic disease, after resection of primary tumors, whether advanced/overt or microscopic in nature, is seldom modeled in mice and may be a major factor in explaining the frequent discordance between preclinical and clinical therapeutic outcomes where the trend is "overprediction" of positive results in preclinical mouse model studies. To evaluate this hypothesis, a research program was initiated a decade ago to develop multiple models of metastasis in mice, using variants of human tumor cell lines selected in vivo for enhanced spontaneous metastatic aggressiveness after surgical resection of established orthotopic primary tumors. These models have included breast, renal, and colorectal carcinomas; ovarian cancer (but without prior surgery); and malignant melanoma. They have been used primarily for experimental therapeutic investigations involving various antiangiogenic drugs alone or with chemotherapy, especially "metronomic" low-dose chemotherapy. The various translational studies undertaken have revealed a number of clinically relevant findings. These include the following: (i) the potential of metronomic chemotherapy, especially when combined with a vascular endothelial growth factor pathway targeting drug to successfully treat advanced metastatic disease; (ii) the development of relapsed spontaneous brain metastases in mice with melanoma or breast cancer whose systemic metastatic disease is successfully controlled for a period with a given therapy; (iii) foreshadowing the failure of adjuvant antiangiogenic drug-based phase III trials; (iv) recapitulating the failure of oral antiangiogenic tyrosine kinase inhibitors plus standard chemotherapy in contrast to the modest successes of antiangiogenic antibodies plus chemotherapy in metastatic breast cancer; and (v) revealing "vessel co-option" and absence of angiogenesis as a determinant of intrinsic resistance or minimal responsiveness to antiangiogenic therapy in lung metastases. Developing similar models of metastatic disease but involving mouse tumors grown in syngeneic immunocompetent mice may also prove useful for future translational studies of immune therapy-based treatments.

Effects of Sorafenib Dose on Acquired Reversible Resistance and Toxicity in Hepatocellular Carcinoma

Acquired evasive resistance is a major limitation of hepatocellular carcinoma (HCC) treatment with the tyrosine kinase inhibitor (TKI) sorafenib. Recent findings suggest that resistance to sorafenib may have a reversible phenotype. In addition, loss of responsiveness has been proposed to be due to a gradual decrease in sorafenib plasma levels in patients. Here, the possible mechanisms underlying reversible sorafenib resistance were investigated using a Hep3B-hCG orthotopic human xenograft model of locally advanced HCC. Tissue and plasma sorafenib and metabolite levels, downstream antitumor targets, and toxicity were assessed during standard and dose-escalated sorafenib treatment. Drug levels were found to decline significantly over time in mice treated with 30 mg/kg sorafenib, coinciding with the onset of resistance but a greater magnitude of change was observed in tissues compared with plasma. Skin rash also correlated with drug levels and tended to decrease in severity over time. Drug level changes appeared to be partially tumor dependent involving induction of tumoral CYP3A4 metabolism, with host pretreatment alone unable to generate resistance. Escalation from 30 to 60 mg/kg sorafenib improved antitumor efficacy but worsened survival due to excessive body weight loss. Microvessel density was inhibited by sorafenib treatment but remained suppressed over time and dose increase. In conclusion, tumor CYP3A4 induction by sorafenib is a novel mechanism to account for variability in systemic drug levels; however, declining systemic sorafenib levels may only be a minor resistance mechanism. Escalating the dose may be an effective treatment strategy, provided toxicity can be controlled.

Two repeated low doses of doxorubicin are more effective than a single high dose against tumors overexpressing P-glycoprotein

Standard chemotherapeutic protocols, based on maximum tolerated doses, do not prevent nor overcome chemoresistance caused by the efflux transporter P-glycoprotein (Pgp). We compared the effects of two consecutive low doses versus a single high dose of doxorubicin in drug-sensitive Pgp-negative and drug-resistant Pgp-positive human and murine cancer cells. Two consecutive low doses were significantly more cytotoxic in vitro and in vivo against drug-resistant tumors, while a single high dose failed to do so. The greater efficacy of two consecutive low doses of doxorubicin could be linked to increased levels of intracellular reactive oxygen species. These levels were produced by high electron flux from complex I to complex III of the mitochondrial respiratory chain, unrelated to the synthesis of ATP. This process induced mitochondrial oxidative damage, loss of mitochondrial potential and activation of the cytochrome c/caspase 9/caspase 3 pro-apoptotic axis in drug-resistant cells. Our work shows that the "apparent" ineffectiveness of doxorubicin against drug-resistant tumors overexpressing Pgp can be overcome by changing the timing of its administration and its doses.

Mouse models of liver cancer

Hepatocellular carcinoma (HCC) is the sixth most common cancer worldwide, and the third leading cause of cancer mortality. The great majority of patients are not eligible for curative therapies, and therapeutic approaches for advanced disease show only limited efficacy. Difficulties to treat HCC are due to the heterogenous genetic alterations of HCC, profound alterations in the hepatic microenvironment, and incomplete understanding of HCC biology. Mouse models of HCC will be helpful to improve our understanding of HCC biology, the contributions of the specific pathways and genetic alterations to carcinogenesis. In addition, mouse models of HCC may contribute to elucidate the role of the tumor microenvironment, and serve as models for preclinical studies. As no single mouse model is appropriate to study all of the above, we discuss key features and limitations of commonly used models. Furthermore, we provide detailed protocols for select models, in which HCC is induced genetically, chemically or by transplantation of tumor cells.

Hypoxia modulates the activity of a series of clinically approved tyrosine kinase inhibitors

BACKGROUND AND PURPOSE

Hypoxia in tumours is known to cause resistance to conventional chemotherapeutic drugs. In contrast, little is known about the effects of hypoxia on targeted anti-cancer drugs. This study evaluated the effect of hypoxia on a series of clinically approved tyrosine kinase inhibitors (TKIs).

EXPERIMENTAL APPROACH

The effect of hypoxia (0.1% oxygen) on the activity of conventional cytotoxic drugs (5-fluorouracil, doxorubicin and vinblastine), the hypoxia-activated prodrug tirapazamine and 9 TKIs was determined in a panel of cell lines. Where hypoxia had a marked effect on chemosensitivity, Western blot analysis was conducted to determine the effect of hypoxia on target expression and the effect of TKIs on cell signalling response under aerobic and hypoxic conditions.

KEY RESULTS

Three patterns of chemosensitivity were observed: resistance under hypoxia, equitoxic activity against hypoxic and aerobic cells, and preferential cytotoxicity to hypoxic cells. Significant hypoxia selectivity (independent of HIF1) was observed in the case of dasatinib and this correlated with the ability of dasatinib to inhibit phosphorylation of Src at tyrosine 530. Sorafenib was significantly less effective under hypoxic conditions but resistance did not correlate with hypoxia-induced changes in Raf/MEK/ERK signalling.

CONCLUSIONS AND IMPLICATIONS

Hypoxia influences the activity of TKIs but in contrast to conventional cytotoxic drugs, preferential activity against hypoxic cells can occur. The search for hypoxia-targeted therapies has been long and fruitless and this study suggests that some clinically approved TKIs could preferentially target the hypoxic fraction of some tumour types.

SC-2001 overcomes STAT3-mediated sorafenib resistance through RFX-1/SHP-1 activation in hepatocellular carcinoma

Hepatocellular carcinoma is the fifth most common solid cancer worldwide. Sorafenib, a small multikinase inhibitor, is the only approved therapy for advanced HCC. The clinical benefit of sorafenib is offset by the acquisition of sorafenib resistance. Understanding of the molecular mechanism of STAT3 overexpression in sorafenib resistance is critical if the clinical benefits of this drug are to be improved. In this study, we explored our hypothesis that loss of RFX-1/SHP-1 and further increase of p-STAT3 as a result of sorafenib treatment induces sorafenib resistance as a cytoprotective response effect, thereby, limiting sorafenib sensitivity and efficiency. We found that knockdown of RFX-1 protected HCC cells against sorafenib-induced cell apoptosis and SHP-1 activity was required for the process. SC-2001, a molecule with similar structure to obatoclax, synergistically suppressed tumor growth when used in combination with sorafenib in vitro and overcame sorafenib resistance through up-regulating RFX-1 and SHP-1 resulting in tumor suppression and mediation of dephosphorylation of STAT3. In addition, sustained sorafenib treatment in HCC led to increased p-STAT3 which was a key mediator of sorafenib sensitivity. The combination of SC-2001 and sorafenib strongly inhibited tumor growth in both wild-type and sorafenib-resistant HCC cell bearing xenograft models. These results demonstrate that inactivation of RFX/SHP-1 induced by sustained sorafenib treatment confers sorafenib resistance to HCC through p-STAT3 up-regulation. These effects can be overcome by SC-2001 through RFX-1/SHP-1 dependent p-STAT3 suppression. In conclusion, the use of SC-2001 in combination with sorafenib may constitute a new strategy for HCC therapy.

Genetic screen identifies suppressor of morphogenesis in genitalia-1 (SMG-1) as a modulator of sorafenib resistance in hepatocellular carcinoma cell lines

Hepatocellular carcinoma (HCC) is an aggressive malignancy with a poor prognosis and a very complex dysregulated molecular etiology. Furthermore, conventional therapy thus far has had only limited success. A recently developed oral multikinase inhibitor, sorafenib, has been used to improve survival in HCC patients, however, follow‑up studies have revealed a high rate of cancer recurrence. Therefore, identification of genes involved in sorafenib resistance is urgently required. RNA interference (RNAi) is a powerful tool for performing loss-of-function genetic screens and can facilitate the identification of components of the cellular signaling pathway. This study describes the results of an unbiased genomic screening using RNAi in an HCC cell line to elucidate genes related to sorafenib non-responsiveness or resistance. A genome-wide in vitro RNA interference screen revealed the role of suppressor of morphogenesis in genitalia-1 (SMG-1) as a determinant of sorafenib resistance. The inhibition of SMG-1 reduced sorafenib sensitivity in the studied HCC cell lines. An immunohistochemical comparison of cancerous and non‑cancerous regions showed strong staining in the non‑neoplastic hepatocyte regions of HCC. SMG-1 may warrant investigation as an agent to reverse sorafenib resistance.

An inducible hepatocellular carcinoma model for preclinical evaluation of antiangiogenic therapy in adult mice

The limited availability of experimental tumor models that faithfully mimic the progression of human tumors and their response to therapy remains a major bottleneck to the clinical translation and application of novel therapeutic principles. To address this challenge in hepatocellular carcinoma (HCC), one of the deadliest and most common cancers in the world, we developed and validated an inducible model of hepatocarcinogenesis in adult mice. Tumorigenesis was triggered by intravenous adenoviral delivery of Cre recombinase in transgenic mice expressing the hepatocyte-specific albumin promoter, a loxP-flanked stop cassette, and the SV40 large T-antigen (iAST). Cre recombinase-mediated excision of the stop cassette led to a transient viral hepatitis and resulted in multinodular tumorigenesis within 5 to 8 weeks. Tumor nodules with histologic characteristics of human HCC established a functional vasculature by cooption, remodeling, and angiogenic expansion of the preexisting sinusoidal liver vasculature with increasing signs of vascular immaturity during tumor progression. Treatment of mice with sorafenib rapidly resulted in the induction of vascular regression, inhibition of tumor growth, and enhanced overall survival. Vascular regression was characterized by loss of endothelial cells leaving behind avascular type IV collagen-positive empty sleeves with remaining pericytes. Sorafenib treatment led to transcriptional changes of Igf1, Id1, and cMet over time, which may reflect the emergence of potential escape mechanisms. Taken together, our results established the iAST model of inducible hepatocarcinogenesis as a robust and versatile preclinical model to study HCC progression and validate novel therapies.

Identification of Zinc Finger, MYM-type 2 (ZMYM2) as a regulator of sorafenib resistance in hepatocellular carcinoma cell lines

BACKGROUND AND AIM

Hepatocellular carcinoma (HCC) is an aggressive malignancy with a very complex molecular process. There is no successful therapy for advanced HCC at present. Recently, sorafenib has been used as a systemic therapy to improve survival in patients with advanced HCC, but increasing reports of recurrence or non-responsiveness indicate the limitations of sorafenib as a therapeutic agent. Therefore, identification of genes involved in sorafenib resistance is important to effectively treat advanced HCC.

METHODS

We performed a genomic screening with a short-hairpin RNA library cassette on HCC cell lines to find genes relating resistance to sorafenib.

RESULTS

Zinc finger, MYM type 2 (ZMYM2) was sequenced after three successive screens in vitro as a challengeable target. The inhibition of ZMYM2 resulted in sorafenib-resistance in formerly sensitive HCC cell lines. Immunohistochemical comparison of tumor and non-tumor regions showed stronger ZMYM2 staining intensities in non-tumor regions than in tumor regions.

CONCLUSION

ZMYM2 may play an important role in sorafenib resistance.

Angiogenesis and the tumor microenvironment: vascular endothelial growth factor and beyond

Our understanding of the dynamic tumor microenvironment (TME) has improved exponentially over the last few decades. In addition to traditional cytotoxic agents, anti-cancer strategies now include numerous molecular-targeted drugs that modulate distinct elements of the TME. Angiogenesis is an underlying promoter of tumor growth, invasion, and metastases. From traditional and emerging angiogenic cytokines and their receptors to novel immune checkpoint inhibitors, regulation of the tumor microenvironment is potentially key in countering tumor progression. In this article, an overview of the architecture of the TME and the orchestration of angiogenesis within the TME is provided. Additionally, traditional and novel angiogenic targets of current interest within the TME are reviewed.

Anti-angiogenic therapy for cancer: current progress, unresolved questions and future directions

Tumours require a vascular supply to grow and can achieve this via the expression of pro-angiogenic growth factors, including members of the vascular endothelial growth factor (VEGF) family of ligands. Since one or more of the VEGF ligand family is overexpressed in most solid cancers, there was great optimism that inhibition of the VEGF pathway would represent an effective anti-angiogenic therapy for most tumour types. Encouragingly, VEGF pathway targeted drugs such as bevacizumab, sunitinib and aflibercept have shown activity in certain settings. However, inhibition of VEGF signalling is not effective in all cancers, prompting the need to further understand how the vasculature can be effectively targeted in tumours. Here we present a succinct review of the progress with VEGF-targeted therapy and the unresolved questions that exist in the field: including its use in different disease stages (metastatic, adjuvant, neoadjuvant), interactions with chemotherapy, duration and scheduling of therapy, potential predictive biomarkers and proposed mechanisms of resistance, including paradoxical effects such as enhanced tumour aggressiveness. In terms of future directions, we discuss the need to delineate further the complexities of tumour vascularisation if we are to develop more effective and personalised anti-angiogenic therapies.

Treating hepatocellular carcinoma progression following first-line sorafenib: therapeutic options and clinical observations

Despite the established efficacy of sorafenib in advanced hepatocellular carcinoma (HCC), a significant number of sorafenib-treated patients experience disease progression. Current guidelines recommend either best supportive care or clinical trial enrollment for this population. As such, there remains an unmet need for tolerable, life-prolonging strategies in the second-line setting. New information regarding the molecular pathogenesis of resistance to antiangiogenic therapy and positive post-progression experience with antiangiogenics in other tumor types has led to trials investigating the effect of continued use of sorafenib, alone or combined with other agents. Trials investigating the effect of switching from sorafenib to alternate antiangiogenic agents, phosphatidylinositol 3 kinase/AKT/mammalian target of rapamycin inhibitors, or cMet inhibitors are also underway. As these data emerge, clinicians may consider a new paradigm for managing advanced HCC. This article briefly reviews the mechanisms of disease resistance to antiangiogenic therapy as a vehicle for discussing clinical strategies to prolong survival in patients with advanced HCC that are currently employed at our institutions or are under investigation. Key ongoing trials investigating the use of molecularly targeted therapies in patients with progressive disease are also highlighted.

Drug rechallenge and treatment beyond progression--implications for drug resistance

The established dogma in oncology for managing recurrent or refractory disease dictates that therapy is changed at disease progression, because the cancer is assumed to have become drug-resistant. Drug resistance, whether pre-existing or acquired, is largely thought to be a stable and heritable process; thus, reuse of therapeutic agents that have failed is generally contraindicated. Over the past few decades, clinical evidence has suggested a role for unstable, non-heritable mechanisms of acquired drug resistance pertaining to chemotherapy and targeted agents. There are many examples of circumstances where patients respond to reintroduction of the same therapy (drug rechallenge) after a drug holiday following disease relapse or progression during therapy. Additional, albeit limited, evidence suggests that, in certain circumstances, continuing a therapy beyond disease progression can also have antitumour activity. In this Review, we describe the anticancer agents used in these treatment strategies and discuss the potential mechanisms explaining the apparent tumour re-sensitization with reintroduced or continued therapy. The extensive number of malignancies and drugs that challenge the custom of permanently switching to different drugs at each line of therapy warrants a more in-depth examination of the definitions of disease progression and drug resistance and the resulting implications for patient care.

Metronomic chemotherapy: possible clinical application in advanced hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a hypervascular highly angiogenic tumor usually associated with liver cirrhosis. Vascular endothelial growth factor plays a critical role in vascular development in HCC. In contrast to the treatment of early-stage HCC, the treatment options for advanced HCC are limited and prognosis is often poor, which contributes to this tumor type being the third leading cause of cancer-related deaths worldwide. Metronomic chemotherapy, which was originally designed to inhibit angiogenesis, involves low-dose chemotherapeutic agents administered in a frequent regular schedule with no prolonged breaks and minimizes severe toxicities. We reviewed the potential effects and impact of metronomic chemotherapy in preclinical studies with HCC models and in patients with advanced HCC, especially when combined with a molecular targeted agent. Metronomic chemotherapy involves multiple mechanisms that include antiangiogenesis and antivasculogenesis, immune stimulation by reducing regulatory T cells and inducing dendritic cell maturation, and possibly some direct tumor cell targeting effects, including the cancer stem cell subpopulation. The total number of preclinical studies with HCC models shows impressive results using metronomic chemotherapy-based protocols, especially in conjunction with molecular targeted agents. Four clinical trials and two case reports evaluating metronomic chemotherapy for HCC indicate it to be a safe and potentially useful treatment for HCC. Several preclinical and clinical HCC studies suggest that metronomic chemotherapy may become an alternative type of chemotherapy for advanced unresectable HCC and postsurgical adjuvant treatment of HCC.

Drug rechallenge and treatment beyond progression--implications for drug resistance

The established dogma in oncology for managing recurrent or refractory disease dictates that therapy is changed at disease progression, because the cancer is assumed to have become drug-resistant. Drug resistance, whether pre-existing or acquired, is largely thought to be a stable and heritable process; thus, reuse of therapeutic agents that have failed is generally contraindicated. Over the past few decades, clinical evidence has suggested a role for unstable, non-heritable mechanisms of acquired drug resistance pertaining to chemotherapy and targeted agents. There are many examples of circumstances where patients respond to reintroduction of the same therapy (drug rechallenge) after a drug holiday following disease relapse or progression during therapy. Additional, albeit limited, evidence suggests that, in certain circumstances, continuing a therapy beyond disease progression can also have antitumour activity. In this Review, we describe the anticancer agents used in these treatment strategies and discuss the potential mechanisms explaining the apparent tumour re-sensitization with reintroduced or continued therapy. The extensive number of malignancies and drugs that challenge the custom of permanently switching to different drugs at each line of therapy warrants a more in-depth examination of the definitions of disease progression and drug resistance and the resulting implications for patient care.

Overcoming intratumor heterogeneity of polygenic cancer drug resistance with improved biomarker integration

Improvements in technology and resources are helping to advance our understanding of cancer-initiating events as well as factors involved with tumor progression, adaptation, and evasion of therapy. Tumors are well known to contain diverse cell populations and intratumor heterogeneity affords neoplasms with a diverse set of biologic characteristics that can be used to evolve and adapt. Intratumor heterogeneity has emerged as a major hindrance to improving cancer patient care. Polygenic cancer drug resistance necessitates reconsidering drug designs to include polypharmacology in pursuit of novel combinatorial agents having multitarget activity to overcome the diverse and compensatory signaling pathways in which cancer cells use to survive and evade therapy. Advances will require integration of different biomarkers such as genomics and imaging to provide for more adequate elucidation of the spatially varying location, type, and extent of diverse intratumor signaling molecules to provide for a rationale-based personalized cancer medicine strategy.

Liver carcinogenesis: rodent models of hepatocarcinoma and cholangiocarcinoma

Hepatocellular carcinoma and cholangiocarcinoma are primary liver cancers, both represent a growing challenge for clinicians due to their increasing morbidity and mortality. In the last few years a number of in vivo models of hepatocellular carcinoma and cholangiocarcinoma have been developed. The study of these models is providing a significant contribution in unveiling the pathophysiology of primary liver malignancies. They are also fundamental tools to evaluate newly designed molecules to be tested as new potential therapeutic agents in a pre-clinical set. Technical aspects of each model are critical steps, and they should always be considered in order to appropriately interpret the findings of a study or its planning. The purpose of this review is to describe the technical and experimental features of the most significant rodent models, highlighting similarities or differences between the corresponding human diseases. The first part is dedicated to the discussion of models of hepatocellular carcinoma, developed using toxic agents, or through dietary or genetic manipulations. In the second we will address models of cholangiocarcinoma developed in rats or mice by toxin administration, genetic manipulation and/or bile duct incannulation or surgery. Xenograft or syngenic models are also proposed.

Suppression of AKT anti-apoptotic signaling by a novel drug candidate results in growth arrest and apoptosis of hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the third most common cause of cancer fatalities worldwide, with limited treatment options and five year survival rates of between <5 and 15%. To address this medical need, we conducted a screen of a drug-like small molecule library for HCC-selective cytotoxins. We report here the identification of a disubstituted aminothiazole termed HBF-0079, with remarkable selective toxicity for HCC-derived cell lines versus non-HCC liver lines and most other cancer lines. HBF-0079 caused irreversible growth arrest and apoptosis of the HCC lines Huh7, Hep3B, HepaRG as well as the hepatoblastoma line HepG2, with CC₅₀ values from ∼0.7−7.7 µM, while more than 45 µM was needed to achieve CC₅₀ values for the immortalized normal hepatocyte lines THLE-2 and PH5CH. Of the sixty cancer lines from the National Cancer Institute panel, only five exhibited >50% growth inhibition by HBF-0079. In Huh7 cells, HBF-0079 induced cell cycle arrest in G1 and concomitant apoptosis, and its effects were irreversible after removal of the compound. These observations corroborate a loss of AKT phosphorylation at the mTORC2-targeted residue S473, with concurrent loss of phosphorylation of the mTORC1 targets SK6 and 4EBP1 in Huh7 but not PH5CH cells. Finally, growth of Hep3B-derived tumors in a murine xenograft model was significantly repressed by the compound through either systemic or intratumoral administration of formulated HBF-0079. The potential for development of this drug candidate is discussed.

Novel antiangiogenic therapies against advanced hepatocellular carcinoma (HCC)

Angiogenesis is a cornerstone in the process of hepatocarcinogenesis. In the sorafenib era, other antiangiogenic targeted drugs, such as monoclonal antibodies and a new generation of tyrosine kinase inhibitors, have been shown in phase II trials to be safe and effective in the treatment of advanced hepatocellular carcinoma. Several currently active phase III trials are testing these drugs, both in first- and second-line settings. Strategies to overcome primary and acquired resistance to antiangiogenic therapy are urgently needed. Novel biomarkers may help in improving the efficacy of drugs targeting angiogenesis.

Water extract of Hedyotis Diffusa Willd suppresses proliferation of human HepG2 cells and potentiates the anticancer efficacy of low-dose 5-fluorouracil by inhibiting the CDK2-E2F1 pathway

Hedyotis Diffusa Willd (HDW), a Chinese herbal medicine, has been widely used as an adjuvant therapy against various cancers, including hepatocellular carcinoma (HCC). However, the underlying anticancer mechanisms are yet to be elucidated. In the present study, the anticancer effects of HDW were evaluated and the efficacy and safety of HDW combined with low-dose 5-fluorouracil (5-FU) were investigated. HepG2 cells were cultured in vitro and nude mouse xenografts were established in vivo. The proliferation of HepG2 cells was measured using the MTT method and flow cytometry. The mRNA and protein expression levels of cyclin-dependent kinase 2 (CDK2), cyclin E and E2F1 were examined using relative quantitative real-time PCR and western blot analysis, respectively. The results showed that water extract of HDW remarkably inhibited HepG2 cell proliferation in a dose-dependent manner via arrest of HepG2 cells at the G0/G1 phase and induction of S phase delay. This suppression was accompanied by a great decrease of E2F1 and CDK2 mRNA expression. In addition, HDW remarkably potentiated the anticancer effect of low-dose 5-FU in the absence of overt toxicity by downregulating the mRNA and protein levels of CDK2, cyclin E and E2F1. Our findings support the use of HDW as adjuvant therapy of chemotherapy and suggest that HDW may potentiate the efficiency of low-dose 5-FU in treating HCC.