Hypoxia-Inducible Factor 1alpha- Mediated Resistance to Phenolic Anticancer

Hypoxia-Inducible Factor-Dependent and Independent Mechanisms Underlying Chemoresistance of Hypoxic Cancer Cells

In hypoxic regions of malignant solid tumors, cancer cells acquire resistance to conventional therapies, such as chemotherapy and radiotherapy, causing poor prognosis in patients with cancer. It is widely recognized that some of the key genes behind this are hypoxia-inducible transcription factors, e.g., hypoxia-inducible factor 1 (HIF-1). Since HIF-1 activity is suppressed by two representative 2-oxoglutarate-dependent dioxygenases (2-OGDDs), PHDs (prolyl-4-hydroxylases), and FIH-1 (factor inhibiting hypoxia-inducible factor 1), the inactivation of 2-OGDD has been associated with cancer therapy resistance by the activation of HIF-1. Recent studies have also revealed the importance of hypoxia-responsive mechanisms independent of HIF-1 and its isoforms (collectively, HIFs). In this article, we collate the accumulated knowledge of HIF-1-dependent and independent mechanisms responsible for resistance of hypoxic cancer cells to anticancer drugs and briefly discuss the interplay between hypoxia responses, like EMT and UPR, and chemoresistance. In addition, we introduce a novel HIF-independent mechanism, which is epigenetically mediated by an acetylated histone reader protein, ATAD2, which we recently clarified.

Oncofetal reprogramming in tumor development and progression: novel insights into cancer therapy

Emerging evidence indicates that cancer cells can mimic characteristics of embryonic development, promoting their development and progression. Cancer cells share features with embryonic development, characterized by robust proliferation and differentiation regulated by signaling pathways such as Wnt, Notch, hedgehog, and Hippo signaling. In certain phase, these cells also mimic embryonic diapause and fertilized egg implantation to evade treatments or immune elimination and promote metastasis. Additionally, the upregulation of ATP-binding cassette (ABC) transporters, including multidrug resistance protein 1 (MDR1), multidrug resistance-associated protein 1 (MRP1), and breast cancer-resistant protein (BCRP), in drug-resistant cancer cells, analogous to their role in placental development, may facilitate chemotherapy efflux, further resulting in treatment resistance. In this review, we concentrate on the underlying mechanisms that contribute to tumor development and progression from the perspective of embryonic development, encompassing the dysregulation of developmental signaling pathways, the emergence of dormant cancer cells, immune microenvironment remodeling, and the hyperactivation of ABC transporters. Furthermore, we synthesize and emphasize the connections between cancer hallmarks and embryonic development, offering novel insights for the development of innovative cancer treatment strategies.

Hypoxia in the Initiation and Progression of Neuroblastoma Tumours

Neuroblastoma is the most frequent extracranial solid tumour in children, causing 10% of all paediatric oncology deaths. It arises in the embryonic neural crest due to an uncontrolled behaviour of sympathetic nervous system progenitors, giving rise to heterogeneous tumours. Low local or systemic tissue oxygen concentration has emerged as a cellular stimulus with important consequences for tumour initiation, evolution and progression. In neuroblastoma, several evidences point towards a role of hypoxia in tumour initiation during development, tumour cell differentiation, survival and metastatic spreading. However, the heterogeneous nature of the disease, its developmental origin and the lack of suitable experimental models have complicated a clear understanding of the effect of hypoxia in neuroblastoma tumour progression and the molecular mechanisms implicated. In this review, we have compiled available evidences to try to shed light onto this important field. In particular, we explore the effect of hypoxia in neuroblastoma cell transformation and differentiation. We also discuss the experimental models available and the emerging alternatives to study this problem, and we present hypoxia-related therapeutic avenues being explored in the field.

Resveratrol: its biologic targets and functional activity

The polyphenolic phytoalexin resveratrol (RSV) and its analogues have received tremendous attention over the past couple of decades because of a number of reports highlighting their benefits in vitro and in vivo in a variety of human disease models, including cardio- and neuroprotection, immune regulation, and cancer chemoprevention. These studies have underscored the high degree of diversity in terms of the signaling networks and cellular effector mechanisms that are affected by RSV. The activity of RSV has been linked to cell-surface receptors, membrane signaling pathways, intracellular signal-transduction machinery, nuclear receptors, gene transcription, and metabolic pathways. The promise shown by RSV has prompted heightened interest in studies aimed at translating these observations to clinical settings. In this review, we present a comprehensive account of the basic chemistry of RSV, its bioavailability, and its multiple intracellular target proteins and signaling pathways.

Synthesis of novel trans-stilbene derivatives and evaluation of their potent antioxidant and neuroprotective effects

A convenient synthesis and the biological properties of new amides, esters and other derivatives of trans-stilbene are described. The key synthetic strategies involve the Wittig-Horner reaction of a phosphonium salt 9 and an aldehyde 10 to generate (E)- or (Z)-olefins and a coupling reaction of an acid 12 and various amines 13a-n to give trans-stilbene derivatives 15a-n in high yields. A amide derivative 15g showed three times more in vitro free radical-scavenging activity than resveratrol, while another 15d exhibited strong inhibitory activity against lipopolysaccharide (LPS)(a)-induced NO generation. Allylamide analogue 15a showed the most potent neuroprotective activity in glutamate-induced primary cortical neuron cells.

Efficacy of pentavalent antimony, amphotericin B, and miltefosine in Leishmania amazonensis-infected macrophages under normoxic and hypoxic conditions

Recently, our group demonstrated that mouse lesions infected with Leishmania amazonensis are hypoxic. Evidence indicates the negative impact of hypoxia on the efficacy of a variety of chemotherapeutic agents against tumors, fungi, bacteria, and malaria parasites. In the present study, comparison of the effect of antileishmanial drugs on L. amazonensis-infected macrophages under normoxic and hypoxic conditions was performed. We compared the effect of 5% oxygen tension with a tension of 21% oxygen on peritoneal murine macrophage cultures infected with the parasite and treated with glucantime, amphotericin B, or miltefosine. Analysis of the infection index (percentage of infected macrophages x number of amastigotes per macrophage), dose-dependent efficacy of drugs, and IC(50) values demonstrated that hypoxia conferred a small, but significant, resistance to all 3 antileishmanial drugs. The present finding suggests that in vitro assays under hypoxia should not be neglected in drug studies.

New approaches to pharmacotherapy of tumors of the nervous system during childhood and adolescence

Tumors of the nervous system are among the most common and most chemoresistant neoplasms of childhood and adolescence. Malignant tumors of the brain collectively account for 21% of all cancers and 24% of all cancer-related deaths in this age group. Neuroblastoma, a peripheral nervous system tumor, is the most common extracranial solid tumor of childhood, and 65% of children with this tumor have only a 10 or 15% chance of living 5 years beyond the time of initial diagnosis. Novel pharmacological approaches to nervous system tumors are urgently needed. This review presents the role of and current challenges to pharmacotherapy of malignant tumors of the nervous system during childhood and adolescence and discusses novel approaches aimed at overcoming these challenges.

Hypoxia-inducible factor-1 alpha contributes to hypoxia-induced chemoresistance in gastric cancer

Hypoxia induced drug resistance is a major obstacle in the development of effective cancer therapy. Our previous study revealed that hypoxia-inducible factor-1 (HIF-1), the major transcriptional factor significantly activated by hypoxia, was overexpressed in gastric vincristine-resistant cells SGC7901/vincristine (VCR) under normoxic conditions, which suggested that it was associated with drug resistance in gastric cancer cells. In the present study, a colony-forming assay revealed that hypoxia and forced HIF-1 alpha expression increased maximal -8.9-fold or -14.8-fold of IC(50) toward vincristine in gastric cancer cell lines SGC7901 and SGC7901/VCR, respectively (P < 0.01). Annexin-V/propidium iodide staining analysis revealed hypoxia or forced HIF-1 alpha expression reduced apoptosis by 24% or 18% in SGC7901 cells (P < 0.05). Flow cytometry analysis of intracellular adriamycin revealed that hypoxia and forced expression of HIF-1 alpha increased -1.79-fold or -2.36-fold of the adriamycin releasing index, respectively (P < 0.05). However, resistance acquisition subject to hypoxia in vitro and in vivo was suppressed by blocking HIF-1 alpha expression with siRNA. We further demonstrated that HIF-1 alpha overexpression showed a 1.85-fold increased expression of Bcl-2 and a 2.16-fold decreased expression of Bax, and also showed significantly induced expression of p-gp and MRP1, which indicated that HIF-1 alpha may confer hypoxia-induced drug resistance via inhibition of drug-induced apoptosis and decreases in intracellular drug accumulation.