Echinomycin as a promising therapeutic agent against KSHV-related malignancies.

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of several human cancers, including Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL), which preferentially arise in immunocompromised patients while lack of effective therapeutic options. Oncoproteins Myc and hypoxia-inducible factor-1α (HIF1α) have been found closely related to KSHV infection, replication and oncogenesis. However, the strategies of dual targeting these two oncoproteins have never been developed and tested for treatments of KSHV-related malignancies. In the current study, we report that treatment of echinomycin dramatically regresses cell growth both in vitro-cultured KSHV + tumor cells and in vivo KS or PEL xenograft mice models, through simultaneously inhibiting Myc and HIF1α expression. Echinomycin treatment also induces viral lytic gene expression whereas not increasing infectious virions production from KSHV + tumor cells. Our comparative transcriptomic analysis has identified a bunch of new Echinomycin-regulated, Myc- and HIF1α-related genes contributed to KSHV pathogenesis, including KDM4B and Tau, which are required for the survival of KSHV + tumor cells with functional validation. These data together reveal that dual targeting Myc and HIF1α such as using Echinomycin may represent a new and promising option for treatments of these virus-associated malignancies.

Hypoxia-inducible factor 1α inhibitor induces cell death via suppression of BCR-ABL1 and Met expression in BCR-ABL1 tyrosine kinase inhibitor sensitive and resistant chronic myeloid leukemia cells.

Chronic myeloid leukemia (CML) has a markedly improved prognosis with the use of breakpoint cluster region-abelson 1 (BCR-ABL1) tyrosine kinase inhibitors (BCR-ABL1 TKIs). However, approximately 40% of patients are resistant or intolerant to BCR-ABL1 TKIs. Hypoxia-inducible factor 1α (HIF-1α) is a hypoxia response factor that has been reported to be highly expressed in CML patients, making it a therapeutic target for BCR-ABL1 TKI-sensitive CML and BCR-ABL1 TKI-resistant CML. In this study, we examined whether HIF-1α inhibitors induce cell death in CML cells and BCR-ABL1 TKI-resistant CML cells. We found that echinomycin and PX-478 induced cell death in BCR-ABL1 TKIs sensitive and resistant CML cells at similar concentrations while the cell sensitivity was not affected with imatinib or dasatinib in BCR-ABL1 TKIs resistant CML cells. In addition, echinomycin and PX-478 inhibited the c-Jun N-terminal kinase (JNK), Akt, and extracellular-regulated protein kinase 1/2 (ERK1/2) activation via suppression of BCR-ABL1 and Met expression in BCR-ABL1 sensitive and resistant CML cells. Moreover, treatment with HIF-1α siRNA induced cell death by inhibiting BCR-ABL1 and Met expression and activation of JNK, Akt, and ERK1/2 in BCR-ABL1 TKIs sensitive and resistant CML cells. These results indicated that HIF-1α regulates BCR-ABL and Met expression and is involved in cell survival in CML cells, suggesting that HIF-1α inhibitors induce cell death in BCR-ABL1 TKIs sensitive and resistant CML cells and therefore HIF-1α inhibitors are potential candidates for CML treatment. [BMB Reports 2023; 56(2): 78-83].

Pharmacological or genetic inhibition of hypoxia signaling attenuates oncogenic RAS-induced cancer phenotypes.

Oncogenic Ras mutations are highly prevalent in hematopoietic malignancies. However, it is difficult to directly target oncogenic RAS proteins for therapeutic intervention. We have developed a Drosophila acute myeloid leukemia model induced by human KRASG12V, which exhibits a dramatic increase in myeloid-like leukemia cells. We performed both genetic and drug screens using this model. The genetic screen identified 24 candidate genes able to attenuate the oncogenic RAS-induced phenotype, including two key hypoxia pathway genes HIF1A and ARNT (HIF1B). The drug screen revealed that echinomycin, an inhibitor of HIF1A, can effectively attenuate the leukemia phenotype caused by KRASG12V. Furthermore, we showed that echinomycin treatment can effectively suppress oncogenic RAS-driven leukemia cell proliferation, using both human leukemia cell lines and a mouse xenograft model. These data suggest that inhibiting the hypoxia pathway could be an effective treatment approach and that echinomycin is a promising targeted drug to attenuate oncogenic RAS-induced cancer phenotypes. This article has an associated First Person interview with the first author of the paper.

The HIF1α-PDGFD-PDGFRα axis controls glioblastoma growth at normoxia/mild-hypoxia and confers sensitivity to targeted therapy by echinomycin.

BACKGROUND: Glioblastoma multiforme (GBM), a lethal brain tumor, remains the most daunting challenge in cancer therapy. Overexpression and constitutive activation of PDGFs and PDGFRα are observed in most GBM; however, available inhibitors targeting isolated signaling pathways are minimally effective. Therefore, better understanding of crucial mechanisms underlying GBM is needed for developing more effective targeted therapies. METHODS: Target genes controlled by HIF1α in GBM were identified by analysis of TCGA database and by RNA-sequencing of GBM cells with HIF1α knockout by sgRNA-Cas9 method. Functional roles of HIF1α, PDGFs and PDGFRs were elucidated by loss- or gain-of-function assays or chemical inhibitors, and compared in response to oxygen tension. Pharmacological efficacy and gene expression in mice with intracranial xenografts of primary GBM were analyzed by bioluminescence imaging and immunofluorescence. RESULTS: HIF1α binds the PDGFD proximal promoter and PDGFRA intron enhancers in GBM cells under normoxia or mild-hypoxia to induce their expression and maintain constitutive activation of AKT signaling, which in turn increases HIF1α protein level and activity. Paradoxically, severe hypoxia abrogates PDGFRα expression despite enhancing HIF1α accumulation and corresponding PDGF-D expression. Knockout of HIF1A, PDGFD or PDGFRA in U251 cells inhibits cell growth and invasion in vitro and eradicates tumor growth in vivo. HIF1A knockdown in primary GBM extends survival of xenograft mice, whereas PDGFD overexpression in GL261 shortens survival. HIF1α inhibitor Echinomycin induces GBM cell apoptosis and effectively inhibits growth of GBM in vivo by simultaneously targeting HIF1α-PDGFD/PDGFRα-AKT feedforward pathway. CONCLUSIONS: HIF1α orchestrates expression of PDGF-D and PDGFRα for constitutive activation of AKT pathway and is crucial for GBM malignancy. Therefore, therapies targeting HIF1α should provide an effective treatment for GBM.

HIF-1α inhibitor echinomycin reduces acute graft-versus-host disease and preserves graft-versus-leukemia effect.

BACKGROUND: Acute graft-versus-host disease (aGVHD) remains a major obstacle against favorable clinical outcomes following allogeneic hematopoietic stem cell transplantation (allo-HSCT). T helper cells including Th17 play key roles in aGVHD pathogenesis. Donor regulatory T cell (Tregs) adoptive therapy reduces aGVHD without weakening graft-versus-leukemia effect (GVL) in both mouse and human, although the purification and ex vivo expansion of Tregs in clinical scenarios remain costly and technically demanding. Hypoxia-inducible factor 1 alpha (HIF-1α) is a key molecule switch that attenuates Treg but promotes Th17 development. However, whether pharmacological inhibition of HIF-1α reduces aGVHD via increasing Treg development and diminishing Th17 responses remains unexplored. METHODS: By using alloantigen-specific mixed lymphocyte culture and murine models of aGVHD and GVL, we evaluated the impacts of HIF-1α inhibition by echinomycin on the alloantigen-specific CD4 T cell responses ex vivo, as well as on aGVHD and GVL effect following allo-HSCT. RESULTS: Ex vivo echinomycin treatment resulted in increased number of Tregs in the culture as well as reduced alloantigen-specific Th17 and Th1 responses. In vivo echinomycin treatment reduced GVHD scores and prolonged survival of mice following allo-HSCT, which is associated with increased number of donor Tregs and reduced number of Th17 and Th1 in lymphoid tissues. In murine model of leukemia, echinomycin treatment preserved GVL effect and prolonged leukemia free survival following allo-HSCT. CONCLUSIONS: Echinomycin treatment reduces aGVHD and preserves GVL effect via increasing donor Treg development and diminishing alloantigen-specific Th17 and Th1 responses following allo-HSCT, presumably via direct inhibition of HIF-1α that results in preferential Treg differentiation during alloantigen-specific CD4 T cell responses. These findings highlight pharmacological inhibition of HIF-1α as a promising strategy in GVHD prophylaxis.

Effects of the hypoxia-inducible factor-1 inhibitor echinomycin on vascular endothelial growth factor production and apoptosis in human ectopic endometriotic stromal cells.

Recent evidence points to a possible role for hypoxia-inducible factor (HIF)-1 in the pathogenesis and development of endometriosis. The objectives of this study were to investigate the critical role of HIF-1 in endometriosis and the effect of the HIF-1 inhibitor echinomycin on human ectopic endometriotic stromal cells (eESCs). Ectopic endometriotic tissues were obtained from 20 patients, who received an operation for ovarian endometriomas. We examined vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1 (SDF-1) production, HIF-1 expression, cell proliferation and apoptosis of eESCs. Cobalt chloride (CoCl2) significantly induced expression of HIF-1α protein and VEGF production in a time-dependent manner in eESCs, but reduced SDF-1 production. VEGF production was significantly suppressed by treatment of 100 nM echinomycin without causing cell toxicity, but 0.1-10 nM echinomycin or 100 nM progestin had no significant effect. SDF-1 production was not affected by echinomycin treatment at any dose. Echinomycin inhibited cell proliferation and induced apoptotic cell death of the eESCs, and significantly inhibited expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL. Echinomycin inhibits VEGF production and induces apoptosis of eESCs by suppression of Bcl-2 and Bcl-xL. These findings suggest the unique therapeutic potential for echinomycin as an inhibitor of HIF-1 activation for endometriosis treatment.

In vitro and in vivo activities of echinomycin against clinical isolates of Staphylococcus aureus.

OBJECTIVES: To verify in vitro and in vivo activities of echinomycin against clinical isolates of Staphylococcus aureus, we compared antistaphylococcal activities of echinomycin with those of vancomycin. METHODS: In vitro activities (MICs and MBCs) of oxacillin, vancomycin and echinomycin against 18 isolates of methicillin-susceptible S. aureus (MSSA) and 118 isolates of methicillin-resistant S. aureus (MRSA) were compared. Using four representative isolates of S. aureus, time-kill assay and in vivo antistaphylococcal activities were assessed. Echinomycin and vancomycin were compared in an in vivo mouse infection model. RESULTS: Echinomycin demonstrated higher in vitro activities against MSSA and MRSA strains, exhibiting 2-fold lower MIC(90)s and 4-fold lower MBC(90)s than vancomycin. Additionally, time-kill assay indicated that echinomycin is more potent than vancomycin against MSSA and MRSA strains in the context of MICs and MBCs. Using an in vivo protection model, it was shown that the 50% effective doses of echinomycin were at least 7-fold lower than those of vancomycin. Therefore, echinomycin displayed excellent protection in mice against acute peritoneal infections caused by both MSSA and MRSA strains. CONCLUSIONS: Collectively, these data indicate that the activity of echinomycin against S. aureus strains is at least equivalent to that of vancomycin, regardless of the methicillin resistance of these strains. These promising activities of echinomycin might justify its potential use against infections with S. aureus strains resistant to vancomycin. This might be the first report to show that echinomycin possesses antipathogenic staphylococcal activity.

A new antitumor agent: methyl sulfonium perchlorate of echinomycin.

Newly modified-echinomycin such as S-methylated sulfonium perchlorate of echinomycin (1), monosulfoxide (2), disulfoxid (3) and sulfone (4) have been prepared and evaluated for in vitro biological activities of cytotoxicity against P388, B16 and SNU-16 as well as in vivo antitumor activity against murine leukemia P388 and melanoma B16.

A phase II clinical trial of echinomycin in metastatic soft tissue sarcoma. An Illinois Cancer Center Study.

Echinomycin, a cyclic peptide in the family of quinoxaline antibiotics, was evaluated in patient with metastatic, soft tissue sarcoma not previously treated for metastatic disease. The starting dose of echinomycin was 1,200 mcg/m2 administered intravenously, once weekly x 4, followed by a two-week break. The protocol design called for dose escalation on subsequent cycles of therapy, but because of significant toxicity, dose escalation occurred in only 5 of 25 treatment cycles. Severe nausea and vomiting was the most common toxicity. No clinical responses were observed in the 12 evaluable patients. Echinomycin at this dose and schedule is inactive in metastatic soft tissue sarcoma.

Phase II trial of echinomycin in patients with advanced or recurrent colorectal cancer.

Echinomycin is a novel bifunctional intercalating agent derived from Streptomyces echinatus. A phase II clinical trial of echinomycin in patients with advanced, measurable colorectal cancer was initiated to determine the efficacy and toxicities of this agent. Echinomycin, 1.5 mg/m2, was given initially as a 30- to 60-min infusion every 4 weeks. After 4 episodes of anaphylaxis had occurred among the first 14 patients, the schedule was changed to a 24-h infusion, and an additional 16 patients were treated on this schedule. Treatment was given every 3 weeks. A total of 30 patients were eligible and evaluable; there were 3 (10%; 90% confidence interval, 3%-23%) clinical responses lasting 3, 3+, and 12 months, respectively. The most serious toxicity encountered was anaphylaxis, which occurred in 5 patients, although with no serious sequelae. A premedication regimen with dexamethasone, diphenhydramine, and cimetidine and a change of the duration of the infusion to 24 h reduced the incidence of this complication. Grade 2-3 vomiting occurred among earlier patients treated; however, with the 24-h schedule this toxicity was substantially reduced. The sole important case of hematologic toxicity was a single patient with grade 3 thrombocytopenia. Echinomycin employed in this dose and schedule had modest activity against colorectal cancer, comparable with that observed with 5-fluorouracil. Further studies in patients with gastrointestinal malignancies using a 24-h infusion with a dexamethasone premedication regimen similar to that employed prior to administration of taxol may be warranted.

Phase II study of echinomycin in the treatment of renal cell carcinoma ECOG study E2885.

Seventeen patients were treated with echinomycin for metastatic renal cell carcinoma. Echinomycin is a bifunctional DNA intercalating agent with broad preclinical antitumor activity. It was given at 1200 mg/m2 by intravenous infusion over 30-60 min weekly for 4 weeks. The treatment was repeated every 6 weeks. There were no responses observed in the study. No life threatening or lethal toxicity was documented in 13 eligible patients. The median survival of these patients was 13.7 months. We conclude that echinomycin is not active against metastatic renal cell carcinoma at the dose and schedule tested.

Echinomycin in recurrent and metastatic endometrial carcinoma. A phase II trial of the Gynecologic Oncology Group.

Twenty-one evaluable patients with recurrent or metastatic endometrial carcinoma were treated with 1,500 micrograms/m2 of echinomycin every 3 weeks. All patients had received prior chemotherapy. There was one complete response (5%), 95% confidence interval for response is 0.9-22.7%. The major toxicity was nausea and vomiting which was moderate to severe in 42% of patients. Myelosuppression was minimal. Echinomycin, in this dose and schedule, displays minimal activity in patients with advanced endometrial carcinoma who have had prior chemotherapy.

Phase II trial of echinomycin for the treatment of advanced renal cell carcinoma. A Southwest Oncology Group study.

Forty-nine patients with metastatic or recurrent renal cell carcinoma were treated on a phase II trial of Echinomycin. Treatment consisted of Echinomycin 1.25 mg/m2 intravenously every 28 days. Among the 47 evaluable patients there were no complete responses and only one partial response for an overall response rate of 2% (95% confidence interval, 0-11%). Eighteen patients (38%) experienced toxicity of grade 3 or worse. The most common toxicities were nausea and vomiting. The results of this study indicate that Echinomycin is not sufficiently active to warrant further trials for the treatment of renal cell carcinoma.

Phase II evaluation of echinomycin (NSC-526417) in patients with central nervous system malignancies. A Southwest Oncology Group study.

The objective of this trial was to determine the efficacy of echinomycin (1.2 mg/m2) administered on a weekly times four schedule in the treatment of patients with recurrent or progressive central nervous malignancies despite adequate radiotherapy. Thirty-five patients were registered on study. The majority of patients (20) had glioblastoma multiforme. Ten had anaplastic astrocytoma. Eight patients had received prior nitrosoureas. SWOG performance status was 1 in 11 patients and 2 in 22. The median age was 51 years (25-75 years). One patient had a partial remission (3%:95% confidence interval: 1%-16%). Twenty two patients had progressive disease. The median survival was 5.9 months. Toxicity was primarily gastrointestinal with nausea and vomiting in 13 patients and nausea only in 11 patients. Hepatotoxicity occurred in 10 patients. Echinomycin given at this dose and schedule is not effective in treating patients with recurrent or progressive glioblastoma multiforme or anaplastic astrocytomas.

Echinomycin (NSC 526417) in recurrent and metastatic nonsquamous cell carcinoma of the cervix. A phase II trial of the Gynecologic Oncology Group.

Eighteen evaluable patients with recurrent or metastatic nonsquamous carcinoma of the uterine cervix were treated with 1,500 micrograms/m2 of echinomycin every 4 weeks. Seven patients had received prior chemotherapy. There was one complete response (5.6%), 95% confidence interval for response of 0-27%. The major toxicity was nausea and vomiting, which was moderate to severe in eight patients. Myelosuppression was minimal. Echinomycin in this dose and schedule displays minimal activity in patients with advanced nonsquamous carcinoma of the cervix.

Phase II study of echinomycin in patients with advanced breast cancer: a report of Cancer and Leukemia Group B protocol 8641.

Twenty-five women with advanced histologically documented stage IV recurrent or inoperable breast cancer were enrolled on a phase II study of echinomycin administered at a dose of 1.2 mg/m2 intravenously over 30 minutes weekly for 4 weeks followed by a two week rest period. Seventy-six percent of patients had visceral dominant disease at study entry and all patients had previously received chemotherapy. One of 21 eligible patients had a partial response lasting 147 days. The median survival for this group of patients was 5.9 months and the median time to treatment failure was 1.7 months. Nausea and vomiting was the primary toxic effect and was severe or life-threatening in 43% of patients. Transient elevation of liver enzymes occurred in 30% of patients. Bone marrow suppression was not significant. Echinomycin as employed in this study did not demonstrate significant antitumor activity in previously treated patients with advanced breast cancer.

Phase II trial of echinomycin in advanced soft tissue sarcomas. A Southwest Oncology Group study.

Thirty-four patients with advanced soft tissue sarcomas were entered in a phase II trial of echinomycin. Patients received 1.2 mg/m2 intravenously (i.v.) weekly times four followed by a two week rest period. There were no objective responses. Dose limiting toxicity was gastrointestinal. Echinomycin given on this weekly schedule is inactive in treating previously treated patients with advanced soft tissue sarcomas.