Tracey J. Brown

A crucial requirement for Hedgehog signaling in small cell lung cancer

Small-cell lung cancer (SCLC) is an aggressive neuroendocrine subtype of lung cancer for which there is no effective treatment. Using a mouse model in which deletion of Rb1 and Trp53 in the lung epithelium of adult mice induces SCLC, we found that the Hedgehog signaling pathway is activated in SCLC cells independently of the lung microenvironment. Constitutive activation of the Hedgehog signaling molecule Smoothened (Smo) promoted the clonogenicity of human SCLC in vitro and the initiation and progression of mouse SCLC in vivo. Reciprocally, deletion of Smo in Rb1 and Trp53-mutant lung epithelial cells strongly suppressed SCLC initiation and progression in mice. Furthermore, pharmacological blockade of Hedgehog signaling inhibited the growth of mouse and human SCLC, most notably following chemotherapy. These findings show a crucial cell-intrinsic role for Hedgehog signaling in the development and maintenance of SCLC and identify Hedgehog pathway inhibition as a therapeutic strategy to slow the progression of disease and delay cancer recurrence in individuals with SCLC.

Antisense-Mediated Suppression of Hyaluronan Synthase 2 Inhibits the Tumorigenesis and Progression of Breast Cancer

The progression of several cancers is correlated with the increased synthesis of the glycosaminoglycan, hyaluronan. Hyaluronan is synthesized at the plasma membrane by various isoforms of hyaluronan synthases (HAS). The importance of HAS2 expression in highly invasive breast cancer was characterized by the antisense inhibition of HAS2 (ASHAS2). The effect of HAS2 inhibition on cell proliferation, migration, hyaluronan metabolism, and receptor status was characterized in vitro, whereas the effect on tumorigenicity and metastasis was established in vivo. HAS2 inhibition resulted in a 24-hour lag in proliferation that was concomitant to transient arrest of 79% of the cell population in G0-G1. Inhibition of HAS2 did not alter the expression of the other HAS isoforms, whereas hyaluronidase (HYAL2) and the hyaluronan receptor, CD44, were significantly down-regulated. ASHAS2 cells accumulated greater amounts of high molecular weight hyaluronan (>10,000 kDa) in the culture medium, whereas mock and parental cells liberated less hyaluronan of three distinct molecular weights (100, 400, and 3,000 kDa). The inhibition of HAS2 in the highly invasive MDA-MB-231 breast cancer cell line inhibited the initiation and progression of primary and secondary tumor formation following s.c. and intracardiac inoculation into nude mice, whereas controls readily established both primary and secondary tumors. The lack of primary and secondary tumor formation was manifested by increased survival times where ASHAS2 animals survived 172% longer than the control animals. Collectively, these unique results strongly implicate the central role of HAS2 in the initiation and progression of breast cancer, potentially highlighting the co-dependency between HAS2, CD44, and HYAL2 expression.

Silencing of hyaluronan synthase 2 suppresses the malignant phenotype of invasive breast cancer cells

Accumulation of hyaluronan has been demonstrated in the peritumoral breast cancer stroma and nests of tumor cells. In this study, we have quantified the production of hyaluronan and the expression of mRNAs encoding hyaluronan synthesizing (HAS) and hyaluronan degrading (HYAL) enzymes in a panel of breast cancer cell lines. The analysis revealed that highly invasive breast cancer cells produce high amounts of hyaluronan and express preferentially HAS2 mRNA, whereas less invasive breast cancer cells produce low amount of hyaluronan and express HAS1 and HYAL1 mRNAs. We explored the importance of HAS2 expression for breast cancer tumorigenicity, by specifically silencing the HAS2 gene using RNA interference (RNAi)‐mediated suppression in the invasive breast cancer cell line Hs578T. This led to a less aggressive phenotype of the breast tumor cells, as assessed by cell growth, both in anchorage‐dependent and anchorage‐independent cultures. siRNA‐mediated knock down of HAS2 in Hs578T breast tumor cells led to an up‐regulation of HAS1, HAS3 and HYAL1 mRNAs, resulting in only a 50% decrease in the net hyaluronan production; however, the synthesized hyaluronan was of lower size and more polydisparse compared to control siRNA‐treated cells. Interestingly, Hs578T cells deprived of HAS2 migrated only half as efficiently as HAS2 expressing cells through cell‐free areas in a culture wounding assay and through Transwell polycarbonate membrane as well as invaded a Matrigel layer. These results imply that alterations in HAS2 expression and endogenously synthesized hyaluronan affect the malignant phenotype of Hs578T breast cancer cells.

A new disorder of hyaluronan metabolism associated with generalized folding and thickening of the skin

OBJECTIVE To describe and characterize a new disorder of hyaluronan metabolism associated with marked abnormalities of cutaneous tissue and to determine whether a relationship with a phenotypically similar disorder in the shar-pei dog exists. METHODS Biopsy specimens of the skin of a child with extreme cutaneous thickening and folding were examined by light and electron microscopy. The concentration of hyaluronan and the activity of hyaluronidase were measured in the patients serum and plasma, respectively, and the activity of hyaluronan synthase was examined in cultured dermal fibroblasts. Hyaluronan concentration was also measured in the plasma of 23 shar-pei and 34 control dogs. RESULTS The patients skin displayed gross accumulation of hyaluronan, and the serum concentration of hyaluronan was markedly elevated (up to 3100 microg/L) during infancy. Hyaluronan synthase activity of cultured dermal fibroblasts was increased, whereas hyaluronidase activity in plasma was normal (5.5 +/- 0.08 IU/L). Plasma hyaluronan concentration was higher in the shar-pei dogs than in control dogs (median, 378 microg/L vs 73 microg/L, respectively). CONCLUSION The child we describe has a novel disorder of hyaluronan metabolism, which appears to result from abnormal control of hyaluronan synthesis. An analogous disorder may be present in the shar-pei dog.

THE HISTOCHEMICAL STRUCTURE OF THE DEEP FASCIA AND ITS STRUCTURAL RESPONSE TO SURGERY

The histochemical structure of the deep fascia and its interface with the underlying muscle was examined in ten pigs. This structure was also evaluated after it had been raised as a fascial flap and in another site after the underlying muscle surface had been disrupted. The deep fascial is a simple structure of densely-packed collagen bundles and elastin fibres, and has hyaluronic acid concentrated on its inner surface, which is in contact with the underlying muscle. There is no specialised lining of this surface of the fascia to account for its gliding properties. The post-surgical specimens demonstrated preservation of the structure of the interface between fascia and muscle, including the retention of the hyaluronic acid lining, if the epimysium was intact. However, if the epimysium was disrupted, the structure of the interface was obliterated.

The prognostic significance of aldehyde dehydrogenase 1A1 (ALDH1A1) and CD133 expression in early stage non-small cell lung cancer

Background Expression of aldehyde dehydrogenase 1A1 (ALDH1A1) and CD133 has been functionally associated with a stem cell phenotype in normal and malignant cells. The prevalence of such cells in solid tumours should therefore correlate with recurrence and/or metastasis following definitive surgical resection. The aim of this study was to evaluate the prognostic significance of ALDH1A1 and CD133 in surgically resected, early stage non-small cell lung cancer (NSCLC). Methods A retrospective analysis of ALDH1A1 and CD133 expression in 205 patients with pathologic stage I NSCLC was performed using immunohistochemistry. The association between the expression of both markers and survival was determined. Results We identified 62 relapses and 58 cancer-related deaths in 144 stage 1A and 61 stage 1B patients, analysed at a median of 5-years follow-up. Overexpression of ALDH1A1 and CD133, detected in 68.7% and 50.7% of primary tumours, respectively, was an independent prognostic indicator for overall survival by multivariable Cox proportional hazard model (p=0.017 and 0.039, respectively). Overexpression of ALDH1A1, but not of CD133, predicted poor recurrence-free survival (p=0.025). When categorised into three groups according to expression of ALDH1A1/CD133, patients with overexpression of both ALDH1A1 and CD133 belonged to the group with the shortest recurrence-free and overall survival (p=0.015 and 0.017, respectively). Conclusions Expression of ALDH1A1 and CD133, and coexpression of ALDH1A1 and CD133, is strongly associated with poor survival in early-stage NSCLC following surgical resection. These data are consistent with the hypothesis that expression of stem cell markers correlates with recurrence as an indirect measure of self-renewal capacity.

Phase I and pharmacokinetic evaluation of intravenous hyaluronic acid in combination with doxorubicin or 5-fluorouracil

Background: Pre-clinically, hyaluronan (HA) has been demonstrated to systemically target chemotherapeutic drugs to tumours while ameliorating treatment toxicities. This study is a preliminary clinical investigation to determine if HA could be safely used in combination with 5-fluorouracil (5-FU) and doxorubicin (DOX). Methods: Thirty patients with metastatic cancer were intravenously administered 500 mg/m2 HA in combination with escalating doses of DOX (30–60 mg/m2) or 5-FU (cumulative dose of 1,350–2,250 mg/m2 per cycle). The effect of pre-administration of 20 mg/m2 of folinic acid on HA/5-FU chemotherapy was also investigated. Patients were randomized to receive either HA/chemotherapy or chemotherapy alone in their first treatment cycle and vice versa for the second cycle. Patients received HA and chemotherapy in all subsequent cycles. Results:Treatment was well tolerated, tumour responses were observed and the co-administration of HA did not alter the pharmacokinetics of clinically relevant doses of 5-FU or DOX. Conclusion:High doses of intravenous high-molecular-weight HA can be safely co-administered with clinical doses of chemotherapy without significantly altering the toxicity or pharmacokinetics of the drugs or HA.

The development of hyaluronan as a drug transporter and excipient for chemotherapeutic drugs.

Despite advances in chemotherapeutic regimens, the treatment of metastatic cancer remains a challenge. A key problem with chemotherapy drugs is nonspecific drug distribution, resulting in low tumor concentrations and systemic toxicity. The holy grail of clinical cancer research has been to establish more specific ways of directing therapeutics to tumors, whether through more targeted anti-cancer agents or via the method of delivery. Many tumor cells show up-regulated expression of receptors for the polysaccharide hyaluronan (HA), resulting in HA having a high affinity for tumors. This observation has led to the preclinical development of HA-cytotoxin bioconjugates that utilize HA as the tumor recognition moiety. The primary challenges have been organ-directed toxicity and limited efficacy. An alternative, simpler strategy has been to use the large volumetric domain of HA to entrain small chemotherapeutic drugs within the HA matrix. The resultant HA/drug formulation accumulates in the microvascular of the tumor, forming a microembolism that increases drug retention at the tumor site and allows for active tumor uptake through HA receptors. Clinical trials of HA formulations of three anti-cancer drugs have been undertaken and have demonstrated that such formulations are safe and efficacious. Within these formulations we postulate that HA is acting as a novel excipient, capable of improving the therapeutic index of the active anti-cancer agent.

A pilot human evaluation of a formulation of irinotecan and hyaluronic acid in 5-fluorouracil-refractory metastatic colorectal cancer patients.

Background: Preclinical data demonstrate that the polysaccharide hyaluronic acid (HA) acts as a macromolecular carrier for chemotherapeutic drugs. In these studies the formulation of HA and irinotecan reduced treatment-related toxicity and improved efficacy via the preferential delivery of irinotecan to the tumor and lymph nodes. This study was designed as a first-in-man investigation of the safety and pharmacokinetics of irinotecan when administered within the HA-Irinotecan formulation. Methods: 5-Fluorouracil refractory metastatic colorectal cancer patients were intravenously treated with HA-Irinotecan (300 mg/m2 irinotecan with 1,000 mg/m2 HA) on day 1 of a 21-day cycle. After safety was demonstrated, the irinotecan dose was increased to 350 mg/m2 with maintenance of the HA at 1,000 mg/m2.DELETEResults: Twelve patients were treated with HA-Irinotecan. Overall toxicity was low, with an 8 and 17% incidence of grade lll/lV diarrhea and neutropenia, respectively. No grade III/IV nausea or vomiting was observed. Seventeen percent of patients had a partial response and 50% experienced stable disease, indicating that the efficacy of the irinotecan was maintained. Median survival was 16.6 months, while median progression-free survival was 6.2 months. Conclusion: HA-Irinotecan containing standard doses of irinotecan can be safely administered to patients. Comparison to historical irinotecan data suggests HA-Irinotecan may have a greater margin of safety without compromising anticancer activity.

Next-Generation Sequence Analysis of Cancer Xenograft Models

Next-generation sequencing (NGS) studies in cancer are limited by the amount, quality and purity of tissue samples. In this situation, primary xenografts have proven useful preclinical models. However, the presence of mouse-derived stromal cells represents a technical challenge to their use in NGS studies. We examined this problem in an established primary xenograft model of small cell lung cancer (SCLC), a malignancy often diagnosed from small biopsy or needle aspirate samples. Using an in silico strategy that assign reads according to species-of-origin, we prospectively compared NGS data from primary xenograft models with matched cell lines and with published datasets. We show here that low-coverage whole-genome analysis demonstrated remarkable concordance between published genome data and internal controls, despite the presence of mouse genomic DNA. Exome capture sequencing revealed that this enrichment procedure was highly species-specific, with less than 4% of reads aligning to the mouse genome. Human-specific expression profiling with RNA-Seq replicated array-based gene expression experiments, whereas mouse-specific transcript profiles correlated with published datasets from human cancer stroma. We conclude that primary xenografts represent a useful platform for complex NGS analysis in cancer research for tumours with limited sample resources, or those with prominent stromal cell populations.