Regorafenib inhibits colorectal tumor growth through PUMA-mediated apoptosis

Depletion of oxysterol-binding proteins by OSW-1 triggers RIP1/RIP3-independent necroptosis and sensitization to cancer immunotherapy

Oxysterol-binding proteins (OSBPs), lipid transfer proteins functioning at intracellular membrane contact sites, are recently found to be dysregulated in cancer and promote cancer cell survival. However, their role as potential targets in cancer therapy remains largely unexplored. In this study, we found OSW-1, a natural compound and OSBP inhibitor, potently and selectively kills colon cancer cells by activating a previously unknown necroptosis pathway that is independent of receptor-interacting protein 1 (RIP1) and RIP3. OSW-1 stabilizes p53 and degrades OSBPs to promote endoplasmic reticulum (ER) stress and glycogen synthase kinase 3β (GSK3β)/Tip60-mediated p53 acetylation at Lysine 120, which selectively induces its target PUMA. PUMA-mediated mitochondrial calcium influx activates calcium/calmodulin-dependent protein kinase IIδ (CamKIIδ) to promote mixed lineage kinase domain-like (MLKL) phosphorylation and necroptotic cell death. Furthermore, OSW-1-induced necroptosis is highly immunogenic and sensitizes syngeneic colorectal tumors to anti-PD-1 immunotherapy. Together, our results identified a novel RIP1/RIP3-independent necroptosis pathway underlying the extremely potent anticancer activity of OSW-1, which can be harnessed to develop new anticancer therapies by selectively stimulating antitumor immunity.

Enhancing Colorectal Cancer Treatment Through VEGF/VEGFR Inhibitors and Immunotherapy

OPINION STATEMENT

Colorectal cancer, ranking as the third most prevalent malignancy globally, substantially benefits from both immunotherapy and VEGF/VEGFR inhibitors. Nevertheless, the use of monotherapy proves inadequate in effectively tackling the heterogeneity of tumors and the intricacies of their microenvironment, frequently leading to drug resistance and immune evasion. This situation underscores the pressing need for innovative strategies aimed at augmenting the effectiveness and durability of treatments. Clinical research demonstrates that the combination of VEGF/VEGFR inhibitors (primarily including VEGF/VEGFR-targeted drugs and multi-kinase inhibitors) with immune checkpoint inhibitors creates a synergistic effect in the treatment of colorectal cancer. Our analysis explores how VEGF/VEGFR inhibitors recalibrate the tumor microenvironment, modulate immune cell functions, and influence the expression of immune checkpoints and cytokines. Furthermore, we critically evaluate the preclinical and clinical feasibility of these combined therapeutic approaches. Despite the potential for toxicity, the significant benefits and prospective applications of these strategies warrant thorough exploration. Exploring the synergistic mechanisms of these combined treatments has the potential to inaugurate a new paradigm in oncology, enabling more personalized and efficacious treatment modalities. Additionally, the synergy between VEGF/VEGFR inhibitors and nascent immunotherapies emerges as a promising field of inquiry.

Personalized medicine in colorectal cancer: a comprehensive study of precision diagnosis and treatment

Colorectal cancer is a common and fatal disease that affects many people globally. CRC is classified as the third most prevalent cancer among males and the second most frequent cancer among females worldwide. The purpose of this article is to examine how personalized medicine might be used to treat colorectal cancer. The classification of colorectal cancer based on molecular profiling, including the detection of significant gene mutations, genomic instability, and gene dysregulation, is the main topic of this discussion. Advanced technologies and biomarkers are among the detection methods that are explored, demonstrating their potential for early diagnosis and precise prognosis. In addition, the essay explores the world of treatment possibilities by providing light on FDA-approved personalized medicine solutions that provide individualized and precise interventions based on patient characteristics. This article assesses targeted treatments like cetuximab and nivolumab, looks at the therapeutic usefulness of biomarkers like microsatellite instability (MSI) and circulating tumor DNA (ctDNA), and investigates new approaches to combat resistance. Through this, our review provides a thorough overview of personalized medicine in the context of colorectal cancer, ultimately highlighting its potential to revolutionize the field and improve patient care.

Regorafenib with or without chemotherapy/immunotherapy in second-line treatment of metastatic colorectal cancer during the COVID-19 pandemic: a single-center retrospective analysis

Background

Regorafenib, approved in China for the third-line treatment of patients with metastatic colorectal cancer (mCRC), targets multiple tyrosine kinases. We retrospectively evaluated the efficacy and safety of regorafenib, both as monotherapy and in combination with capecitabine or immune checkpoint inhibitors (ICIs), as a second-line treatment for patients unable to access hospital-based care due to limited hospital visits during the coronavirus disease 2019 (COVID-19) pandemic.

Methods

Retrospective analysis was conducted on individual patient data from Peking University Third Hospital, covering the period from January 2020 to September 2023. The primary endpoint was progression-free survival (PFS), with secondary endpoints including overall survival (OS) and safety.

Results

The study comprised 31 patients with a median age of 65 years. The median PFS (mPFS) was 6.0 months, while the median OS (mOS) was 20.0 months. Compared to those treated with regorafenib alone, patients treated with regorafenib plus capecitabine/ICIs tended to have a longer PFS (8.0 vs. 4.0 months) and OS (27.0 vs. 15.0 months). Liver metastases [hazard ratio (HR) =2.515, 95% confidence interval (CI): 1.037-6.100; P=0.04] and prior bevacizumab treatment (HR =2.613, 95% CI: 1.168-5.846; P=0.02) were identified as independent prognostic factors for PFS. Frequent grade 3/4 adverse drug reactions (ADRs) included hand-foot skin reactions (HFSRs), fatigue, hypertension, and proteinuria.

Conclusions

This single-center, retrospective study indicates that regorafenib, alone or combined with chemotherapy/immunotherapy, is a feasible and safe second-line treatment for mCRC for situations where hospital access is limited, such as during the COVID-19 pandemic. Additional prospective studies are required to investigate the advantages of combination therapies.

Regorafenib enhances M1/M2 macrophage polarization by inhibiting the secretion of plasminogen activator inhibitor-1 in head and neck squamous cell carcinoma

AIMS

Regorafenib, an oral multikinase inhibitor, is approved for the treatment of various metastatic/advanced cancers. Although clinical trials have reported the efficacy of regorafenib in multiple cancer types, its immunomodulatory activity in head and neck squamous cell carcinoma (HNSCC) remains unclear.

MAIN METHODS

This study investigated the effects of regorafenib on tumorigenesis by using two mouse models of HNSCC. The distribution of immune cells in tumor tissues was assessed through flow cytometry, RNA sequencing, and multiplex immunofluorescence staining.

KEY FINDINGS

Regorafenib exhibited significant antitumor activity in our HNSCC mouse models. Tumor-infiltrating lymphocyte isolation and RNA sequencing revealed that regorafenib can activate immune functions. Moreover, regorafenib-treated tumor-conditioned medium regulated macrophage proliferation ex vivo. Our data suggests that regorafenib modulates immune function by regulating both tumor and immune cells. Specifically, regorafenib induced the polarization of macrophages toward the proinflammatory M1 phenotype by suppressing the production of plasminogen activator inhibitor 1 (PAI-1), a macrophage regulator. In addition, regorafenib suppressed the secretion of PAI-1 from ex vivo human HNSCC organoids.

SIGNIFICANCE

Regorafenib enhances M1/M2 macrophage polarization and suppresses PAI-1 secretion from cancer cells, leading to a shift from M2 to M1 macrophages in the HNSCC tumor microenvironment.

Osteosarcoma cells depend on MCL-1 for survival, and osteosarcoma metastases respond to MCL-1 antagonism plus regorafenib in vivo

Osteosarcoma is the most common form of primary bone cancer, which primarily afflicts children and adolescents. Chemotherapy, consisting of doxorubicin, cisplatin and methotrexate (MAP) increased the 5-year osteosarcoma survival rate from 20% to approximately 60% by the 1980s. However, osteosarcoma survival rates have remained stagnant for several decades. Patients whose disease fails to respond to MAP receive second-line treatments such as etoposide and, in more recent years, the kinase inhibitor regorafenib. BCL-2 and its close relatives enforce cellular survival and have been implicated in the development and progression of various cancer types. BH3-mimetics antagonize pro-survival members of the BCL-2 family to directly stimulate apoptosis. These drugs have been proven to be efficacious in other cancer types, but their use in osteosarcoma has been relatively unexplored to date. We investigated the potential efficacy of BH3-mimetics against osteosarcoma cells in vitro and examined their cooperation with regorafenib in vivo. We demonstrated that osteosarcoma cell lines could be killed through inhibition of MCL-1 combined with BCL-2 or BCL-xL antagonism. Inhibition of MCL-1 also sensitized osteosarcoma cells to killing by second-line osteosarcoma treatments, particularly regorafenib. Importantly, we found that inhibition of MCL-1 with the BH3-mimetic S63845 combined with regorafenib significantly prolonged the survival of mice bearing pulmonary osteosarcoma metastases. Together, our results highlight the importance of MCL-1 in osteosarcoma cell survival and present a potential therapeutic avenue that may improve metastatic osteosarcoma patient outcomes.

The Effect of Statin Usage on Survival in Metastatic Colorectal Cancer Patients Receiving Regorafenib

BACKGROUND/AIM

Regorafenib is an oral multikinase inhibitor used in later lines for metastatic colorectal carcinoma (mCRC) treatment, but its efficacy and tolerability are low. To improve the response rates and ameliorate adverse effects, different strategies have been implemented. In our study, we examined the effect of statin usage in patients with mCRC treated with regorafenib.

PATIENTS AND METHODS

This single-center retrospective study included patients with mCRC who were treated with regorafenib between January 2015 and December 2023. The primary outcomes were progression-free survival (PFS) and overall survival (OS), and the secondary outcomes were adverse effects and the tolerability of regorafenib.

RESULTS

The data of 105 patients were collected retrospectively. The median age of the patients was 66 years, and 60 patients were male. Seventeen patients (16.1%) were receiving statins. Statin-using patients were significantly older than non-users (72 years vs. 66.5 years, p=0.05). Comorbid diseases were more common in patients using statins. The median PFS was 1.9 months for statin users and 4.2 months for statin non-users (p<0.001), and the median OS was 4.7 vs. 6.7 months (p=0.01). Cox regression revealed that statin usage was significantly associated with a higher hazard ratio (HR) for PFS (2.53) and OS (2.06) (both p<0.01 and p=0.02, respectively).

CONCLUSION

Statins are associated with decreased survival and response rates in patients with mCRC treated with regorafenib. However, further studies are needed to confirm these results.

Regorafenib promotes antitumor progression in melanoma by reducing RRM2

Melanoma is a malignant tumor with a terrible prognosis. Although so many therapies are used for melanoma, the overall survival rate is still poor globally. Novel therapies are still required. In our study, the role and potential mechanism of regorafenib in melanoma are explored. Regorafenib has the ability to limit the growth, invasion, and metastasis of melanoma cells but to upregulate apoptosis-prompting markers (cleaved-PARP and Bax). RRM2 is identified to be the downstream target of regorafenib by RNA sequencing. In addition, we discovered that RRM2 inhibition and regorafenib have comparable effects on melanoma cells. Rescue experiments showed that RRM2 is crucial in regulating regorafenib's anti-melanoma progression. Moreover, ERK/E2F3 signaling influences regorafenib's ability to suppress melanoma cell growth. Ultimately, regorafenib significantly inhibits tumor growth in vivo. In conclusion, our finding demonstrated that regorafenib promotes antitumor progression in melanoma by reducing RRM2.

Metformin and buparlisib synergistically induce apoptosis of non-small lung cancer (NSCLC) cells via Akt/FoxO3a/Puma axis

Non-small cell lung cancer (NSCLC) is a global health issue lacking effective treatments. Buparlisib is a pan-PI3K inhibitor that shows promising clinical results in treating NSCLC. However, chemoresistance is inevitable and hampers the application of buparlisib. Studies show that a combination of phytochemicals and chemotherapeutics enhances its effectiveness. Here, we evaluated the role of metformin, an agent with multiple pharmacological properties, in enhancing the anti-tumour activities of buparlisib against NSCLC cells. Our results showed that metformin and buparlisib synergistically inhibited cell viability, migration, and invasion of NSCLC cells. In addition, co-treatment of metformin and buparlisib also induced cell cycle arrest and cell death in NSCLC cells. Mechanistically, metformin and buparlisib repressed Mcl-1 and upregulated Puma in NSCLC cells in a p53-independent manner. Moreover, they inhibited the PI3K/Akt signalling pathway, leading to activation of the FoxO3a/Puma signalling in NSCLC cells. Our findings suggest that combined treatment of metformin and buparlisib might provide a promising strategy for treating NSCLC.

PUMA/RIP3 Mediates Chemotherapy Response via Necroptosis and Local Immune Activation in Colorectal Cancer

Induction of programmed cell death (PCD) is a key cytotoxic effect of anticancer therapies. PCD is not confined to caspase-dependent apoptosis, but includes necroptosis, a regulated form of necrotic cell death controlled by receptor-interacting protein (RIP) kinases 1 and 3, and mixed lineage kinase domain-like (MLKL) pseudokinase. Necroptosis functions as a defense mechanism against oncogenic mutations and pathogens and can be induced by a variety of anticancer agents. However, the functional role and regulatory mechanisms of necroptosis in anticancer therapy are poorly understood. In this study, we found that RIP3-dependent but RIP1-independent necroptosis is engaged by 5-fluorouracil (5-FU) and other widely used antimetabolite drugs, and functions as a major mode of cell death in a subset of colorectal cancer cells that express RIP3. We identified a novel 5-FU-induced necroptosis pathway involving p53-mediated induction of the BH3-only Bcl-2 family protein, p53 upregulated modulator of apoptosis (PUMA), which promotes cytosolic release of mitochondrial DNA and stimulates its sensor z-DNA-binding protein 1 (ZBP1) to activate RIP3. PUMA/RIP3-dependent necroptosis mediates the in vitro and in vivo antitumor effects of 5-FU and promotes a robust antitumor immune response. Our findings provide a rationale for stimulating necroptosis to enhance tumor cell killing and antitumor immune response leading to improved colorectal cancer treatments.

Pim Kinase Inhibitors Increase Gilteritinib Cytotoxicity in FLT3-ITD Acute Myeloid Leukemia Through GSK-3β Activation and c-Myc and Mcl-1 Proteasomal Degradation

Acute myeloid leukemia (AML) with fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) has poor outcomes. FLT3-ITD drives constitutive and aberrant FLT3 signaling, activating STAT5 and upregulating the downstream oncogenic serine/threonine kinase Pim-1. FLT3 inhibitors are in clinical use, but with limited and transient efficacy. We previously showed that concurrent treatment with Pim and FLT3 inhibitors increases apoptosis induction in FLT3-ITD-expressing cells through posttranslational downregulation of Mcl-1. Here we further elucidate the mechanism of action of this dual targeting strategy. Cytotoxicity, apoptosis and protein expression and turnover were measured in FLT3-ITD-expressing cell lines and AML patient blasts treated with the FLT3 inhibitor gilteritinib and/or the Pim inhibitors AZD1208 or TP-3654. Pim inhibitor and gilteritinib cotreatment increased apoptosis induction, produced synergistic cytotoxicity, downregulated c-Myc protein expression, earlier than Mcl-1, increased turnover of both proteins, which was rescued by proteasome inhibition, and increased efficacy and prolonged survival in an in vivo model. Gilteritinib and Pim inhibitor cotreatment of Ba/F3-ITD cells infected with T58A c-Myc or S159A Mcl-1 plasmids, preventing phosphorylation at these sites, did not downregulate these proteins, increase their turnover or increase apoptosis induction. Moreover, concurrent treatment with gilteritinib and Pim inhibitors dephosphorylated (activated) the serine/threonine kinase glycogen synthase kinase-3β (GSK-3β), and GSK-3β inhibition prevented c-Myc and Mcl-1 downregulation and decreased apoptosis induction. The data are consistent with c-Myc T58 and Mcl-1 S159 phosphorylation by activated GSK-3β as the mechanism of action of gilteritinib and Pim inhibitor combination treatment, further supporting GSK-3β activation as a therapeutic strategy in FLT3-ITD AML.

SIGNIFICANCE

FLT3-ITD is present in 25% of in AML, with continued poor outcomes. Combining Pim kinase inhibitors with the FDA-approved FLT3 inhibitor gilteritinib increases cytotoxicity in vitro and in vivo through activation of GSK-3β, which phosphorylates and posttranslationally downregulates c-Myc and Mcl-1. The data support efficacy of GSK-3β activation in FLT3-ITD AML, and also support development of a clinical trial combining the Pim inhibitor TP-3654 with gilteritinib.

Regorafenib inhibits growth, survival and angiogenesis in nasopharyngeal carcinoma and is synergistic with Mcl-1 inhibitor

OBJECTIVES

Regorafenib is an oral multi-kinase inhibitor approved for various metastatic/advanced cancers, and has been investigated in clinical trials in many other tumour entities. The purpose of this study was to evaluate the therapeutic potential of regorafenib for nasopharyngeal carcinoma (NPC).

METHODS

Cellular proliferation, survival, apoptosis and colony formation assays were performed and combination index was determined. NPC xenograft tumour models were established. In vitro and In vivo angiogenesis assays were performed.

KEY FINDINGS

Regorafenib is effective against a panel of NPC cell lines regardless of cellular origin and genetic profiling while sparing normal nasal epithelial cells. The predominant inhibitory effects of regorafenib in NPC are anchorage-dependent and anchorage-independent growth rather than survival. Apart from tumour cells, regorafenib potently inhibits angiogenesis. Mechanistically, regorafenib inhibits multiple oncogenic pathways including Raf/Erk/Mek and PI3K/Akt/mTOR. Regorafenib decreases Bcl-2 but not Mcl-1 level in NPC cells. The in vitro observations are evident in in vivo NPC xenograft mouse model. The combination of Mcl-1 inhibitor with regorafenib is synergistic in inhibiting NPC growth without causing systemic toxicity in mice.

CONCLUSIONS

Our findings also support further clinical investigation of regorafenib and Mcl-1 inhibitor for NPC treatment.

Small Molecules against Metastatic Tumors: Concrete Perspectives and Shattered Dreams

Metastasis is the main cause of anti-cancer therapy failure, leading to unfavorable prognosis for patients. The true challenge to increase cancer patient life expectancy by making cancer a chronic disease with periodic but manageable relapses relies on the development of efficient therapeutic strategies specifically directed against key targets in the metastatic process. Traditional chemotherapy with classical alkylating agents, microtubule inhibitors, and antimetabolites has demonstrated its limited efficacy against metastatic cells due to their capacity to select chemo-resistant cell populations that undergo epithelial-to-mesenchymal transition (EMT), thus promoting the colonization of distant sites that, in turn, sustain the initial metastatic process. This scenario has prompted efforts aimed at discovering a wide variety of small molecules and biologics as potential anti-metastatic drugs directed against more specific targets known to be involved in the various stages of metastasis. In this short review, we give an overview of the most recent advances related to important families of antimetastatic small molecules: intracellular tyrosine kinase inhibitors, cyclin-dependent kinase inhibitors, KRAS inhibitors, and integrin antagonists. Although the majority of these small molecules are not yet approved and not available in the drug market, any information related to their stage of development could represent a precious and valuable tool to identify new targets in the endless fight against metastasis.

Chemo-radiotherapy with 177Lu-PLGA(RGF)-CXCR4L for the targeted treatment of colorectal cancer

Introduction

More than 1.9 million new cases of colorectal cancer and 935,000 deaths were estimated to have occurred worldwide in 2020. Therapies for metastatic colorectal cancer include cytotoxic chemotherapy and targeted therapies in multiple lines of treatment. Nevertheless, the optimal use of these agents has not yet been resolved. Regorafenib (RGF) is an Food and Drug Administration (FDA)-authorized multikinase inhibitor indicated for patients with metastatic colorectal cancer, non-responding to priority lines of chemotherapy and immunotherapy. Nanoparticles have been used in specific applications, such as site-specific drug delivery systems, cancer therapy, and clinical bioanalytical diagnostics. C-X-C Chemokine receptor type 4 (CXCR4) is the most widely-expressed chemokine receptor in more than 23 human cancer types, including colorectal cancer. This research aimed to synthesize and preclinically evaluate a targeted nanosystem for colorectal cancer chemo-radiotherapy using RGF encapsulated in Poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles coated with a CXCR4 ligand (CXCR4L) and 177Lu as a therapeutic β-emitter.

Methods

Empty PLGA and PLGA(RGF) nanoparticles were prepared using the microfluidic method, followed by the DOTA and CXCR4L functionalization and nanoparticle radiolabeling with 177Lu. The final nanosystem gave a particle size of 280 nm with a polydispersity index of 0.347. In vitro and in vivo toxicity effects were assessed using the HCT116 colorectal cancer cell line.

Results

177Lu-PLGA(RGF)-CXCR4L nanoparticles decreased cell viability and proliferation by inhibiting Erk and Akt phosphorylation and promoting apoptosis. Moreover, in vivo administration of 177Lu-PLGA(RGF)-CXCR4L significantly reduced tumor growth in an HCT116 colorectal cancer xenograft model. The biokinetic profile showed hepatic and renal elimination.

Discussion

Data obtained in this research justify additional preclinical safety trials and the clinical evaluation of 177Lu-PLGA(RGF)-CXCR4L as a potential combined treatment of colorectal cancer.

Regorafenib inhibits EphA2 phosphorylation and leads to liver damage via the ERK/MDM2/p53 axis

The hepatotoxicity of regorafenib is one of the most noteworthy concerns for patients, however the mechanism is poorly understood. Hence, there is a lack of effective intervention strategies. Here, by comparing the target with sorafenib, we show that regorafenib-induced liver injury is mainly due to its nontherapeutic target Eph receptor A2 (EphA2). EphA2 deficiency attenuated liver damage and cell apoptosis under regorafenib treatment in male mice. Mechanistically, regorafenib inhibits EphA2 Ser897 phosphorylation and reduces ubiquitination of p53 by altering the intracellular localization of mouse double minute 2 (MDM2) by affecting the extracellular signal-regulated kinase (ERK)/MDM2 axis. Meanwhile, we found that schisandrin C, which can upregulate the phosphorylation of EphA2 at Ser897 also has protective effect against the toxicity in vivo. Collectively, our findings identify the inhibition of EphA2 Ser897 phosphorylation as a key cause of regorafenib-induced hepatotoxicity, and chemical activation of EphA2 Ser897 represents a potential therapeutic strategy to prevent regorafenib-induced hepatotoxicity.

Regorafenib monotherapy as second-line treatment of patients with RAS-mutant advanced colorectal cancer (STREAM): an academic, multicenter, single-arm, two-stage, phase II study

BACKGROUND

Maintaining angiogenesis inhibition and switching the chemotherapy backbone represent the current second-line therapy in patients with RAS-mutant metastatic colorectal cancer (mCRC). Regorafenib, an oral multikinase inhibitor, prolonged overall survival (OS) in the chemorefractory setting.

MATERIALS AND METHODS

STREAM was an academic, multicenter, single-arm phase II trial, evaluating the activity of regorafenib in RAS-mutant mCRC, in terms of the rate of patients who were progression-free after 6 months from study entry (6mo-PF). Patients were pretreated with fluoropyrimidine, oxaliplatin, and bevacizumab. According to Simon's two-stage design, ≥18 patients 6mo-PF were needed in the overall population (N = 46). Secondary endpoints were safety, objective response rate (ORR), progression-free survival (PFS), and OS. Early metabolic response by [¹⁸F]2-fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography ([¹⁸F]-FDG PET/CT) scan was an exploratory endpoint. EudraCT Number: 2015-001105-13.

RESULTS

The number of patients 6mo-PF was 8/22 at the first stage and 14/46 in the overall population. The ORR was 10.9%, disease control rate was 54.6%, median (m)PFS was 3.6 months [95% confidence interval (CI) 1.9-6.7 months], mOS was 18.9 months (95% CI 10.3-35.3 months), and mPFS2 (from study entry to subsequent-line progression) was 13.3 months (95% CI 8.4-19.7 months). Long benefiter patients (>6mo-PF) significantly more often had a single metastatic site and lung-limited disease. No unexpected toxicity was reported. Grade ≥3 events occurred in 39.1% of patients, with hand-foot syndrome (13%), fatigue, and hyperbilirubinemia (6.5%) occurring mostly. Baseline metabolic assessment was associated with OS in the multivariate analysis, while early metabolic response was not associated with clinical outcomes.

CONCLUSIONS

The study did not meet its primary endpoint. However, regorafenib was well tolerated and did not preclude subsequent treatments. Patients with good prognostic features (single metastatic site and lung-limited disease) reported clinical benefit with regorafenib. The exploratory metabolic analysis suggests that baseline [¹⁸F]-FDG PET/CT might be useful to select patients with a favorable outcome. A chemotherapy-free interval with regorafenib was associated with durable disease control in a selected group of patients with favorable clinical characteristics.

Regorafenib induces Bim-mediated intrinsic apoptosis by blocking AKT-mediated FOXO3a nuclear export

Regorafenib (REGO) is a synthetic oral multi-kinase inhibitor with potent antitumor activity. In this study, we investigate the molecular mechanisms by which REGO induces apoptosis. REGO induced cytotoxicity, inhibited the proliferation and migration ability of cells, and induced nuclear condensation, and reactive oxygen species (ROS)-dependent apoptosis in cancer cells. REGO downregulated PI3K and p-AKT level, and prevented FOXO3a nuclear export. Most importantly, AKT agonist (SC79) not only inhibited REGO-induced FOXO3a nuclear localization and apoptosis but also restored the proliferation and migration ability of cancer cells, further demonstrating that REGO prevented FOXO3a nuclear export by deactivating PI3K/AKT. REGO treatment promotes Bim expression via the FOXO3a nuclear localization pathway following PI3K/AKT inactivation. REGO induced Bim upregulation and translocation into mitochondria as well as Bim-mediated Bax translocation into mitochondria. Fluorescence resonance energy transfer (FRET) analysis showed that REGO enhanced the binding of Bim to Bak/Bax. Knockdown of Bim, Bak and Bax respectively almost completely inhibited REGO-induced apoptosis, demonstrating the key role of Bim by directly activating Bax/Bak. Knockdown of Bax but not Bak inhibited REGO-induced Drp1 oligomerization in mitochondria. In conclusion, our data demonstrate that REGO promotes apoptosis via the PI3K/AKT/FOXO3a/Bim-mediated intrinsic pathway.

The sodium channel subunit SCNN1B suppresses colorectal cancer via suppression of active c-Raf and MAPK signaling cascade

The incidence of colorectal cancer (CRC) is rising worldwide. Here, we identified SCNN1B as an outlier down-regulated in CRC and it functions as a tumor suppressor. SCNN1B mRNA and protein expression were down-regulated in primary CRC and CRC cells. In a tissue microarray cohort (N = 153), SCNN1B protein was an independent prognostic factor for favorable outcomes in CRC. Ectopic expression of SCNN1B in CRC cell lines suppressed cell proliferation, induced apoptosis, and cell cycle arrest, and suppressed cell migration in vitro. Xenograft models validated tumor suppressive function of SCNN1B in vivo. Mechanistically, Gene Set Enrichment Analysis (GSEA) showed that SCNN1B correlates with KRAS signaling. Consistently, MAPK qPCR and kinase arrays revealed that SCNN1B suppressed MAPK signaling. In particular, SCNN1B overexpression suppressed p-MEK/p-ERK expression and SRE-mediated transcription activities, confirming blockade of Ras-Raf-MEK-ERK cascade. Mechanistically, SCNN1B did not affect KRAS activation, instead impairing activation of c-Raf by inducing its inhibitory phosphorylation and targeting active c-Raf for degradation. The ectopic expression of c-Raf fully rescued cell proliferation and colony formation in SCNN1B-overexpressing CRC cells, confirming c-Raf as the principal molecular target of SCNN1B. In summary, we identified SCNN1B as a tumor suppressor by functioning as a c-Raf antagonist, which in turn suppressed oncogenic MEK-ERK signaling.

Recent Advancements, Limitations, and Future Perspectives of the use of Personalized Medicine in Treatment of Colon Cancer

Due to the heterogeneity of colon cancer, surgery, chemotherapy, and radiation are ineffective in all cases. The genomic profile and biomarkers associated with the process are considered in personalized medicine, along with the patient's personal history. It is based on the response of the targeted therapies to specific genetic variations. The patient's genetic transcriptomic and epigenetic features are evaluated, and the best therapeutic approach and diagnostic testing are identified through personalized medicine. This review aims to summarize all the necessary, updated information on colon cancer related to personalized medicine. Personalized medicine is gaining prominence as generalized treatments are finding it challenging to contain colon cancer cases which currently rank fourth among global cancer incidence while being the fifth largest in total death cases worldwide. In personalized therapy, patients are grouped into specific categories, and the best therapeutic approach is chosen based on evaluating their molecular features. Various personalized strategies are currently being explored in the treatment of colon cancer involving immunotherapy, phytochemicals, and other biomarker-specific targeted therapies. However, significant challenges must be overcome to integrate personalized medicine into healthcare systems completely. We look at the various signaling pathways and genetic and epigenetic alterations associated with colon cancer to understand and identify biomarkers useful in targeted therapy. The current personalized therapies available in colon cancer treatment and the strategies being explored to improve the existing methods are discussed. This review highlights the advantages and limitations of personalized medicine in colon cancer therapy. The current scenario of personalized medicine in developed countries and the challenges faced in middle- and low-income countries are also summarized. Finally, we discuss the future perspectives of personalized medicine in colon cancer and how it could be integrated into the healthcare systems.

Synergistic antitumor activity of regorafenib and rosuvastatin in colorectal cancer

Introduction: Colorectal cancer is one of the most prevalent life-threatening malignant tumors with high incidence and mortality. However, the efficacy of current therapeutic regimens is very limited. Regorafenib has been approved for second- or third-line treatment of patients who are refractory to standard chemotherapy diagnosed with metastatic colorectal cancer, but its clinical efficacy needs to be further improved. Accumulating evidence demonstrates that statins also possess potent anticancer activities. However, whether regorafenib and statins pose synergistic anticancer effects in colorectal cancer is still unclear. Methods: Sulforhodamine B (SRB) assays were applied to evaluate the anti-proliferative activity of regorafenib or/and rosuvastatin in vitro, and immunoblotting analysis were applied to detect the effects of regorafenib/rosuvastatin combined treatment on mitogen-activated protein kinase (MAPK) signaling and apoptosis-related proteins. MC38 tumors were applied to investigate the synergistic anticancer effects of regorafenib in combination with rosuvastatin in vivo. Results: We found that regorafenib in combination with rosuvastatin exerted significant synergistic inhibition against colorectal cancer growth in vitro and in vivo. Mechanistically, regorafenib and rosuvastatin combination synergistically suppressed MAPK signaling, a crucial signaling pathway promoting cell survival, as indicated by the reduction of phosphorylated MEK/ERK. In addition, regorafenib in combination with rosuvastatin synergistically induced the apoptosis of colorectal cancer in vitro and in vivo. Discussion: Our study demonstrated the synergistic anti-proliferative and pro-apoptotic effects of regorafenib/rosuvastatin combined treatment in colorectal cancer in vitro/vivo and might potentially be evaluated as a novel combination regimen for clinical treatment of colorectal cancer.

Dual inhibition of BET and HAT/p300 suppresses colorectal cancer via DR5- and p53/PUMA-mediated cell death

Background

Colorectal cancer (CRC) frequently has a dysregulated epigenome causing aberrant up-regulation of oncogenes such as c-MYC. Bromodomain and extra-terminal domain (BET) proteins and histone acetyltransferases (HAT) are epigenetic regulatory proteins that create and maintain epigenetic states supporting oncogenesis. BET inhibitors and HAT inhibitors are currently being investigated as cancer therapeutics due to their ability to suppress cancer-promoting epigenetic modifiers. Due to the extensive molecular crosstalk between BET proteins and HAT proteins, we hypothesized that dual inhibition of BET and HAT could more potently inhibit CRC cells than inhibition of each individual protein.

Methods

We investigated the activity and mechanisms of a dual BET and HAT inhibitor, NEO2734, in CRC cell lines and mouse xenografts. MTS, flow cytometry, and microscopy were used to assess cell viability. qPCR, Western blotting, and immunofluorescent staining were used to assess mechanisms of action.

Results

We found that NEO2734 more potently suppresses CRC cell growth than first generation BET inhibitors, regardless of the status of common CRC driver mutations. We previously showed that BET inhibitors upregulate DR5 to induce extrinsic apoptosis. In the current study, we show that NEO2734 treatment induces CRC cell apoptosis via both the intrinsic and extrinsic apoptosis pathways. NEO2734 increases p53 expression and subsequently increased expression of the p53-upregulated mediator of apoptosis (PUMA), which is a critical mechanism for activating intrinsic apoptosis. We demonstrate that inhibition of either the intrinsic or extrinsic branches of apoptosis partially rescues CRC cells from NEO2734 treatment, while the dual inhibition of both branches of apoptosis more strongly rescues CRC cells from NEO2734 treatment. Finally, we show that NEO2734 monotherapy is able to suppress tumor growth in CRC xenografts by inducing apoptosis.

Conclusions

Our study demonstrates NEO2734 potently suppresses CRC cells in vitro and in vivo by simultaneously upregulating PUMA and DR5 to induce cell death. Further studies of NEO2734 for treating CRC are warranted.

Regorafenib induces the apoptosis of gastrointestinal cancer-associated fibroblasts by inhibiting AKT phosphorylation

Cancer-associated fibroblasts (CAFs) are a key component of tumor microenvironment and are essential for tumorigenesis and development. Regorafenib is a multikinase inhibitor that targets CAFs and suppresses tumor growth. Here, we investigated the effects of regorafenib on gastrointestinal CAFs and the underlying molecular mechanisms. First, we established two in vivo tumor models, the cancer cell line HCT116 with or without mesenchymal stem cells (MSCs) and treated them with regorafenib. We found that the application of regorafenib potently impaired tumor growth, an effect that was more pronounced in tumors with a high stromal ratio, thus demonstrating that regorafenib can inhibit CAFs proliferation and induce CAFs apoptosis in vivo. Moreover, we showed that regorafenib affected macrophage infiltration by reducing the proportion of CAFs in tumors. Afterward, we induced MSCs into CAFs with exosomes to establish an in vitro model. Then, we used MTS and flow cytometry to detect the effects of regorafenib on the proliferation and apoptosis of CAFs, and Western blot to determine the expression level of apoptosis-related proteins. We found that regorafenib inhibited the proliferation of CAFs and induced the apoptosis of CAFs in vitro. Furthermore, Western blot results showed that regorafenib down-regulated the expression of B-cell lymphoma-2 (Bcl-2) and concurrently up-regulated the expression of Bcl-2-associated X (Bax), and regorafenib inhibited the phosphorylation pathway of AKT in CAFs. In conclusion, our results provide a model in which regorafenib induces CAFs apoptosis by inhibiting the phosphorylation of AKT, and regorafenib affects macrophage infiltration by reducing the proportion of CAFs in tumor tissues.

Inhibition of the PINK1-Parkin Pathway Enhances the Lethality of Sorafenib and Regorafenib in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common fatal malignancies and the main cause of cancer-related deaths. The multitarget tyrosine kinase inhibitors (TKIs) sorafenib and regorafenib are systemic therapeutic drugs approved for the treatment of HCC. Here, we found that sorafenib and regorafenib injured mitochondria by inducing mitochondrial Ca²⁺ (mtCa²⁺) overload and mitochondrial permeability transition pore (mPTP) opening, resulting in mitochondria-mediated cell death, which was alleviated by cyclosporin A (CsA), an inhibitor of mPTP. Meanwhile, mPTP opening caused PINK1 accumulation on damaged mitochondria, which recruited Parkin to mitochondria to induce mitophagy. Inhibition of autophagy by the lysosomal inhibitor chloroquine (CQ) or inhibition of mitochondrial fission by mdivi-1 aggravated sorafenib- and regorafenib-induced cell death. Moreover, knockdown of PINK1 also promotes sorafenib- and regorafenib-induced cell death. An in vivo study showed that sorafenib and regorafenib inhibited HepG2 cell growth more effectively in PINK1 knockdown cells than in shNTC cells in null mice. Thus, our data demonstrate that PINK1-Parkin-mediated mitophagy alleviates sorafenib and regorafenib antitumor effects in vitro and in vivo.

BET protein degradation triggers DR5-mediated immunogenic cell death to suppress colorectal cancer and potentiate immune checkpoint blockade

Bromodomain and extra-terminal domain (BET) family proteins are epigenetic readers that play a critical role in oncogenesis by controlling the expression of oncogenes such as c-Myc. Targeting BET family proteins has recently emerged as a promising anticancer strategy. However, the molecular mechanisms by which cancer cells respond to BET inhibition are not well understood. In this study, we found that inducing the degradation of BET proteins by the proteolysis targeting chimeras (PROTAC) approach potently suppressed the growth of colorectal cancer (CRC) including patient-derived tumors. Mechanistically, BET degradation transcriptionally activates Death Receptor 5 (DR5) to trigger immunogenic cell death (ICD) in CRC cells. Enhanced DR5 induction further sensitizes CRC cells with a mutation in Speckle-type POZ protein (SPOP). Furthermore, DR5 is indispensable for a striking antitumor effect of combining BET degradation and anti-PD-1 antibody, which was well tolerated in mice and almost eradicated syngeneic tumors. Our results demonstrate that BET degradation triggers DR5-mediated ICD to potently suppress CRC and potentiate immune checkpoint blockade. These results provide a rationale, mechanistic insights, and potential biomarkers for developing a precision CRC therapy by inducing BET protein degradation.

Molecular Subtyping Combined with Biological Pathway Analyses to Study Regorafenib Response in Clinically Relevant Mouse Models of Colorectal Cancer

PURPOSE

Regorafenib (REG) is approved for the treatment of metastatic colorectal cancer, but has modest survival benefit and associated toxicities. Robust predictive/early response biomarkers to aid patient stratification are outstanding. We have exploited biological pathway analyses in a patient-derived xenograft (PDX) trial to study REG response mechanisms and elucidate putative biomarkers.

EXPERIMENTAL DESIGN

Molecularly subtyped PDXs were annotated for REG response. Subtyping was based on gene expression (CMS, consensus molecular subtype) and copy-number alteration (CNA). Baseline tumor vascularization, apoptosis, and proliferation signatures were studied to identify predictive biomarkers within subtypes. Phospho-proteomic analysis was used to identify novel classifiers. Supervised RNA sequencing analysis was performed on PDXs that progressed, or did not progress, following REG treatment.

RESULTS

Improved REG response was observed in CMS4, although intra-subtype response was variable. Tumor vascularity did not correlate with outcome. In CMS4 tumors, reduced proliferation and higher sensitivity to apoptosis at baseline correlated with response. Reverse phase protein array (RPPA) analysis revealed 4 phospho-proteomic clusters, one of which was enriched with non-progressor models. A classification decision tree trained on RPPA- and CMS-based assignments discriminated non-progressors from progressors with 92% overall accuracy (97% sensitivity, 67% specificity). Supervised RNA sequencing revealed that higher basal EPHA2 expression is associated with REG resistance.

CONCLUSIONS

Subtype classification systems represent canonical "termini a quo" (starting points) to support REG biomarker identification, and provide a platform to identify resistance mechanisms and novel contexts of vulnerability. Incorporating functional characterization of biological systems may optimize the biomarker identification process for multitargeted kinase inhibitors.

BRD9 inhibition promotes PUMA-dependent apoptosis and augments the effect of imatinib in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are primarily characterized by activating mutations of tyrosine kinase or platelet-derived growth factor receptor alpha. Although the revolutionary therapeutic outcomes of imatinib are well known, the long-term benefits of imatinib are still unclear. The effects of BRD9, a recently identified subunit of noncanonical BAF complex (ncBAF) chromatin remodeling complexes, in GISTs are not clear. In the current study, we evaluated the functional role of BRD9 in GIST progression. Our findings demonstrated that the expression of BRD9 was upregulated in GIST tissues. The downregulation or inhibition of BRD9 could significantly reduce cellular proliferation, and facilitates apoptosis in GISTs. BRD9 inhibition could promote PUMA-dependent apoptosis in GISTs and enhance imatinib activity in vitro and in vivo. BRD9 inhibition synergizes with imatinib in GISTs by inducing PUMA upregulation. Mechanism study revealed that BRD9 inhibition promotes PUMA induction via the TUFT1/AKT/GSK-3β/p65 axis. Furthermore, imatinib also upregulates PUMA by targeting AKT/GSK-3β/p65 axis. In conclusion, our results indicated that BRD9 plays a key role in the progression of GISTs. Inhibition of BRD9 is a novel therapeutic strategy in GISTs treated alone or in combination with imatinib.

Characterization and clinical evaluation of microsatellite instability and loss of heterozygosity within tumor-related genes in colorectal cancer

BACKGROUND

Microsatellite instability (MSI) is a biomarker for better outcomes in colorectal cancer (CRC). However, this conclusion is controversial. In addition, MSs can be a useful marker for loss of heterozygosity (LOH) of genes, but this finding has not been well studied. Here, we aimed to clarify the predictive value of MSI/LOH within tumor-related genes in CRC.

METHODS

We detected MSI/LOH of MSs in tumor-related genes and the Bethesda (B5) panel by STR scanning and cloning/sequencing. We further analyzed the relationship between MSI/LOH status and clinical features or outcomes by Pearson's Chi-square test, Fisher's exact test and the Kaplan-Meier method.

RESULTS

The findings indicated that the MSI rates of B5 loci were all higher than those of loci in tumor-related genes. Interestingly, MSI/LOH of 2 loci in the B5 panel and 12 loci in tumor-related genes were associated with poorer outcomes, while MSI/LOH of the B5 panel failed to predict outcomes in CRC. MSI of BAT25, MSI/LOH of BAT26 and MSI of the B5 panel showed closer relationships with mucinous carcinoma. In addition, LOH-H of the B5 panel was associated with increased lymphatic metastasis.

CONCLUSIONS

In summary, MSI/LOH of certain loci or the whole panel of B5 is related to clinical features, and several loci within tumor-related genes showed prognostic value in the outcomes of CRC.

Caspase-3: A primary target for natural and synthetic compounds for cancer therapy

Caspases, a group of protease enzymes (cysteine proteases), exist as inactive zymogens in the cells and execute apoptosis (programmed cell death). Caspase-3, an executioner caspase, plays an imperative role in apoptosis and becomes a primary target for cancer treatment. A number of analogues of quinazoline, quinazolinone, indoloquinazolines, quinone, naphthoquinones, pyrroloiminoquinones, styrylquinolines, tetheredtetrahydroquinoline, fluoroquinolone, thiosemicarbazones, benzotriazole, pyrimidines, chalcone, and carbazoles have been reported till date, representing caspase-3 mediated apoptosis for cancer therapy. Simultaneously, plant isolates, including lysicamine, podophyllotoxin, and majoranolide, have also been claimed for caspase-3-mediated apoptosis-induced cytotoxicity. Procaspase-activating compound-1 (PAC-1) is the first FDA approved orphan drug, and its synthetic derivative WF-208 also showed fascinating caspase-3 mediated anticancer activity. Till date, a large number of compounds have been reported and patented for their caspase-3-mediated cytotoxicity and now scientist is also focusing to introduce new compounds in market to encompass anticancer activity.

The Role of p53 Dysfunction in Colorectal Cancer and Its Implication for Therapy

Colorectal cancer (CRC) is one of the most common and fatal cancers worldwide. The carcinogenesis of CRC is based on a stepwise accumulation of mutations, leading either to an activation of oncogenes or a deactivation of suppressor genes. The loss of genetic stability triggers activation of proto-oncogenes (e.g., KRAS) and inactivation of tumor suppression genes, namely TP53 and APC, which together drive the transition from adenoma to adenocarcinoma. On the one hand, p53 mutations confer resistance to classical chemotherapy but, on the other hand, they open the door for immunotherapy, as p53-mutated tumors are rich in neoantigens. Aberrant function of the TP53 gene product, p53, also affects stromal and non-stromal cells in the tumor microenvironment. Cancer-associated fibroblasts together with other immunosuppressive cells become valuable assets for the tumor by p53-mediated tumor signaling. In this review, we address the manifold implications of p53 mutations in CRC regarding therapy, treatment response and personalized medicine.

Sequenced treatment after regorafenib and survival in metastatic colorectal cancer: a qualitative clinical review

There is limited evidence-based guidance regarding treatment sequencing and outcomes following regorafenib in patients with refractory metastatic colorectal cancer (mCRC). A targeted literature review was conducted to identify studies with clinical outcomes associated with regorafenib therapy and subsequent treatment following regorafenib therapy. The median overall survival range of the nine studies with sequenced-based survival data was 2.1–19.3 months for regorafenib prior to subsequent therapy in refractory mCRC. Safety outcomes in patients treated with regorafenib prior to other therapies in mCRC were generally comparable to reported adverse events in clinical trials for subsequent agents. Data from this review demonstrate a potential correlation between survival and the use of regorafenib prior to subsequent chemotherapy or targeted therapy in patients with refractory mCRC.

P53-independent partial restoration of the p53 pathway in tumors with mutated p53 through ATF4 transcriptional modulation by ERK1/2 and CDK9

A long-term goal in the cancer-field has been to develop strategies for treating p53-mutated tumors. A novel small-molecule, PG3-Oc, restores p53 pathway-signaling in tumor cells with mutant-p53, independently of p53/p73. PG3-Oc partially upregulates the p53-transcriptome (13.7% of public p53 target-gene dataset; 15.2% of in-house dataset) and p53-proteome (18%, HT29; 16%, HCT116-p53^−/−). Bioinformatic analysis indicates critical p53-effectors of growth-arrest (p21), apoptosis (PUMA, DR5, Noxa), autophagy (DRAM1), and metastasis-suppression (NDRG1) are induced by PG3-Oc. ERK1/2- and CDK9-kinases are required to upregulate ATF4 by PG3-Oc which restores p53 transcriptomic-targets in cells without functional-p53. PG3-Oc represses MYC (ATF4-independent), and upregulates PUMA (ATF4-dependent) in mediating cell death. With largely nonoverlapping transcriptomes, induced-ATF4 restores p53 transcriptomic targets in drug-treated cells including functionally important mediators such as PUMA and DR5. Our results demonstrate novel p53-independent drug-induced molecular reprogramming involving ERK1/2, CDK9, and ATF4 to restore upregulation of p53 effector genes required for cell death and tumor suppression.

Regorafenib inhibits migration, invasion, and vasculogenic mimicry of hepatocellular carcinoma via targeting ID1-mediated EMT

Regorafenib is approved for patients with unresectable hepatocellular carcinoma (HCC) following sorafenib. However, the effect of regorafenib on HCC metastasis and its mechanism are poorly understood. Here, our data showed that regorafenib significantly restrained the migration, invasion and vasculogenic mimicry (VM) of HCC cells, and downregulated the expression of epithelial-to-mesenchymal transition (EMT)/VM-related molecules. Using RNA-seq and cellular thermal shift assays, we found that inhibitor of differentiation 1 (ID1) was a key target of regorafenib. In HCC tissues, the protein expression of ID1 was positively correlated with EMT and VM formation (CD34- /PAS+ ). Functionally, ID1 knockdown inhibited HCC cell migration, invasion, metastasis, and VM formation in vitro and in vivo, with upregulation of E-cadherin and downregulation of Snail and VE-cadherin. Moreover, Snail overexpression promoted the migration, invasion, and VM formation of ID1 knockdown cells. Snail knockdown reduced the migration, invasion, and VM formation of ID1 overexpression cells. Finally, regorafenib suppressed VM formation and decreased the expression of ID1, VE-cadherin and Snail in HCC PDX model. In conclusion, we manifested that regorafenib distinctly inhibited EMT in HCC cells via targeting ID1, leading to the suppression of cell migration, invasion and VM formation. These findings suggest that regorafenib may be developed as a suitable therapeutic agent for HCC metastasis.

A small natural molecule CADPE kills residual colorectal cancer cells by inhibiting key transcription factors and translation initiation factors

Residual disease is the major cause for colorectal cancer (CRC) relapse. Herein, we explore whether and how a natural molecule CADPE killed heterogenic populations in a panel of CRC cell lines with KRAS/BRAF mutations that are natively resistant to EGFR- or VEGFR-targeted therapy, without sparing persistent cells, a reservoir of the disease relapse. Results showed that CADPE killed the tumor bulk and residual cells in the panel of CRC cell lines, rapidly inactivated c-Myc, STAT3, and NF-κB, and then decreased the protein levels of key signaling molecules for CRC, such as β-catenin, Notch1, and the nodes of mTOR pathways; eukaryotic translation initiation factors (eIF4F); anti-apoptotic proteins (Bcl-xl, Mcl-1, and survivin); and stemness-supporting molecules (CD133, Bim-1, and VEGF). In terms of mechanism of action, concurrent downregulation of Mcl-1, Bcl-xl, and survivin was necessary for CADPE to kill CRC bulk cells, while additional depletion of CD133 and VEGF proteins was required for killing the residual CRC cells. Moreover, the disabled c-Myc, STAT3, NF-κB, and eIF4F were associated with the broadly decreased levels of anti-apoptosis proteins and pro-stemness proteins. Consistently, CADPE suppressed CRC tumor growth associated with robust apoptosis and depleted levels of c-Myc, STAT3, NF-κB, eIF4F, anti-apoptotic proteins, and pro-stemness proteins. Our findings showed the promise of CADPE for treating CRC and suggested a rational polytherapy that disables c-Myc, STAT3, NF-κB, and eIF4F for killing CRC residual disease.

Copanlisib promotes growth inhibition and apoptosis by modulating the AKT/FoxO3a/PUMA axis in colorectal cancer

Colorectal cancer (CRC) is the type of cancer with the third highest incidence and is associated with high mortality and low 5-year survival rates. We observed that copanlisib, an inhibitor of PI3K (pan-class I phosphoinositide 3-kinase) that preferentially inhibits PI3Kδ and PI3Kα, impedes the growth of CRC cells by inducing apoptosis via PUMA. There was a marked increase in the expression of PUMA independent of p53 after treatment with copanlisib. The response of CRC cells to copanlisib could be predicted by PUMA expression. Copanlisib was found to induce PUMA expression through FoxO3a by directly binding to the PUMA promoter after inhibiting AKT signaling. PUMA deficiency mitigated the apoptosis induced by copanlisib. Caspase activation and mitochondrial dysfunction led to copanlisib resistance, as observed through a clonogenic assay, whereas enhanced expression of PUMA increased the copanlisib-induced susceptibility to apoptosis. Moreover, the antitumor effects of copanlisib were suppressed by a deficiency of PUMA in a xenograft model, and caspase activation and reduced apoptosis were also observed in vivo. Copanlisib-mediated chemosensitization seemed to involve the concurrent induction of PUMA expression via mechanisms that were both dependent and independent of p53. These observations indicate that apoptosis mediated by PUMA is crucial for the anticancer effects of copanlisib and that manipulation of PUMA may aid in enhancing anticancer activities.

Synthesis, in vitro, and in vivo evaluation of novel N-phenylindazolyl diarylureas as potential anti-cancer agents

Novel N-phenylindazole based diarylureas have been designed, synthesized and evaluated as potential anticancer agents. In vitro cell viability studies of these derivatives illustrate good potency with IC₅₀ values in the range of 0.4–50 μM in several cancer cell lines including murine metastatic breast cancer 4T1, murine glioblastoma GL261, human triple negative breast cancer MDA-MB-231, human pancreatic cancer MIAPaCa-2, and human colorectal cancer cell line WiDr. The ester group in the lead compound 8i was modified to incorporate amino-amides to increase solubility and stability while retaining biological activity. Further in vitro studies reveal that lead candidates inhibit tube length in HUVEC cells. In vivo systemic toxicity studies indicate that these candidate compounds are well tolerated in mice without any significant side effects. Anticancer efficacy studies in WiDr tumor xenograft and 4T1 tumor syngraft models demonstrate that the lead candidate 11 exhibits significant antitumor properties as a single agent in these tumor models.

Sirt3 promotes hepatocellular carcinoma cells sensitivity to regorafenib through the acceleration of mitochondrial dysfunction

Regorafenib, a multiple kinase inhibitor, is recently approved for treatment of patients with advanced hepatocellular carcinoma (HCC). Previous studies demonstrated that regorafenib was a mitochondrial toxicant, which associated with the impairment of mitochondria. Sirt3 is involved in the regulation of mitochondrial function in cancers. This study aimed to investigate the mechanism of Sirt3 involved in the mitochondrial dysfunction which associated with regorafenib treatment in liver cancer cells. We found regorafenib inhibited Sirt3 and p-ERK expression in HCC cells in a dose-dependent manner. Bioinformatics analysis showed that Sirt3 expression was down-regulated in liver cancer tissues and its low expression was correlated with worse overall survival (OS) in liver cancer patients. After transfected with Sirt3 overexpression plasmid, we found that Sirt3 sensitized liver cancer cells to regorafenib and resulted in much more apoptosis with a significant increase of ROS level. However, exogenous antioxidant could not weaken the apoptosis. Mitochondrial membrane potential assay indicated that Sirt3 overexpression accelerated the mitochondrial depolarization process induced by regorafenib and aggravated mitochondrial injury. Cellular oxygen consumption assay showed that mitochondrial dysfunction was caused by the damage of the electron transport chain. The results demonstrated that Sirt3 overexpression promoted the increase of ROS and apoptosis induced by regorafenib through the acceleration of mitochondrial dysfunction by impairing function of the electron transport chain in liver cancer cells. Our studies verified the functional role of Sirt3 in regorafenib treatment and suggested that regorafenib accompanied with Sirt3 activator as a novel treatment strategy for HCC.

Mcl-1 inhibition overcomes intrinsic and acquired regorafenib resistance in colorectal cancer

Intrinsic and acquired resistance to targeted therapies is a significant clinical problem in cancer. We previously showed that resistance to regorafenib, a multi-kinase inhibitor for treating colorectal cancer (CRC) patients, can be caused by mutations in the tumor suppressor FBW7, which block degradation of the pro-survival Bcl-2 family protein Mcl-1. We tested if Mcl-1 inhibition can be used to develop a precision combination therapy for overcoming regorafenib resistance.

METHODS

Small-molecule Mcl-1 inhibitors were tested on CRC cells with knock-in (KI) of a non-degradable Mcl-1. Effects of Mcl-1 inhibitors on regorafenib sensitivity were determined in FBW7-mutant and -wild-type (WT) CRC cells and tumors, and in those with acquired regorafenib resistance due to enriched FBW7 mutations. Furthermore, translational potential was explored by establishing and analyzing FBW7-mutant and -WT patient-derived organoid (PDO) and xenograft (PDX) tumor models.

RESULTS

We found that highly potent and specific Mcl-1 inhibitors such as S63845 overcame regorafenib resistance by restoring apoptosis in multiple regorafenib-resistant CRC models. Mcl-1 inhibition re-sensitized CRC tumors with intrinsic and acquired regorafenib resistance in vitro and in vivo, including those with FBW7 mutations. Importantly, Mcl-1 inhibition also sensitized FBW7-mutant PDO and PDX models to regorafenib. In contrast, Mcl-1 inhibition had no effect in FBW7-WT CRCs.

CONCLUSIONS

Our results demonstrate that Mcl-1 inhibitors can overcome intrinsic and acquired regorafenib resistance in CRCs by restoring apoptotic response. FBW7 mutations might be a potential biomarker predicting for response to the regorafenib/Mcl-1 inhibitor combination.

Regorafenib suppresses epidermal growth factor receptor signaling-modulated progression of colorectal cancer

Active epidermal growth factor receptors (EGFR) signaling mediates the progression of colorectal cancer (CRC) through activation of downstream kinases and transcription factors. The increased expression of EGFR was associated with worse prognosis in patients with metastatic CRC (mCRC). Regorafenib, the oral kinase inhibitor approved for the treatment of mCRC, has been shown to reduce activation of downstream kinases of EGFR signal pathway in hepatocellular carcinoma and osteosarcoma. However, whether EGFR inactivation was participates in regorafenib-inhibited progression of CRC still remaining ambiguous. The major purpose of present study was to verify effect of regorafenib on EGFR signaling-mediated progression of CRC. Here, we investigated the effect of regorafenib or erlotinib (EGFR inhibitor) on tumor cell growth, invasion ability, apoptotic, and EGFR signal transduction in CRC in vitro and in vivo. Our results indicated regorafenib reduced EGF-induced EGFR and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activity. Both regorafenib and erlotinib significantly reduced cell invasion ability, activation of protein kinase C-δ (PKCδ), protein kinase B (AKT), extracellular signal-regulated kinases (ERK), and NF-κB. Regorafenib can trigger the inhibition of tumor cell growth and the induction of apoptosis through extrinsic/intrinsic apoptosis pathways. In addition, the expression of NF-κB-mediated proteins involved in tumor progression was also suppressed by regorafenib treatment. Taken together, regorafenib acts as a inhibitor of EGFR signaling that attenuated the activation of EGFR and EGFR related downstream signaling cascades in CRC. Our results suggested that the suppression of EGFR signaling was associated with regorafenib-inhibited progression of CRC.

Immunogenic cell death in colon cancer prevention and therapy

Colorectal cancer (CRC) is a leading cause of cancer-related death worldwide. The colonic mucosa constitutes a critical barrier and a major site of immune regulation. The immune system plays important roles in cancer development and treatment, and immune activation caused by chronic infection or inflammation is well-known to increase cancer risk. During tumor development, neoplastic cells continuously interact with and shape the tumor microenvironment (TME), which becomes progressively immunosuppressive. The clinical success of immune checkpoint blockade therapies is limited to a small set of CRCs with high tumor mutational load and tumor-infiltrating T cells. Induction of immunogenic cell death (ICD), a type of cell death eliciting an immune response, can therefore help break the immunosuppressive TME, engage the innate components, and prime T cell-mediated adaptive immunity for long-term tumor control. In this review, we discuss the current understanding of ICD induced by antineoplastic agents, the influence of driver mutations, and recent developments to harness ICD in colon cancer. Mechanism-guided combinations of ICD-inducing agents with immunotherapy and actionable biomarkers will likely offer more tailored and durable benefits to patients with colon cancer.

The Role of p53-Mediated Signaling in the Therapeutic Response of Colorectal Cancer to 9F, a Spermine-Modified Naphthalene Diimide Derivative

Colorectal cancer (CRC) is one of the most prevalent cancers due to its frequency and high rate of mortality. Polyamine-vectorized anticancer drugs possess multiple biological properties. Of these drugs, 9F has been shown to inhibit tumor growth and the metastasis of hepatocellular carcinoma. This current study aims to investigate the effects of 9F on CRC and determine its molecular mechanisms of action. Our findings demonstrate that 9F inhibits CRC cell growth by inducing apoptosis and cell cycle arrest, and suppresses migration, invasion and angiogenesis in vitro, resulting in the inhibition of tumor growth and metastasis in vivo. Based on RNA-seq data, further bioinformatic analyses suggest that 9F exerts its anticancer activities through p53 signaling, which is responsible for the altered expression of key regulators of the cell cycle, apoptosis, the epithelial-to-mesenchymal transition (EMT), and angiogenesis. In addition, 9F is more effective than amonafide against CRC. These results show that 9F can be considered as a potential strategy for CRC treatment.

Gilteritinib induces PUMA-dependent apoptotic cell death via AKT/GSK-3β/NF-κB pathway in colorectal cancer cells

As a highly potent and highly selective oral inhibitor of FLT3/AXL, gilteritinib showed activity against FLT3D835 and FLT3‐ITD mutations in pre‐clinical testing, although its role on colorectal cancer (CRC) cells is not yet fully elucidated. We examined the activity of gilteritinib in suppressing growth of CRC and its enhancing effect on other drugs used in chemotherapy. In this study, we observed that, regardless of p53 status, treatment using gilteritinib induces PUMA in CRC cells via the NF‐κB pathway after inhibition of AKT and activation of glycogen synthase kinase 3β (GSK‐3β). PUMA was observed to be vital for apoptosis in CRC cells through treatment of gilteritinib. Moreover, enhancing induction of PUMA through different pathways could mediate chemosensitization by using gilteritinib. Furthermore, PUMA deficiency revoked the antitumour role of gilteritinib in vivo. Thus, our results indicate that PUMA mediates the antitumour activity of gilteritinib in CRC cells. These observations are critical for the therapeutic role of gilteritinib in CRC.

Synthesis and in vitro anticancer activity of certain novel 1-(2-methyl-6-arylpyridin-3-yl)-3-phenylureas as apoptosis-inducing agents

In connection with our research program on the development of novel anticancer candidates, herein we report the design and synthesis of novel series of 1-(2-methyl-6-arylpyridin-3-yl)-3-phenylureas 5a-l. The target pyridins were evaluated for their in vitro anticancer activity against two cancer cell lines: non-small cell lung cancer A549 cell line and colon cancer HCT-116 cell line. Compound 5l emerged as the most active congener towards both A549 and HCT-116 cell lines with IC50 values equal to 3.22 ± 0.2 and 2.71 ± 0.16 µM, respectively, which are comparable to those of Doxorubicin; 2.93 ± 0.28 and 3.10 ± 0.22, respectively. Furthermore, compound 5l stood out as the most potent pyridine derivative (mean % GI = 40), at US-NCI Developmental Therapeutic Program anticancer assay, with broad-spectrum antitumor activity against the most tested cancer cell lines from all subpanels. Compound 5l was able to provoke apoptosis in HCT-116 cells as evidenced by the decreased expression of the anti-apoptotic Bcl-2 protein, and the enhanced expression of the pro-apoptotic proteins levels; Bax, cytochrome C, p53, caspase-3 and caspase-9. Moreover, 5l disrupted the HCT-116 cell cycle via alteration of the Sub-G1 phase and arresting the G2-M stage. Also, 5l showed a significant increase in the percent of annexinV-FITC positive apoptotic cells from 1.99 to 15.76%.

Anti-tumoral activity of single and combined regorafenib treatments in preclinical models of liver and gastrointestinal cancers

Regorafenib is a sorafenib-derived chemotherapy drug belonging to the multikinase inhibitor family. This agent effectively targets a wide range of tyrosine kinases involved in cancer biology, such as those implicated in oncogenesis, angiogenesis, and tumor microenvironment control. The beneficial effects of regorafenib in clinical trials of patients who suffer from advanced hepatocellular carcinoma (HCC), colorectal cancer (CRC) or gastrointestinal stromal tumors (GISTs) refractory to standard treatments led to regorafenib monotherapy approval as a second-line treatment for advanced HCC and as a third-line treatment for advanced CRC and GISTs. Multiple in vitro and in vivo studies have been performed over the last decade to reveal the molecular mechanisms of the favorable actions exerted by regorafenib in patients. Given the hypothetical loss of sensitivity to regorafenib in tumor cells, preclinical research is also searching for novel therapeutic approaches consisting of co-administration of this drug plus other agents as a strategy to improve regorafenib effectiveness. This review summarizes the anti-tumor effects of regorafenib in single or combined treatment in preclinical models of HCC, CRC and GISTs and discusses both the global and molecular effects that account for its anti-cancer properties in the clinical setting.

The cancer drug regorafenib exhibits a broad range of anti-tumor activities that could be enhanced by combination with other treatments. A team led by José L. Mauriz from the University of León, Spain, review the ways in which regorafenib, blocking several enzymes involved in cancer biology, has been shown to shrink tumors in different models of liver, colon and gastrointestinal cancer. Its mechanisms of action include blockade of new blood vessel formation, induction of cell death and modulation of the immune microenvironment. Research studies show that co-administration of regorafenib with other drugs directed at various molecular targets or immune pathways produces synergistic effects against cancer cells. The preclinical data highlights the potential of combination drug regimens to improve outcomes among patients eligible for regorafenib treatment.

Inhibition of cyclin E1 sensitizes hepatocellular carcinoma cells to regorafenib by mcl-1 suppression

Background

To clarify the effects of cylcin E1 expression on HCC tumor progression, we studied the expression of cyclin E1 and inhibitory efficacy of regorafenib and sorafenib in HCC cells, and investigated a potential therapy that combines regorafenib treatment with cyclin E1 inhibition.

Methods

Western blotting for caspase-3 and Hoechst 33225 staining was used to measure the expression level of apoptosis-related proteins under drug treatment.

Results

Our results showed that enhanced expression of cyclin E1 after transfection compromised apoptosis in HCC cells induced by regorafenib or sorafenib. Conversely, down-regulation of cyclin E1 gene expression or inhibition of cyclin E1 by the cyclin-dependent kinase (CDK) inhibitors dinaciclib (DIN) or flavopiridol sensitized HCC cells to regorafenib and sorafenib by inducing apoptosis. The expression of Mcl-1, which is modulated by STAT3, plays a key role in regulating the therapeutic effects of CDK inhibitors. Xenograft experiments conducted to test the efficacy of regorafenib combined with DIN showed dramatic tumor inhibitory effects due to induction of apoptosis. Our results suggested that the level of cyclin E1 expression in HCCs may be used as a pharmacodynamic biomarker to assess the antitumor effects of regorafenib or sorafenib.

Conclusions

Combining regorafenib and CDK inhibitors may enhance the clinical efficiency of the treatment of HCCs.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0398-3) contains supplementary material, which is available to authorized users.

MEK Inhibition Targets Cancer Stem Cells and Impedes Migration of Pancreatic Cancer Cells In Vitro and In Vivo

Pancreatic ductal adenocarcinoma (PDAC) remains a devastating disease with a very poor prognosis. At the same time, its incidence is on the rise, and PDAC is expected to become the second leading cause of cancer-related death by 2030. Despite extensive work on new therapeutic approaches, the median overall survival is only 6-12 months after diagnosis and the 5-year survival is less than 7%. While pancreatic cancer is particularly difficult to treat, patients usually succumb not to the growth of the primary tumor, but to extensive metastasis; therefore, strategies to reduce the migratory and metastatic capacity of pancreatic cancer cells merit close attention. The vast majority of pancreatic cancers harbor RAS mutations. The outstanding relevance of the RAS/MEK/ERK pathway in pancreatic cancer biology has been extensively shown previously. Due to their high dependency on Ras mutations, pancreatic cancers might be particularly sensitive to inhibitors acting downstream of Ras. Herein, we use a genetically engineered mouse model of pancreatic cancer and primary pancreatic cancer cells were derived from this model to demonstrate that small-molecule MEK inhibitors functionally abrogate cancer stem cell populations as demonstrated by reduced sphere and organoid formation capacity. Furthermore, we demonstrate that MEK inhibition suppresses TGFβ-induced epithelial-to-mesenchymal transition and migration in vitro and ultimately results in a highly significant reduction in circulating tumor cells in mice.

Encorafenib inhibits migration, induces cell cycle arrest and apoptosis in colorectal cancer cells

Encorafenib, a new-generation BRAF inhibitor, has been approved by FDA for the treatment of melanoma in combination with binimetinib. However, the mechanism of the drug works in colorectal cancer (CRC) is still unclear. In this study, the suppression of growth of CRC cells by encorafenib was investigated. The effects of treatment of encorafenib on pathways linked to cancer were studied, and the effective inhibition of cell proliferation was documented. Our findings showed that cell migration was inhibited by encorafenib through a likely involvement of MPP and TIMP modulation. Furthermore, encorafenib treatment also induced cell cycle arrest. In addition, induction of apoptosis in CRC cells by elevating levels of PUMA. These observations indicate the potential therapeutic efficacy of encorafenib on CRC.

Short-term 3D culture systems of various complexity for treatment optimization of colorectal carcinoma

Three-dimensional (3D) cultures have the potential to increase the predictive value of pre-clinical drug research and bridge the gap towards anticipating clinical outcome of proposed treatments. However, their implementation in more advanced drug-discovery programs is still in its infancy due to the lack of reproducibility and low time- and cost effectiveness. HCT116, SW620 and DLD1 cells, cell lines with distinct mutations, grade and origin, were co-cultured with fibroblasts and endothelial cells (EC) in 3D spheroids. Clinically relevant drugs, i.e. 5-fluorouracil (5−FU), regorafenib and erlotinib, were administered individually to in CRC cell cultures. In this study, we established a robust, low-cost and reproducible short-term 3D culture system addressing the various complexities of the colorectal carcinoma (CRC) microenvironment. We observed a dose-dependent increase of erlotinib sensitivity in 3D (co-)cultures compared to 2D cultures. Furthermore, we compared the drug combination efficacy and drug-drug interactions administered in 2D, 3D and 3D co-cultures. We observed that synergistic/additive drug-drug interactions for drug combinations administered at low doses shifted towards additive and antagonistic when applied at higher doses in metastatic CRC cells. The addition of fibroblasts at various ratios and EC increased the resistance to some drug combinations in SW620 and DLD1 cells, but not in HCT116. Retreatment of SW620 3D co-cultures with a low-dose 3-drug combination was as active (88% inhibition, relative to control) as 5-FU treatment at high dose (100 μM). Moreover, 3D and 3D co-cultures responded variably to the drug combination treatments, and also signalling pathways were differently regulated, probably due to the influence of fibroblasts and ECs on cancer cells. The short-term 3D co-culture system developed here is a powerful platform for screening (combination) therapies. Understanding of signalling in 3D co-cultures versus 3D cultures and the responses in the 3D models upon drug treatment might be beneficial for designing anti-cancer therapies.

Regorafenib induces lethal autophagy arrest by stabilizing PSAT1 in glioblastoma

GBM (glioblastoma multiforme) is the most common and aggressive brain tumor with no curative options available. Therefore, it is imperative to develop novel potent therapeutic drugs for GBM treatment. Here, we show that regorafenib, an oral multi-kinase inhibitor, exhibits superior therapeutic efficacy over temozolomide, the first-line chemotherapeutic agent for GBM treatment both in vitro and in vivo. Mechanistically, regorafenib directly stabilizes PSAT1 (phosphoserine aminotransferase 1), a critical enzyme for serine synthesis, to trigger PRKAA-dependent autophagy initiation and inhibit RAB11A-mediated autophagosome-lysosome fusion, resulting in lethal autophagy arrest in GBM cells. Maintenance of PSAT1 at a high level is essential for regorafenib-induced GBM suppression. Together, our data provide novel mechanistic insights of regorafenib-induced autophagy arrest and suggest a new paradigm for effective treatment of GBM.Abbreviations: 3-MA: 3-methyladenine; ACACA: acetyl coenzyme A carboxylase alpha; ACTB/β-actin: actin, beta; AMPK: adenosine monophosphate-activated protein kinase; ATG5: autophagy related 5; CTSD: cathepsin D; DN-: dominant-negative; GBM: glioblastoma multiforme; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PRKAA/AMPKα: protein kinase AMP-activated catalytic subunit alpha; PSAT1: phosphoserine aminotransferase 1; SQSTM1/p62: sequestosome 1; TKIs: tyrosine kinase inhibitors.