Hypoxia signaling: Challenges and opportunities for cancer therapy

Hypoxia is arguably the first recognized cancer microenvironment hallmark and affects virtually all cellular populations present in tumors. During the past decades the complex adaptive cellular responses to oxygen deprivation have been largely elucidated, raising hope for new anti cancer agents. Despite undeniable preclinical progress, therapeutic targeting of tumor hypoxia is yet to transition from bench to bedside. This review focuses on new pharmacological agents that exploit tumor hypoxia or interfere with hypoxia signaling and discusses strategies to maximize their therapeutic impact.

Regulation of cellular sterol homeostasis by the oxygen responsive noncoding RNA lincNORS

We hereby provide the initial portrait of lincNORS, a spliced lincRNA generated by the MIR193BHG locus, entirely distinct from the previously described miR-193b-365a tandem. While inducible by low O₂ in a variety of cells and associated with hypoxia in vivo, our studies show that lincNORS is subject to multiple regulatory inputs, including estrogen signals. Biochemically, this lincRNA fine-tunes cellular sterol/steroid biosynthesis by repressing the expression of multiple pathway components. Mechanistically, the function of lincNORS requires the presence of RALY, an RNA-binding protein recently found to be implicated in cholesterol homeostasis. We also noticed the proximity between this locus and naturally occurring genetic variations highly significant for sterol/steroid-related phenotypes, in particular the age of sexual maturation. An integrative analysis of these variants provided a more formal link between these phenotypes and lincNORS, further strengthening the case for its biological relevance.

The Many Faces of Long Noncoding RNAs in Cancer

SIGNIFICANCE

The emerging connections between an increasing number of long noncoding RNAs (lncRNAs) and oncogenic hallmarks provide a new twist to tumor complexity. Recent Advances: In the present review, we highlight specific lncRNAs that have been studied in relation to tumorigenesis, either as participants in the neoplastic process or as markers of pathway activity or drug response. These transcripts are typically deregulated by oncogenic or tumor-suppressing signals or respond to microenvironmental conditions such as hypoxia.

CRITICAL ISSUES

Among these transcripts are lncRNAs sufficiently divergent between mouse and human genomes that may contribute to biological differences between species.

FUTURE DIRECTIONS

From a translational standpoint, knowledge about primate-specific lncRNAs may help explain the reason behind the failure to reproduce the results from mouse cancer models in human cell-based systems. Antioxid. Redox Signal. 29, 922-935.

Abstract C6: Molecular and cellular signaling of PDGFB in cervical cancer cells

Cervical cancer was reported to be the second most common female cancer worldwide, being the third cause of female cancer mortality annually. Romania ranks first among European countries in cervical cancer incidence and mortality raising the national awareness. Cervical cancer is one of the most aggressive gynecological diseases, mainly is due to rapid development of a functional tumor vascular network.

In solid tumors, PDGF signalling has been showed to participate in processes such as autocrine stimulation of tumor cell growth, recruitment of tumor stroma and stimulation of angiogenesis. PDGF signaling increases the interstitial fluid pressure, an important drawback in drug administration due to loss of active agents before they reach the tumors. Several studies have showed that targeting PDGF pathways have anti-angiogenic and anti-tumor effects, implying that inhibition of PDGF signaling may improve the efficacy of chemotherapies. However, these studies have been focused on effects on tumor vasculature and mural cells, and less on tumor cells. Moreover, the molecular mechanisms of PDGF signaling in tumor cells have yet to be investigated.

Here we report the molecular and cellular effects of PDGFb inhibition of in cervical tumor cells. We used the RNA interference pathway to trigger PDGFb silencing in two HPV16 positive cervical cancer cell lines (Hela, Caski). We investigated the changes in genes expression induced by PDGFb silencing by means of microarray analysis. Transcriptomic analysis revealed 579 genes to be differentially expressed upon PDGFb silencing. Among the top biological functions regulated by these genes are Cell Death and Survival, Cellular Growth and Proliferation, Cardiovascular System Development and Function, Cellular Movement, etc. Cellular investigations on proliferation, apoptosis, and invasion revealed that PDGFb silencing had no effects on cells ability to proliferate nor induced cell death, which suggest that alternative signaling mechanisms are activated to maintain the balance between cell proliferation and apoptosis. This is probably done throughout HPV16 signaling as some of the identified genes are known to be involved in viral infections. We did however observe that PDGFb silencing reduced the invasiveness of cervical cancer cells. Although preliminary, our results could explain the short-term success of antiangiogenic therapies.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C6.

Citation Format: Oana M. Tudoran, Olga Soritau, Ovidiu Balacescu, Loredana Balacescu, Staffan Lindberg, Ioana Berindan-Neagoe. Molecular and cellular signaling of PDGFB in cervical cancer cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C6.