Hypoxia-induced resistance to anticancer drugs is associated with decreased senescence and requires hypoxia-inducible factor-1 activity

Abstract

Hypoxia in solid tumors is associated with the development of chemoresistance. Although many studies have focused on the effect of hypoxia on drug-induced apoptosis, the effect of nonapoptotic pathways on hypoxia-induced drug resistance has not been previously investigated. Here, we determined the effects of hypoxia on multiple forms of drug-induced death in human MDA-MB-231 breast carcinoma cells. Clonogenic assays showed that preexposure to hypoxia leads to resistance to various classes of chemotherapeutic agents, including anthracyclines (daunorubicin and doxorubicin), epipodophyllotoxins (etoposide), and anthracenediones (mitoxantrone). Results revealed a high degree of heterogeneity in nuclear and cytoplasmic alterations in response to acute drug exposure; however, the majority of exposed cells displayed morphologic and biochemical changes consistent with drug-induced senescence. Hypoxia decreased only the proportion of cells in the senescent population, whereas the small proportion of cells exhibiting features of apoptosis or mitotic catastrophe were unaffected. Similar results were obtained with human HCT116 colon carcinoma cells, indicating that the protective effect of hypoxia on drug-induced senescence is not unique to MDA-MB-231 cells. Treatment of MDA-MB-231 cells with small interfering RNA targeting the A-subunit of hypoxiainducible factor-1 (HIF-1), a key regulator of cellular adaptations to hypoxia, prevented hypoxia-induced resistance. HIF-1A small interfering RNA also selectively abolished the hypoxia-induced changes in the senescent population, indicating that the increased survival was due to protection against drug-induced senescence. These results support a requirement for HIF-1 in the adaptations leading to drug resistance and reveal that decreased druginduced senescence is also an important contributor to the development of hypoxia-induced resistance.

Validation of the type 1 insulin-like growth factor receptor as a therapeutic target in renal cancer

“…There are several factors that could contribute to this effect. HIF1-α is known to mediate resistance to cytotoxic drugs, at least in part due to a reduction in drug-induced senescence (32,33). However, the effects of IGF1R depletion documented here must presumably have been HIF-independent, because 786-0 cells lack HIF1-α, and express only HIF2-α, which is not IGF-regulated in these cells (Fig.…”

ARF1 controls proliferation of breast cancer cells by regulating the retinoblastoma protein

“…For example, retinoic acid treatment first induced a slower cell growth rate between days 4 and 6, a decrease in cell number between day 6 and 9, and finally detectable SA-b-gal activity at day 8 (Roninson and Dokmanovic, 2003). Furthermore, senescence was also demonstrated in MDA-MB-231 cells (Sullivan et al, 2008;Bartholomew et al, 2009). In our experiments, SA-b-gal activity could be detected as soon as 4 days post transfection to reach a maximum at day 7.…”

Hypoxia Enhances Sphingosine Kinase 2 Activity and Provokes Sphingosine-1-Phosphate-Mediated Chemoresistance in A549 Lung Cancer Cells

“…HIF-1 is activated to support the development and progression of tumors by releasing proangiogenic and proproliferative cytokines and/or growth factors (3,36,37). Another characteristic feature of cancer cells is their resistance toward chemotherapeutic agents, a process that can be promoted by intratumoral hypoxia (2,8).…”

“…To circumvent periods of insufficient nutrient and oxygen supply, cells evolve mechanisms to adapt to such conditions, with the notion that hypoxia-inducible factor-1 (HIF-1) appears of particular importance. HIF-1 regulates the expression of >70 target genes, including proapoptotic ones (4), but also provokes an antiapoptotic phenotype of tumor cells (5)(6)(7)(8). In addition, there are HIF-1-independent pathways that promote cell survival under hypoxia by activating, for example, phosphoinositide 3-kinase (PI3K) or extracellular signalregulated kinase 1/2 [p42/44 mitogen-activated protein kinase (MAPK; ref.…”