Double immunohistochemical staining method for HIF-1alpha and its regulators PHD2 and PHD3 in formalin-fixed paraffin-embedded tissues

Multiplex Immunofluorescence Staining Protocol for the Dual Imaging of Hypoxia-Inducible Factors 1 and 2 on Formalin-Fixed Paraffin-Embedded Samples

Hypoxia is a common condition in rapidly proliferating tumors and occurs when oxygen delivery to the tissue is scarce. It is a prevalent feature in ~90% of solid tumors. The family of HIF (hypoxia-inducible factor) proteins-HIF1α and HIF2α-are the main transcription factors that regulate the response to hypoxia. These transcription factors regulate numerous downstream gene targets that promote the aggressiveness of tumors and therefore have been linked to worse prognosis in patients. This makes them a potential biomarker to be tested in the clinical setting to predict patient outcomes. However, HIFs have been notoriously challenging to immunolabel, in part due to their fast turnover under normal oxygen conditions. In this work, we developed a multiplexed immunofluorescence (mIF) staining protocol for the simultaneous detection of HIF1α and HIF2α in the same formalin-fixed paraffin-embedded (FFPE) tissue section.

Increased expression of LAT1 in basal cell carcinoma - implications for tumour cell survival

BACKGROUND

Basal cell carcinoma (BCC) is the most common type of cancer in fair-skinned individuals worldwide. Altered metabolism is a hallmark of cancer, and a growing body of evidence has shown increased expression of the large neutral amino acid transporter (LAT) small subunit 1 in several types of cancers, including BCC. However, the mechanisms behind changed LAT1 expression in BCC are largely unknown.

OBJECTIVES

To describe the protein expression of LAT1 and its co-localisation with LAT2, and to examine LAT1 in association with BCC tumour biology characteristics such as cell proliferation, apoptosis, and hypoxia.

METHODS

Formalin-fixed and paraffin-embedded tissue samples (n=14) from excised BCCs were stained with immunofluorescence and examined regarding protein-staining patterns.

RESULTS

There was no correlation between expression of LAT1 and LAT2, and the co-localisation was low. The proliferation markers topoisomerase IIα and Ki-67 both showed a significantly higher expression in the BCC tissue than in the normal epidermis (p=0.0063 and p=0.010, respectively). The fraction of LAT1-expressing cells in the BCC was inversely correlated to the fraction of proliferative active tumour cells (p=0.0013). Cleaved caspase-3 was significantly increased in tumour areas with high LAT1 expression (p=0.016).

CONCLUSIONS

The findings of the present study show that LAT1 is not usually expressed by proliferating BCC cells. The morphological localisation suggests that tumour cells use LAT1 in adaption to environmental changes such as starvation and/or hypoxia. These findings could have implications for future development of LAT1-inhibitory BCC treatments.

Selenium targets resistance biomarkers enhancing efficacy while reducing toxicity of anti-cancer drugs: preclinical and clinical development

Selenium (Se)-containing molecules exert antioxidant properties and modulate targets associated with tumor growth, metastasis, angiogenesis, and drug resistance. Prevention clinical trials with low-dose supplementation of different types of Se molecules have yielded conflicting results. Utilizing several xenograft models, we earlier reported that the enhanced antitumor activity of various chemotherapeutic agents by selenomethione and Se-methylselenocysteine in several human tumor xenografts is highly dose- and schedule-dependent. Further, Se pretreament offered selective protection of normal tissues from drug-induced toxicity, thereby allowing higher dosing than maximum tolerated doses. These enhanced therapeutic effects were associated with inhibition of hypoxia-inducible factor 1- and 2-alpha (HIF1α, HIF2α) protein, nuclear factor (erythyroid-derived 2)-like 2 (Nrf2) and pair-related homeobox-1 (Prx1) transcription factors, downregulation of oncogenic- and upregulation of tumor suppressor miRNAs. This review provides: 1) a brief update of clinical prevention trials with Se; 2) advances in the use of specific types, doses, and schedules of Se that selectively modulate antitumor activity and toxicity of anti-cancer drugs; 3) identification of targets selectively modulated by Se; 4) plasma and tumor tissue Se levels achieved after oral administration of Se in xenograft models and cancer patients; 5) development of a phase 1 clinical trial with escalating doses of orally administered selenomethionine in sequential combination with axitinib to patients with advanced clear cell renal cell carcinoma; and 6) clinical prospects for future therapeutic use of Se in combination with anticancer drugs.

Constitutive expression of HIF-α plays a major role in generation of clear-cell phenotype in human primary and metastatic renal carcinoma

The extensive lipid accumulation occurring in clear-cell renal cell carcinoma (ccRCC) results in a clear-cell cytoplasm. Hypoxia-inducible factor α (HIF-α) is constitutively expressed in many ccRCC and transcriptionally regulates >100 genes. In a recent breakthrough study, HIF-1α induced ccRCC in transgenic mice. On the basis of these findings, we developed a hypothesis that accounted for HIF-α generation of the clear-cell phenotype. The aim of the present study was to use immunohistochemical staining methods in tissue microarray to determine the extent to which the clear-cell phenotype coincided with HIF-α expression in primary and metastatic ccRCC. In addition, we studied whether the prolyl-hydroxylases (PHD2,3) play a role in promoting the elevated expression of HIF-α in tumor cells. The clear-cell phenotype was observed in all primary and metastatic cases of ccRCC examined. A total of 168 renal cell carcinomas were evaluated by immunohistochemical methods; 141 of the 168 (84%) tumors expressed HIF-α (HIF-1α and/or HIF-2α). In contrast, HIF-α was expressed in only 1 of the 23 (4%) non-ccRCCs. These data supported the hypothesis that in the majority of the tumors HIF-α expression overlapped with the clear-cell phenotype and was indicative of an HIF-α-mediated lipid accumulation. In a smaller percentage of ccRCC cases (16%), HIF-α was not detected in the tumor cells and suggested that lipid accumulation by HIF-α-lipid-independent process. PHD3 was undetectable in both primary and metastatic ccRCC cases. We concluded that the undetectable PHD3 could contribute to the higher HIF-α expression in ccRCC.

Nicotinic modulation of therapeutic response in vitro and in vivo

Tobacco use significantly increases the risk of developing cancer. Moreover, there is growing evidence that tobacco use decreases survival in cancer patients. Nicotine, a systemically available component of tobacco, is associated with tumor promotion and decreased apoptosis in cell culture; however, the role of nicotine on response to radiotherapy (RT) or chemoradiotherapy (CRT) in vivo has not been evaluated. Our study evaluated the effects of nicotine administration on cancer cell survival in cell culture and mouse models. Nicotine increased survival in two cell lines following RT in vitro. Nicotine administration in mice during fractionated RT or CRT increased xenograft regrowth as compared to RT or CRT alone. Nicotine increased hypoxia-inducible factor 1-alpha (HIF-1α) expression in tumor xenografts without altering expression of carbonic-anhydrase, a clinical marker of tumor hypoxia. The effects of nicotine on HIF-1α expression were transient, returning to baseline levels within 2-3 days after nicotine removal. Further mechanistic studies indicated that inhibition of phosphoinositide-3-kinase (PI3K) prevented nicotine-mediated increases in HIF-1α expression as well as the prosurvival effects of nicotine on RT. These findings imply that during tobacco use, nicotine may function as a systemic agent through acute and reversible regulation of HIF-1α expression and a decreased therapeutic response.

Prolyl hydroxylase 2 dependent and Von-Hippel-Lindau independent degradation of Hypoxia-inducible factor 1 and 2 alpha by selenium in clear cell renal cell carcinoma leads to tumor growth inhibition

Background

Clear cell renal cell carcinoma (ccRCC) accounts for more than 80% of the cases of renal cell carcinoma. In ccRCC deactivation of Von-Hippel-Lindau (VHL) gene contributes to the constitutive expression of hypoxia inducible factors 1 and 2 alpha (HIF-α), transcriptional regulators of several genes involved in tumor angiogenesis, glycolysis and drug resistance. We have demonstrated inhibition of HIF-1α by Se-Methylselenocysteine (MSC) via stabilization of prolyl hydroxylases 2 and 3 (PHDs) and a significant therapeutic synergy when combined with chemotherapy. This study was initiated to investigate the expression of PHDs, HIF-α, and VEGF-A in selected solid cancers, the mechanism of HIF-α inhibition by MSC, and to document antitumor activity of MSC against human ccRCC xenografts.

Methods

Tissue microarrays of primary human cancer specimens (ccRCC, head & neck and colon) were utilized to determine the incidence of PHD2/3, HIF-α, and VEGF-A by immunohistochemical methods. To investigate the mechanism(s) of HIF-α inhibition by MSC, VHL mutated ccRCC cells RC2 (HIF-1α positive), 786–0 (HIF-2α positive) and VHL wild type head & neck cancer cells FaDu (HIF-1α) were utilized. PHD2 and VHL gene specific siRNA knockdown and inhibitors of PHD2 and proteasome were used to determine their role in the degradation of HIF-1α by MSC.

Results

We have demonstrated that ccRCC cells express low incidence of PHD2 (32%), undetectable PHD3, high incidence of HIF-α (92%), and low incidence of VEGF-A compared to head & neck and colon cancers. This laboratory was the first to identify MSC as a highly effective inhibitor of constitutively expressed HIF-α in ccRCC tumors. MSC did not inhibit HIF-1α protein synthesis, but facilitated its degradation. The use of gene knockdown and specific inhibitors confirmed that the inhibition of HIF-1α was PHD2 and proteasome dependent and VHL independent. The effects of MSC treatment on HIF-α were associated with significant antitumor activity against ccRCC xenograft.

Conclusions

Our results show the role of PHD2/3 in stable expression of HIF-α in human ccRCC. Furthermore, HIF-1α degradation by MSC is achieved through PHD2 dependent and VHL independent pathway which is unique for HIF-α regulation. These data provide the basis for combining MSC with currently used agents for ccRCC.

The prognostic value of expression of HIF1α, EGFR and VEGF-A, in localized prostate cancer for intermediate- and high-risk patients treated with radiation therapy with or without androgen deprivation therapy

Purpose

Androgens stimulate the production of hypoxia-inducible factor (HIF1α) and ultimately vascular endothelial growth factor (VEGF-A). Additionally, epithelial growth factor (EGF) mediates HIF1α production. Carbonic anhydrase IX (CAIX) expression is associated with tumor cell hypoxia in a variety of malignancies. This study assesses the prognostic relation between HIF1α, VEGF-A, EGF Receptor and CAIX expression by immunochemistry in diagnostic samples of patients with intermediate- and high-risk localized prostate cancer treated with radiation therapy, with or without androgen deprivation therapy (ADT).

Materials and methods

Between 1994 and 2004, 103 prostate cancer patients (mean age, 68.7 ± 6.2), with prostate cancer (mean PSA, 13.3 ± 3.7), were treated with radiation therapy (RT, median dose, 74 Gy). Fifty seven (55.3%) patients received ADT (median duration, 6 months; range, 0 – 24). Median follow-up was 97.6 months (range, 5.9 – 206.8).

Results

Higher EGFR expression was significantly (p = 0.04) correlated with higher Gleason scores. On univariate analysis, HIF1α nuclear expression was a significant (p = 0.02) prognostic factor for biological progression-free survival (bPFS). A trend towards significance (p = 0.05) was observed with EGFR expression and bPFS. On multivariate analysis, low HIF1α nuclear (p = 0.01) and high EGFR (p = 0.04) expression remained significant adverse prognostic factors.

Conclusions

Our study suggests that high nuclear expression of HIF1α and low EGFR expression in diagnostic biopsies of prostate cancer patients treated with RT ± ADT is associated with a good prognosis.

Architectural heterogeneity in tumors caused by differentiation alters intratumoral drug distribution and affects therapeutic synergy of antiangiogenic organoselenium compound

Tumor differentiation enhances morphologic and microvascular heterogeneity fostering hypoxia that retards intratumoral drug delivery, distribution, and compromise therapeutic efficacy. In this study, the influence of tumor biologic heterogeneity on the interaction between cytotoxic chemotherapy and selenium was examined using a panel of human tumor xenografts representing cancers of the head and neck and lung along with tissue microarray analysis of human surgical samples. Tumor differentiation status, microvessel density, interstitial fluid pressure, vascular phenotype, and drug delivery were correlated with the degree of enhancement of chemotherapeutic efficacy by selenium. Marked potentiation of antitumor activity was observed in H69 tumors that exhibited a well-vascularized, poorly differentiated phenotype. In comparison, modulation of chemotherapeutic efficacy by antiangiogenic selenium was generally lower or absent in well-differentiated tumors with multiple avascular hypoxic, differentiated regions. Tumor histomorphologic heterogeneity was found prevalent in the clinical samples studied and represents a primary and critical physiological barrier to chemotherapy.