BRaf and MEK Inhibitors Differentially Regulate Cell Fate and Microenvironment in Human Hepatocellular Carcinoma

Low-Dose Sorafenib Promotes Cancer Stem Cell Expansion and Accelerated Tumor Progression in Soft Tissue Sarcomas

The cancer stem cell (CSC) hypothesis postulates that heterogeneous human cancers harbor a population of stem-like cells which are resistant to cytotoxic therapies, thus providing a reservoir of relapse following conventional therapies like chemotherapy and radiation (RT). CSCs have been observed in multiple human cancers, and their presence has been correlated with worse clinical outcomes. Here, we sought to evaluate the impact of drug dosing of the multi-tyrosine kinase inhibitor, sorafenib, on CSC and non-CSCs in soft tissue sarcoma (STS) models, hypothesizing differential effects of sorafenib based on dose and target cell population. In vitro, human cancer cell lines and primary STS from surgical specimens were exposed to escalating doses of sorafenib to determine cell viability and expression of CSC marker aldehyde dehydrogenase (ALDH). In vivo, ALDHbright CSCs were isolated, exposed to sorafenib, and xenograft growth and survival analyses were performed. We observed that sarcoma CSCs appear to paradoxically respond to the tyrosine kinase inhibitor sorafenib at low doses with increased proliferation and stem-like function of CSCs, whereas anti-viability effects dominated at higher doses. Importantly, STS patients receiving neoadjuvant sorafenib and RT on a clinical trial (NCT00864032) showed increased CSCs post therapy, and higher ALDH scores post therapy were associated with worse metastasis-free survival. These data suggest that low-dose sorafenib may promote the CSC phenotype in STS with clinically significant effects, including increased tumor growth and higher rates of metastasis formation in sarcoma patients.

The Complexity of the Tumor Microenvironment in Hepatocellular Carcinoma and Emerging Therapeutic Developments

This review explores various aspects of the HCC TME, including both cellular and non-cellular components, to elucidate their roles in tumor development and progression. Specifically, it highlights the significance of cancer-associated fibroblasts (CAFs) and their contributions to tumor progression, angiogenesis, immune suppression, and therapeutic resistance. Moreover, this review emphasizes the role of immune cells, such as tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), and regulatory T-cells (Tregs), in shaping the immunosuppressive microenvironment that promotes tumor growth and immune evasion. Furthermore, we also focused only on the non-cellular components of the HCC TME, including the extracellular matrix (ECM) and the role of hypoxia-induced angiogenesis. Alterations in the composition of ECM and stiffness have been implicated in tumor invasion and metastasis, while hypoxia-driven angiogenesis promotes tumor growth and metastatic spread. The molecular mechanisms underlying these processes, including the activation of hypoxia-inducible factors (HIFs) and vascular endothelial growth factor (VEGF) signaling, are also discussed. In addition to elucidating the complex TME of HCC, this review focuses on emerging therapeutic strategies that target the TME. It highlights the potential of second-line treatments, such as regorafenib, cabozantinib, and ramucirumab, in improving overall survival for advanced HCC patients who have progressed on or were intolerant to first-line therapy. Furthermore, this review explores the implications of the Barcelona Clinic Liver Cancer (BCLC) staging and classification system in guiding HCC management decisions. The BCLC system, which incorporates tumor stage, liver function, and performance status, provides a framework for treatment stratification and prognosis prediction in HCC patients. The insights gained from this review contribute to the development of novel therapeutic interventions and personalized treatment approaches for HCC patients, ultimately improving clinical outcomes in this challenging disease.

Haprolid Inhibits Tumor Growth of Hepatocellular Carcinoma through Rb/E2F and Akt/mTOR Inhibition

BACKGROUND

Hepatocellular carcinoma (HCC) represents a major health burden with limited curative treatment options. There is a substantial unmet need to develop innovative approaches to impact the progression of advanced HCC. Haprolid is a novel natural component isolated from myxobacteria. Haprolid has been reported as a potent selective cytotoxin against a panel of tumor cells in recent studies including HCC cells. The aims of this study are to evaluate the antitumor effect of haprolid in HCC and to understand its underlying molecular mechanisms.

METHODS

The efficacy of haprolid was evaluated in human HCC cell lines (Huh-7, Hep3B and HepG2) and xenograft tumors (NMRI-Foxn1^nu mice with injection of Hep3B cells). Cytotoxic activity of haprolid was determined by the WST-1 and crystal violet assay. Wound healing, transwell and tumorsphere assays were performed to investigate migration and invasion of HCC cells. Apoptosis and cell-cycle distribution were measured by flow cytometry. The effects of haprolid on the Rb/E2F and Akt/mTOR pathway were examined by immunoblotting and immunohistochemistry.

RESULTS

haprolid treatment significantly inhibited cell proliferation, migration and invasion in vitro. The epithelial-mesenchymal transition (EMT) was impaired by haprolid treatment and the expression level of N-cadherin, vimentin and Snail was downregulated. Moreover, growth of HCC cells in vitro was suppressed by inhibition of G1/S transition, and partially by induction of apoptosis. The drug induced downregulation of cell cycle regulatory proteins cyclin A, cyclin B and CDK2 and induced upregulation of p21 and p27. Further evidence showed that these effects of haprolid were associated with Rb/E2F downregulation and Akt/mTOR inhibition. Finally, in vivo nude mice experiments demonstrated significant inhibition of tumor growth upon haprolid treatment.

CONCLUSION

Our results show that haprolid inhibits the growth of HCC through dual inhibition of Rb/E2F and Akt/mTOR pathways. Therefore, haprolid might be considered as a new and promising candidate for the palliative therapy of HCC.

4E-BP1Thr46 Phosphorylation Association with Poor Prognosis in Quantitative Phosphoproteomics of Portal Vein Tumor Thrombus Revealed that 4E-BP1Thr46 Phosphorylation is Associated with Poor Prognosis in HCC

Purpose

Early formation of portal vein tumor thrombosis (PVTT) is a key characteristic of hepatocellular carcinoma (HCC) metastasis, but to date, the aetiology of PVTT in HCC metastasis is largely unknown. We aim to find highly sensitive and specific biomarkers for the prediction of HCC prognosis.

Patients and methods

We used isobaric tags for relative and absolute quantitation (iTRAQ) based quantitative phosphoproteomics approach to investigate the molecular signatures of the HCC with PVTT in primary HCC tissues, surrounding non-cancerous tissues and PVTT tissues. The different proteome profiles in three groups were investigated and might reveal different underlying molecular mechanisms.

Results

In total, we identified 1745 phosphoproteins with 2724 phosphopeptides and 4594 phosphorylation sites in three groups. Among these phosphoproteins, 80 phosphoproteins were dysregulated in PVTT/Pan group, 51 phosphoproteins were dysregulated in HCC/Pan group, and 10 phosphoproteins were dysregulated in PVTT/HCC group. Furthermore, the phosphorylation of 4E-BP1 was elevated in HCC tissues and PVTT tissues in comparison with surrounding non-cancerous tissues,  and the elevated fold change of phosphorylation level was higher than that in expression level of 4E-BP1. The further IHC analysis in acohort of 20 HCC tissues showed that the phosphorylation of 4E-BP1 on Thr46 might be closely related to HCC prognosis.

Conclusion

The high phosphorylation level of 4E-BP1^Thr46 might serve as a biomarker for the diagnosis of early recurrence and metastasis of HCC.

Role of BRAF in Hepatocellular Carcinoma: A Rationale for Future Targeted Cancer Therapies

The few therapeutic strategies for advance hepatocellular carcinoma (HCC) on poor knowledge of its biology. For several years, sorafenib, a tyrosine kinase inhibitors (TKI) inhibitor, has been the approved treatment option, to date, for advanced HCC patients. Its activity is the inhibition of the retrovirus-associated DNA sequences protein (RAS)/Rapidly Accelerated Fibrosarcoma protein (RAF)/mitogen-activated and extracellular-signal regulated kinase (MEK)/extracellular-signal regulated kinases (ERK) signaling pathway. However, the efficacy of sorafenib is limited by the development of drug resistance, and the major neuronal isoform of RAF, BRAF and MEK pathways play a critical and central role in HCC escape from TKIs activity. Advanced HCC patients with a BRAF mutation display a multifocal and/or more aggressive behavior with resistance to TKI. Moreover, also long non-coding RNA (lnc-RNA) have been studied in epigenetic studies for BRAF aggressiveness in HCC. So far, lnc-RNA of BRAF could be another mechanism of cancer proliferation and TKI escape in HCC and the inhibition could become a possible strategy treatment for HCC. Moreover, recent preclinical studies and clinical trials evidence that combined treatments, involving alternative pathways, have an important role of therapy for HCC and they could bypass resistance to the following TKIs: MEK, ERKs/ribosomal protein S6 kinase 2 (RSK2), and phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR). These initial data must be confirmed in clinical studies, which are currently ongoing. Translational research discoveries could create new strategies of targeted therapy combinations, including BRAF pathway, and they could eventually bring light in new treatment of HCC.

ANXA2Tyr23 and FLNASer2152 phosphorylation associate with poor prognosis in hepatic carcinoma revealed by quantitative phosphoproteomics analysis

Hepatoma is one of the most common malignant tumors, and most patients have very poor prognosis. Early prediction and intervention of the hepatoma recurrence/metastasis are the most effective way to improve the patients' clinical outcomes. Here, we used isobaric tags for relative and absolute quantitation (iTRAQ) based quantitative phospho-proteomics approach to identify biomarkers associated with hepatoma recurrence/metastasis in hepatoma cell lines with increasing metastasis ability. In total, 75 phosphorylated peptides corresponding to 60 phosphoproteins were significantly dysregulated and the participated biological processes of these phosphoproteins were tightly associated with tumor metastasis. Further signaling pathway analysis revealed that key signaling pathways which play crucial roles in cancer metastasis have been significantly over activated in the highly metastatic cells. Furthermore, the phosphorylation of FLNA^Ser2152 and ANXA2^Tyr23 were validated to be significantly up regulated in the high-metastatic cells comparing with the low-metastatic cells. By further investigation the clinical significance of the phosphorylation of FLNA^Ser2152 and ANXA2^Tyr23 in large-scale clinical samples, revealed that the over phosphorylation of FLNA^Ser2152 and ANXA2^Tyr23 were associated with poor prognosis and might be potential prognostic biomarkers for the primary hepatoma. When FLNA^Ser2152 combined with ANXA2^Tyr23, it had a better prognostic value for both OS and TTR.

TGFβ1 regulates HGF-induced cell migration and hepatocyte growth factor receptor MET expression via C-ets-1 and miR-128-3p in basal-like breast cancer

Breast cancer is the most common cancer in women worldwide. The tumor microenvironment contributes to tumor progression by inducing cell dissemination from the primary tumor and metastasis. TGFβ signaling is involved in breast cancer progression and is specifically elevated during metastatic transformation in aggressive breast cancer. In this study, we performed genomewide correlation analysis of TGFBR2 expression in a panel of 51 breast cancer cell lines and identified that MET is coregulated with TGFBR2. This correlation was confirmed at the protein level in breast cancer cell lines and human tumor tissues. Flow cytometric analysis of luminal and basal‐like breast cancer cell lines and examination of 801 tumor specimens from a prospective cohort of breast cancer patients using reverse phase protein arrays revealed that expression of TGFBR2 and MET is increased in basal‐like breast cancer cell lines, as well as in triple‐negative breast cancer tumor tissues, compared to other subtypes. Using real‐time cell analysis technology, we demonstrated that TGFβ1 triggered hepatocyte growth factor (HGF)‐induced and MET‐dependent migration in vitro. Bioinformatic analysis predicted that TGFβ1 induces expression of C‐ets‐1 as a candidate transcription factor regulating MET expression. Indeed, TGFβ1‐induced expression of ETS1 and breast cancer cell migration was blocked by knockdown of ETS1. Further, we identified that MET is a direct target of miR‐128‐3p and that this miRNA is negatively regulated by TGFβ1. Overexpression of miR‐128‐3p reduced MET expression and abrogated HGF‐induced cell migration of invasive breast cancer cells. In conclusion, we have identified that TGFβ1 regulates HGF‐induced and MET‐mediated cell migration, through positive regulation of C‐ets‐1 and negative regulation of miR‐128‐3p expression in basal‐like breast cancer cell lines and in triple‐negative breast cancer tissue.

Probing DNA Hybridization Equilibrium by Cationic Conjugated Polymer for Highly Selective Detection and Imaging of Single-Nucleotide Mutation

Hybridization-based probes emerge as a promising tool for nucleic acid target detection and imaging. However, the single-nucleotide selectivity is still challenging because the specificity of hybridization reaction is typically low at room temperature. We disclose an effective and simple method for highly selective detection and in situ imaging of single-nucleotide mutation (SNM) by taking the advantages of the specific hybridization of short duplex and the signal amplifying effect of cationic conjugated polymer (CCP). Excellent discrimination of the nucleic acid strands only differing by single nucleotide was achieved enabling the sensitive detection of SNM at the abundance as low as 0.1%. Single-molecule fluorescence resonance energy transfer (smFRET) study reveals that the presence of CCP enhances the perfect matched duplex and the mismatched duplex to a different extent, which can be an explanation for the high single-nucleotide selectivity. Due to the simple design of the probe and the stable brightness of CCP, highly selective mRNA in situ imaging was achieved in fixed cells. Melanoma cell line A375 with BRAF V600E point mutation exhibits higher FRET efficiency than liver cancer cell line HegG2 that was not reported having the mutation at this point.

pH regulators to target the tumor immune microenvironment in human hepatocellular carcinoma

Interfering with tumor metabolism is an emerging strategy for treating cancers that are resistant to standard therapies. Featuring a rapid proliferation rate and exacerbated glycolysis, hepatocellular carcinoma (HCC) creates a highly hypoxic microenvironment with excessive production of lactic and carbonic acids. These metabolic conditions promote disease aggressiveness and cancer-related immunosuppression. The pH regulatory molecules work as a bridge between tumor cells and their surrounding milieu. Herein, we show that the pH regulatory molecules CAIX, CAXII and V-ATPase are overexpressed in the HCC microenvironment and that interfering with their pathways exerts antitumor activity. Importantly, the V-ATPase complex was expressed by M2-like tumor-associated macrophages. Blocking ex vivo V-ATPase activity established a less immune-suppressive tumor microenvironment and reversed the mesenchymal features of HCC. Thus, targeting the unique cross-talk between tumor cells and the tumor microenvironment played by pH regulatory molecules holds promise as a strategy to control HCC progression and to reduce the immunosuppressive pressure mediated by the hypoxic/acidic metabolism, particularly considering the potential combination of this strategy with emerging immune checkpoint-based immunotherapies.

MicroRNA-519a-3p mediates apoptosis resistance in breast cancer cells and their escape from recognition by natural killer cells

Aggressive breast cancer is associated with poor patient outcome and characterized by the development of tumor cell variants that are able to escape from control of the immune system or are resistant to targeted therapies. The complex molecular mechanisms leading to immune escape and therapy resistance are incompletely understood. We have previously shown that high miR-519a-3p levels are associated with poor survival in breast cancer. Here, we demonstrate that miR-519a-3p confers resistance to apoptosis induced by TRAIL, FasL and granzyme B/perforin by interfering with apoptosis signaling in breast cancer cells. MiR-519a-3p diminished the expression of its direct target genes for TRAIL-R2 (TNFRSF10B) and for caspase-8 (CASP8) and its indirect target gene for caspase-7 (CASP7), resulting in reduced sensitivity and tumor cell apoptosis in response to apoptotic stimuli. Furthermore, miR-519a-3p impaired tumor cell killing by natural killer (NK) cells via downregulation of the NKG2D ligands ULBP2 and MICA on the surface of tumor cells that are crucial for the recognition of these tumor cells by NK cells. We determined that miR-519a-3p was overexpressed in more aggressive mutant TP53 breast cancer that was associated with poor survival. Furthermore, low levels of TRAIL-R2, caspase-7 and caspase-8 correlated with poor survival, suggesting that the inhibitory effect of miR-519a-3p on TRAIL-R2 and caspases may have direct clinical relevance in lowering patient’s prognosis. In conclusion, we demonstrate that miR-519a-3p is a critical factor in mediating resistance toward cancer cell apoptosis and impairing tumor cell recognition by NK cells. This joint regulation of apoptosis and immune cell recognition through miR-519a-3p supports the hypothesis that miRNAs are key regulators of cancer cell fate, facilitating cancer progression and evasion from immunosurveillance at multiple and interconnected levels.

Inhibition of RAF1 kinase activity restores apicobasal polarity and impairs tumour growth in human colorectal cancer

BACKGROUND AND AIM

Colorectal cancer (CRC) remains one of the leading causes of cancer-related death. Novel therapeutics are urgently needed, especially for tumours with activating mutations in KRAS (∼40%). Here we investigated the role of RAF1 in CRC, as a potential, novel target.

METHODS

Colonosphere cultures were established from human tumour specimens obtained from patients who underwent colon or liver resection for primary or metastatic adenocarcinoma. The role of RAF1 was tested by generating knockdowns (KDs) using three independent shRNA constructs or by using RAF1-kinase inhibitor GW5074. Clone-initiating and tumour-initiating capacities were assessed by single-cell cloning and injecting CRC cells into immune-deficient mice. Expression of tight junction (TJ) proteins, localisation of polarity proteins and activation of MEK-ERK pathway was analysed by western blot, immunohistochemistry and immunofluorescence.

RESULTS

KD or pharmacological inhibition of RAF1 significantly decreased clone-forming and tumour-forming capacity of all CRC cultures tested, including KRAS-mutants. This was not due to cytotoxicity but, at least in part, to differentiation of tumour cells into goblet-like cells. Inhibition of RAF1-kinase activity restored apicobasal polarity and the formation of TJs in vitro and in vivo, without reducing MEK-ERK phosphorylation. MEK-inhibition failed to restore polarity and TJs. Moreover, RAF1-impaired tumours were characterised by normalised tissue architecture.

CONCLUSIONS

RAF1 plays a critical role in maintaining the transformed phenotype of CRC cells, including those with mutated KRAS. The effects of RAF1 are kinase-dependent, but MEK-independent. Despite the lack of activating mutations in RAF1, its kinase domain is an attractive therapeutic target for CRC.

Genome-Wide CRISPR Screen Identifies Regulators of Mitogen-Activated Protein Kinase as Suppressors of Liver Tumors in Mice

BACKGROUND & AIMS

It has been a challenge to identify liver tumor suppressors or oncogenes due to the genetic heterogeneity of these tumors. We performed a genome-wide screen to identify suppressors of liver tumor formation in mice, using CRISPR-mediated genome editing.

METHODS

We performed a genome-wide CRISPR/Cas9-based knockout screen of P53-null mouse embryonic liver progenitor cells that overexpressed MYC. We infected p53-/-;Myc;Cas9 hepatocytes with the mGeCKOa lentiviral library of 67,000 single-guide RNAs (sgRNAs), targeting 20,611 mouse genes, and transplanted the transduced cells subcutaneously into nude mice. Within 1 month, all the mice that received the sgRNA library developed subcutaneous tumors. We performed high-throughput sequencing of tumor DNA and identified sgRNAs increased at least 8-fold compared to the initial cell pool. To validate the top 10 candidate tumor suppressors from this screen, we collected data from patients with hepatocellular carcinoma (HCC) using the Cancer Genome Atlas and COSMIC databases. We used CRISPR to inactivate candidate tumor suppressor genes in p53-/-;Myc;Cas9 cells and transplanted them subcutaneously into nude mice; tumor formation was monitored and tumors were analyzed by histology and immunohistochemistry. Mice with liver-specific disruption of p53 were given hydrodynamic tail-vein injections of plasmids encoding Myc and sgRNA/Cas9 designed to disrupt candidate tumor suppressors; growth of tumors and metastases was monitored. We compared gene expression profiles of liver cells with vs without tumor suppressor gene disrupted by sgRNA/Cas9. Genes found to be up-regulated after tumor suppressor loss were examined in liver cancer cell lines; their expression was knocked down using small hairpin RNAs, and tumor growth was examined in nude mice. Effects of the MEK inhibitors AZD6244, U0126, and trametinib, or the multi-kinase inhibitor sorafenib, were examined in human and mouse HCC cell lines.

RESULTS

We identified 4 candidate liver tumor suppressor genes not previously associated with liver cancer (Nf1, Plxnb1, Flrt2, and B9d1). CRISPR-mediated knockout of Nf1, a negative regulator of RAS, accelerated liver tumor formation in mice. Loss of Nf1 or activation of RAS up-regulated the liver progenitor cell markers HMGA2 and SOX9. RAS pathway inhibitors suppressed the activation of the Hmga2 and Sox9 genes that resulted from loss of Nf1 or oncogenic activation of RAS. Knockdown of HMGA2 delayed formation of xenograft tumors from cells that expressed oncogenic RAS. In human HCCs, low levels of NF1 messenger RNA or high levels of HMGA2 messenger RNA were associated with shorter patient survival time. Liver cancer cells with inactivation of Plxnb1, Flrt2, and B9d1 formed more tumors in mice and had increased levels of mitogen-activated protein kinase phosphorylation.

CONCLUSIONS

Using a CRISPR-based strategy, we identified Nf1, Plxnb1, Flrt2, and B9d1 as suppressors of liver tumor formation. We validated the observation that RAS signaling, via mitogen-activated protein kinase, contributes to formation of liver tumors in mice. We associated decreased levels of NF1 and increased levels of its downstream protein HMGA2 with survival times of patients with HCC. Strategies to inhibit or reduce HMGA2 might be developed to treat patients with liver cancer.

MEK 1/2 inhibitors in the treatment of hepatocellular carcinoma

Sorafenib is the only approved systemic treatment for advanced hepatocellular carcinoma patients and all the recently published randomized controlled trials on new systemic drugs have been unsuccessful. This is likely due to a lack of understanding of tumor progression, molecular drivers, and liver toxicity, as well as flaws in trial design. An important signaling pathway in hepatocarcinogenesis is the MEK cascade involved in various cellular responses, including adaptation and survival. A key role in this cascade is played by MEK, of which MEK 1/2 represent the prototypes and an interesting target for new oncological drugs. This review analyzes recent developments and future perspectives on the role of MEK inhibitors in hepatocellular carcinoma treatment.

Hepatocellular carcinoma: Where there is unmet need

Hepatocellular carcinoma (HCC) is a complex and heterogeneous tumor most commonly associated with underlying chronic liver disease, especially hepatitis. It is a growing problem in the United States and worldwide. There are two potential ways to prevent HCC. Primary prevention which is based on vaccination or secondary prevention involving agents that slow down carcinogenesis. Several pathways have been thought to play a role in the development of HCC; specifically, those involving vascular endothelial growth factor (VEGF)-mediated angiogenesis, WNT, phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR), AMP-activated protein kinase (AMPK), and c-MET. Currently, there are only a limited number of drugs which have been proven as effective treatment options for HCC and several clinical trials are testing drugs which target aberrations in the pathways mentioned above. In this review, we discuss currently approved therapies, monotherapies and combination therapy for the treatment of HCC.