Feasibility and outcomes of partial nephrectomy for resection of at least 20 tumors in a single renal unit

PURPOSE

Patients with hereditary renal cancer are at increased risk for recurrent bilateral multifocal tumors and may require aggressive nephron sparing surgery to prevent renal replacement therapy. We evaluated feasibility and outcomes in patients who underwent partial nephrectomy with removal of at least 20 tumors in a single renal unit at 1 setting.

MATERIALS AND METHODS

We retrospectively reviewed the records of 30 patients who underwent a total of 34 partial nephrectomies with removal of at least 20 tumors at our institution from 1993 to 2008. Operative reports and hospital records were reviewed for perioperative data, and renal functional and oncologic outcomes. We compared preoperative and postoperative renal function with the 2-tailed t test.

RESULTS

There were no deaths and only 1 renal unit was lost. A median of 26.5 tumors was removed. Median estimated blood loss was 3,500 ml and median operative time was 9 hours. Perioperative complications developed in greater than 50% of cases. There was a statistically significant decrease in the estimated glomerular filtration rate at 3 months (67 vs 59 ml/minute/1.73 m(2), p < 0.001). Only 1 patient had metastatic disease. Eight of the 34 operated kidneys required subsequent intervention during the median followup of 52 months (range 4 to 187).

CONCLUSIONS

Aggressive partial nephrectomy to resect multiple tumors is technically feasible. There was a significant decrease in postoperative renal function but more than 80% of preoperative renal function was preserved in this cohort except in 1 patient. Also, oncologic outcomes were encouraging at intermediate term followup.

Inactivation of the FLCN tumor suppressor gene induces TFE3 transcriptional activity by increasing its nuclear localization

BACKGROUND

Germline mutations in a tumor suppressor gene FLCN lead to development of fibrofolliculomas, lung cysts and renal cell carcinoma (RCC) in Birt-Hogg-Dubé syndrome. TFE3 is a member of the MiTF/TFE transcription factor family and Xp11.2 translocations found in sporadic RCC involving TFE3 result in gene fusions and overexpression of chimeric fusion proteins that retain the C-terminal DNA binding domain of TFE3. We found that GPNMB expression, which is regulated by MiTF, was greatly elevated in renal cancer cells harboring either TFE3 translocations or FLCN inactivation. Since TFE3 is implicated in RCC, we hypothesized that elevated GPNMB expression was due to increased TFE3 activity resulting from the inactivation of FLCN.

METHODOLOGY/PRINCIPAL FINDINGS

TFE3 knockdown reduced GPNMB expression in renal cancer cells harboring either TFE3 translocations or FLCN inactivation. Moreover, FLCN knockdown induced GPNMB expression in FLCN-restored renal cancer cells. Conversely, wildtype FLCN suppressed GPNMB expression in FLCN-null cells. FLCN inactivation was correlated with increased TFE3 transcriptional activity accompanied by its nuclear localization as revealed by elevated GPNMB mRNA and protein expression, and predominantly nuclear immunostaining of TFE3 in renal cancer cells, mouse embryo fibroblast cells, mouse kidneys and mouse and human renal tumors. Nuclear localization of TFE3 was associated with TFE3 post-translational modifications including decreased phosphorylation.

CONCLUSIONS/SIGNIFICANCE

Increased TFE3 activity is a downstream event induced by FLCN inactivation and is likely to be important for renal tumor development. This study provides an important novel mechanism for induction of TFE3 activity in addition to TFE3 overexpression resulting from Xp11.2 translocations, suggesting that TFE3 may be more broadly involved in tumorigenesis.

Functional and oncologic outcomes of partial adrenalectomy for pheochromocytoma in patients with von Hippel-Lindau syndrome after at least 5 years of followup

PURPOSE

Although the safety and feasibility of partial adrenalectomy in patients with von Hippel-Lindau syndrome have been established, long-term outcomes have not been examined. In this study we evaluate the recurrence and functional outcomes in a von Hippel-Lindau syndrome cohort treated for pheochromocytoma with partial adrenalectomy with a followup of at least 5 years.

MATERIALS AND METHODS

We reviewed the records of patients with von Hippel-Lindau syndrome treated with partial adrenalectomy for pheochromocytoma at the National Cancer Institute. Demographic, germline mutation status, surgical indication, oncologic and functional outcome data were collected. Local recurrence was defined as radiographic evidence of recurrent tumor on the ipsilateral side of partial adrenalectomy. Patients were considered steroid dependent if they required steroids at most recent followup.

RESULTS

A total of 36 partial adrenalectomies for pheochromocytoma were performed in 26 patients with von Hippel-Lindau syndrome between September 1995 and December 2003. Of these cases 23 were performed open and 13 were performed laparoscopically. Prior surgical history was obtained for all patients. At a median followup of 9.25 years (range 5 to 46) metastatic pheochromocytoma had not developed in any patients. In 3 patients (11%) there were 5 local recurrences treated with surgical extirpation or active surveillance. All recurrences were asymptomatic and detected by radiographic imaging on followup. In addition, 3 of 26 patients (11%) subsequently required partial adrenalectomy for pheochromocytoma on the contralateral adrenal gland. In the entire cohort only 3 patients became steroid dependent (11%).

CONCLUSIONS

Outcomes of partial adrenalectomy in patients with von Hippel-Lindau syndrome with pheochromocytoma are encouraging at long-term followup and should be recommended as a primary surgical approach whenever possible. Adrenal sparing surgery can obviate the need for steroid replacement in the majority of patients. Local recurrence rates appear to be infrequent and can be managed successfully with subsequent observation or intervention.

Increasing reactive oxygen species as a therapeutic approach to treat hereditary leiomyomatosis and renal cell carcinoma

Hereditary leiomyomatosis renal cell carcinoma (HLRCC)-associated renal tumors are aggressive and tend to metastasize early. There are currently no effective forms of therapy for patients with advanced HLRCC-associated kidney cancer. We have previously shown that HLRCC cells express a high level of reactive oxygen species (ROS). In the present study we investigated the cytotoxic effects of increasing ROS level using bortezomib in combination with cisplatin on HLRCC cells in vitro and in an in vivo xenograft model. The cytotoxic effect of several ROS inducers on FH-deficient cells was assessed by synthetic lethality. ROS inducers had a pronounced impact on the viability of FH-deficient cells. Because of its high potency, the proteasome inhibitor bortezomib was further investigated. Bortezomib induced apoptosis in vitro in HLRCC cells and inhibited HLRCC tumour growth in vivo. Bortezomib-associated cytotoxicity was highly correlated with cellular ROS level: combining bortezomib with other ROS inducers enhanced cytotoxicity, while combining bortezomib with a ROS scavenger inhibited its cytotoxic effect. Finally, HLRCC murine xenografts were treated with bortezomib and cisplatin, another ROS inducer. This regimen induced HLRCC tumour regression in vivo. These findings suggest that increasing ROS level in HLRCC above a certain threshold can induce HLRCC-tumor cell death. Increasing tumor ROS with bortezomib in combination with cisplatin represents a novel targeted therapeutic approach to treat advanced HLRCC-associated renal tumors.

Contemporary clinical epidemiology of renal cell carcinoma: insight from a population based case-control study

PURPOSE

To clarify the contemporary clinical epidemiology of renal cell carcinoma we present trends in clinical presentation and treatment in patients enrolled in a population based case-control study.

MATERIALS AND METHODS

The National Cancer Institute performed a population based case-control study in metropolitan Detroit and Chicago from 2002 through 2007. In 1,136 patients with renal cell carcinoma who consented to an epidemiological interview and medical record review we ascertained detailed information on social and medical history, methods of renal cell carcinoma detection and diagnosis, cancer severity and treatment(s) received. From these data we assessed the demographic and cancer specific characteristics of study cases, and trends in clinical presentation, diagnosis and treatment.

RESULTS

Most patients with renal cell carcinoma had localized or regional tumors, including 52% with tumors 4 cm or less. The proportion of asymptomatic cases increased from 35% in 2002 to 50% in 2007 (p<0.001). Hypertension and diabetes were common in patients (58% and 17%, respectively) and 24% had at least 2 significant comorbid conditions at cancer diagnosis. While the use of laparoscopic surgery increased with time (p<0.001), fewer than 1/5 patients underwent nephron sparing surgery.

CONCLUSIONS

The proportion of patients presenting with small, asymptomatic renal cell carcinoma continues to increase. Most of these cases are still treated with radical nephrectomy, although increasingly via a laparoscopic approach. Since most patients with small renal cell carcinomas have 1 or more renal function relevant comorbidities, there is an imperative to increase the use of nephron sparing surgery.

Protein expression profiling in the spectrum of renal cell carcinomas

In this study, we aimed to evaluate the protein expression profile of a spectrum of renal cell carcinomas (RCC) to find potential biomarkers for disease onset and progression and therefore, prospective therapeutic targets. A 2D-gel based proteomic analysis was used to outline differences in protein levels among different subtypes of renal cell carcinomas, including clear cell carcinomas, papillary lesions, chromophobe tumors and renal oncocytomas. Spot pattern was compared to the corresponding normal kidney from the same patients and distinctive, differentially expressed proteins were characterized by mass spectrometry. Twenty-one protein spots were found differentially expressed between clear cell RCC and normal tissue and 38 spots were found expressed in chromophobe tumors. Eleven proteins were identified, with most differentially expressed -by fold change- between clear cell tumors and the corresponding normal tissue. Two of the identified proteins, Triosephosphate isomerase 1 (TPI-1) and Heat Shock protein 27 (Hsp27), were further validated in a separate set of tumors by immunohistochemistry and expression levels were correlated with clinicopathologic features of the patients. Hsp27 was highly expressed in 82% of the tumors used for validation, and all cases showed strong immunoreactivity for TPI-1. In both Hsp27 and TPI-1, protein expression positively correlated with histologic features of the disease. Our results suggest that the subjacent cytogenetic abnormalities seen in different histological types of RCC are followed by specific changes in protein expression. From these changes, Hsp27 and TPI-1 emerged as potential candidates for the differentiation and prognosis in RCC.

Consequences of adrenal venous sampling in primary hyperaldosteronism and predictors of unilateral adrenal disease

BACKGROUND

In patients with primary hyperaldosteronism, distinguishing between unilateral and bilateral adrenal hypersecretion is critical in assessing treatment options. Adrenal venous sampling (AVS) has been advocated by some to be the gold standard for localization of the responsible lesion, but there remains a lack of consensus for the criteria and the standardization of technique.

STUDY DESIGN

We performed a retrospective study of 114 patients with a biochemical diagnosis of primary hyperaldosteronism who all underwent CT scan and AVS before and after corticotropin (ACTH) stimulation. Univariate and multivariate analyses were performed to determine what factors were associated with AVS lateralization, and which AVS values were the most accurate criteria for lateralization.

RESULTS

Eighty-five patients underwent surgery at our institution for unilateral hyperaldosteronism. Of the 57 patients who demonstrated unilateral abnormalities on CT, AVS localized to the contralateral side in 5 patients and revealed bilateral hyperplasia in 6 patients. Of the 52 patients who showed bilateral disease on CT scan, 43 lateralized with AVS. The most accurate criterion on AVS for lateralization was the post-ACTH stimulation value. Factors associated with AVS lateralization included a low renin value, high plasma aldosterone-to plasma-renin ratio, and adrenal mass > or = 3 cm on CT scan.

CONCLUSIONS

Because 50% of patients would have been inappropriately managed based on CT scan findings, patients with biochemical evidence of primary hyperaldosteronism and considering adrenalectomy should have AVS. The most accurate measurement for AVS lateralization was the post-ACTH stimulation value. Although several factors predict successful AVS lateralization, none are accurate enough to perform AVS selectively.

Serum vascular endothelial growth factor-D prospectively distinguishes lymphangioleiomyomatosis from other diseases

OBJECTIVES

The majority of women with lymphangioleiomyomatosis (LAM) present with cystic lung disease, and most require lung biopsy for definitive diagnosis. The purpose of this study was to determine the prospective diagnostic usefulness of a serologic test for vascular endothelial growth factor-D (VEGF-D), a lymphangiogenic growth factor.

METHODS

We prospectively measured serum VEGF-D levels by enzyme-linked immunoassay in 48 women presenting with cystic lung disease. Diagnostic test performance was determined from a cohort of 195 women, with tuberous sclerosis complex (TSC), TSC-LAM, sporadic LAM (S-LAM), and other cystic lung diseases in the differential diagnosis, including biopsy-proven or genetically proven pulmonary Langerhans cell histiocytosis, emphysema, Sjögren syndrome, or Birt-Hogg-Dubé syndrome.

RESULTS

Serum VEGF-D levels were significantly greater in S-LAM (median 1,175 [interquartile range (IQR): 780-2,013] pg/mL; n = 56) than in other cystic lung diseases (median 281 [IQR 203-351] pg/mL; n = 44, P < .001). In the cohort evaluated prospectively, 12 of the 15 individuals ultimately diagnosed with LAM by biopsy had VEGF-D levels of > 800 pg/mL, whereas levels were < 600 pg/mL in all 18 subjects later diagnosed with other causes of cystic lung disease. Receiver operating characteristic curves demonstrated that VEGF-D effectively identified LAM, with an area under the curve of 0.961(95% CI, 0.923-0.992). A VEGF-D level of > 600 pg/mL was highly associated with a diagnosis of LAM (specificity 97.6%, likelihood ratio 35.2) and values > 800 pg/mL were diagnostically specific. Serum VEGF-D levels were significantly elevated in women with TSC-LAM (median 3,465 [IQR 1,970-7,195] pg/mL) compared with women with TSC only (median 370 [IQR 291-520] pg/mL), P < .001).

CONCLUSIONS

A serum VEGF-D level of > 800 pg/mL in a woman with typical cystic changes on high-resolution CT (HRCT) scan is diagnostically specific for S-LAM and identifies LAM in women with TSC. A negative VEGF-D result does not exclude the diagnosis of LAM. The usefulness of serum VEGF-D testing in men or in women who do not have cystic lung disease on HRCT scan is unknown.

Targeted therapies for non-clear renal cell carcinoma

The treatment of advanced and metastatic kidney cancer has been revolutionized by the development of targeted systemic therapies. Despite the growing number of available agents approved for use against clear cell renal cell carcinoma, patients with non-clear histologies, constituting approximately 1 in 4 cases of kidney cancer, have not received the same attention. The majority of clinical trials testing novel targeted therapies have excluded non-clear subtypes, providing limited therapeutic options for patients with these diagnoses and their oncologists. This review will focus on the use of targeted therapies against the non-clear histologic subtypes of renal cell carcinoma: papillary I and II, chromophobe, and collecting duct. The unique genetic and molecular profiles of each distinct non-clear kidney cancer subtype will be described, as these differences are integral to the development and effectiveness of the novel agents used to treat them. Trials focusing on non-clear kidney cancer, or those that treated clear cell tumors along with significant numbers of non-clear subtypes, will be discussed. The role of cytoreductive nephrectomy and the use of neoadjuvant and adjuvant targeted therapy will be reviewed. Lastly, areas of future research will be highlighted.

Partial adrenalectomy: underused first line therapy for small adrenal tumors

PURPOSE

Many patients with small adrenal masses undergo total adrenalectomy. We evaluated partial adrenalectomy outcomes by performing a comprehensive literature review.

MATERIALS AND METHODS

We performed a PubMed search of the English language literature using the queries partial adrenalectomy and adrenal sparing surgery, and identified 317 and 155 articles, respectively. We excluded case reports or series with fewer than 5 patients, articles not focused on surgical management and those that did not indicate perioperative outcomes. The remaining articles were cross-referenced by author and institution to eliminate studies with redundant cases. Demographics, diagnosis, tumor characteristics, perioperative and functional outcomes, and recurrence data were collected when available.

RESULTS

A total of 22 articles from a total of 22 first authors met our inclusion criteria, describing outcomes in a total of 417 patients. There has been an increasing trend toward partial adrenalectomy worldwide in the last 20 years. Partial adrenalectomy is most commonly done for Conn's syndrome, followed by pheochromocytoma. Most procedures are laparoscopic with minimal morbidity. The recurrence rate is only 3% and more than 90% of patients remain steroid independent.

CONCLUSIONS

Partial adrenalectomy surgical outcomes and perioperative complications are similar to those reported for total adrenalectomy. When partial adrenalectomy is done for small adrenal lesions, the malignancy rate is negligible, the recurrence rate is low and most patients remain steroid-free at long-term followup. These data strongly support the acceptance of partial adrenalectomy as first line treatment for small adrenal masses.

Oncological outcomes of partial nephrectomy for multifocal renal cell carcinoma greater than 4 cm

PURPOSE

Despite aggressive screening patients with hereditary renal cancers can present with large multifocal tumors. We present oncological outcomes in patients with hereditary renal cell carcinoma treated with partial nephrectomy for multifocal solid tumors with the largest lesion greater than 4 cm.

MATERIALS AND METHODS

Between 1995 and 2008 we identified 58 patients with hereditary renal cell carcinoma treated at our institution with partial nephrectomy for solid tumors greater than 4 cm. Data collected included demographic parameters, tumor size, pathological findings and laterality. Overall and metastasis-free survival was calculated based on information from the most recent followup evaluation and imaging.

RESULTS

The cohort included 41 patients (71%) with von Hippel-Lindau disease, 10 (17%) with Birt-Hogg-Dubé syndrome and 7 (11%) with hereditary papillary renal carcinoma. Mean age was 43.7 years (range 18 to 63) and mean largest tumor size was 5.3 cm (range 4 to 13). A mean of 6.4 kidney tumors (range 1 to 44) was resected. There was a predominance of nuclear grade 2 tumors (51 cases or 85%) and clear cell histology (44 or 73%), followed by papillary type I histology (7 or 11.7%). Overall and metastasis-free survival rates were 93% and 96.5%, respectively, at a median followup of 45 months (range 2 to 163).

CONCLUSIONS

Metastasis-free and overall survival of our patients is similar to that in the literature of those who undergo partial nephrectomy for T1B tumors in the sporadic population. Multifocality does not affect oncological outcomes at intermediate followup. Partial nephrectomy can be offered to patients with hereditary disease who present with multifocal tumors greater than 4 cm.

Tumor suppressor FLCN inhibits tumorigenesis of a FLCN-null renal cancer cell line and regulates expression of key molecules in TGF-beta signaling

Background

Germline mutations in the FLCN gene are responsible for the development of fibrofolliculomas, lung cysts and renal neoplasia in Birt-Hogg-Dube' (BHD) syndrome. The encoded protein folliculin (FLCN) is conserved across species but contains no classic motifs or domains and its function remains unknown. Somatic mutations or loss of heterozygosity in the remaining wild type copy of the FLCN gene have been found in renal tumors from BHD patients suggesting that FLCN is a classic tumor suppressor gene.

Results

To examine the tumor suppressor function of FLCN, wild-type or mutant FLCN (H255R) was stably expressed in a FLCN-null renal tumor cell line, UOK257, derived from a BHD patient. When these cells were injected into nude mice, tumor development was inversely dependent upon the level of wild-type FLCN expression. We identified genes that were differentially expressed in the cell lines with or without wild-type FLCN, many of which are involved in TGF-β signaling, including TGF-β2 (TGFB2), inhibin β A chain (INHBA), thrombospondin 1 (THBS1), gremlin (GREM1), and SMAD3. In support of the in vitro data, TGFB2, INHBA, THBS1 and SMAD3 expression levels were significantly lower in BHD-associated renal tumors compared with normal kidney tissue. Although receptor mediated SMAD phosphorylation was not affected, basal and maximal TGF-β-induced levels of TGFB2, INHBA and SMAD7 were dramatically reduced in FLCN-null cells compared with FLCN-restored cells. Secreted TGF-β2 and activin A (homo-dimer of INHBA) protein levels were also lower in FLCN-null cells compared with FLCN-restored cells. Consistent with a growth suppressive function, activin A (but not TGF-β2) completely suppressed anchorage-independent growth of FLCN-null UOK257 cells.

Conclusions

Our data demonstrate a role for FLCN in the regulation of key molecules in TGF-β signaling and confirm deregulation of their expression in BHD-associated renal tumors. Thus, deregulation of genes involved in TGF-β signaling by FLCN inactivation is likely to be an important step for tumorigenesis in BHD syndrome.

Abstract 5291: Exploring mechanisms underlying invasion in HLRCC: Assessing the contribution of HIF and ROS

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is a highly metastatic disease characterized by a disruption of the Krebs cycle due to a germline mutation of the fumarate hydratase gene (FH). We have recently shown that HLRCC kidney cancer cells are in a pseudo-hypoxic state due to normoxic stabilization of both HIF1 and HIF2 and that the expression of HIF1 can be decreased using ROS scavengers such as pyruvate or N-acetylcysteine (NAC). Our objective was to study the involvement on invasion of aberrant HIF1 and HIF2 expression in HLRCC cells. When either HIF1 or HIF2 was knocked down, invasion was dramatically inhibited in vitro. Invasion of HLRCC cells was also inhibited by decreasing the ROS level with NAC. To study further the mechanisms by which HIF1 and HIF2 mediate invasion in HLRCC, we evaluated several markers of glycolysis and ROS formation. Our results show that when HIF1, but not HIF2, is knocked down, Glut1 mRNA level, glucose uptake, and lactate secretion are decreased. Even though N-acetylcysteine treatment decreased HIF1 and HIF2 expression, it did not affect glucose uptake or lactate secretion by HLRCC cells. Moreover transient knock-down of HIF1 or HIF2 by siRNAs did not affect the ROS level in vitro. To study further the mechanism of action of both HIF1 and HIF2, microarrays and in vivo experiments with stably transfected cell lines with shRNA for HIF1, HIF2 and ARNT are in progress. These results suggest that HIF1-mediated invasion may partially involve glycolysis. The mechanisms by which HIF2 and ROS mediate invasion are still under study. Our data support the hypothesis that HIF1, HIF2 and ROS are important for invasion. If one of them is inhibited, invasiveness of the HLRCC cells is compromised.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5291.

Abstract 773: Identification and characterization of natural product-based inhibitors of hypoxia inducible factor-2 alpha

Clear cell renal cell carcinoma (RCC) is the most prevalent form of kidney cancer and is frequently associated with loss of von Hippel Lindau (VHL) gene function, resulting in the aberrant transcriptional activation of hypoxia response genes that contribute to tumor growth, angiogenesis and metastasis. Prior studies have shown that normoxic stabilization of hypoxia inducible factor (HIF)-1-alpha alone, while capable of mimicking some aspects of VHL loss, are not sufficient to reproduce tumorigenesis, indicating that it is not the most critical oncogenic substrate of VHL protein. To isolate compounds that selectively modulate HIF2-alpha for use as research tools and drug development leads, a cell-based high throughput screen of the NCI Natural Products Repository was performed. Stably transformed clones of the human renal clear cell carcinoma cell line 786-0 expressing a luciferase reporter construct under the control of the human vascular endothelial growth factor (VEGF) promoter-enhancer were used to identify natural product samples with inhibitory activity and minimal cellular toxicity. Leads from initial high throughput screen were chromatographically separated into component structures yielding several pure compounds with micromolar or submicromolar IC50 values, &gt;80% inhibition and &lt;5% cell toxicity. These compounds were then characterized biologically for their ability to inhibit VEGF protein secretion by intact 786-0 cells; several compounds showed &gt;90% inhibition of VEGF secretion at micromolar doses under normoxic conditions. Studies to establish HIF selectivity and effects on RCC cell proliferation, survival, motility and anchorage independent growth are underway.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 773.

Abstract LB-108: Glutamine addition and glucose addiction - linking metabolic abnormalities to genetic alterations in glioblastoma SF188 and hereditary leiomyomatosis renal carcinoma UOK262

Metabolic transformations of malignant cells are essential for tumor development and progression. Oncogene Akt and c-myc stimulate glucose metabolism and glutamine metabolism, respectively, and render the cancers dependent on glucose or glutamine for growth and survival (otherwise known as glucose addiction and glutamine addiction). However, many other oncogenes, tumor suppressor genes and signaling molecules also regulate glucose and glutamine metabolism, which results in various metabolic abnormalities in different cancers. The question we want to ask is how one or more genetic mutations can lead to the ultimate metabolic abnormalities of a given cancer. Toward this end, we report here the metabolic abnormalities of two human cancer cell lines, glioblastoma SF188, which is c-myc-dependent and is addicted to glutamine, and hereditary leiomyomatosis renal carcinoma (HLRCC) UOK262, which is fumarate hydratase-deficient and is addicted to glucose. We performed our metabolic analysis using the XF24 Extracellular Flux Analyzer and pharmacological modulators of cellular metabolism. The XF24 Analyzer simultaneously monitors oxygen consumption rate (OCR) and extracellular acidification rate (ECAR), which are indicators of mitochondrial respiration and aerobic glycolysis respectively. Oxygen consumption rate is also used as an indicator for the oxidation of glucose and glutamine when they are added to the cells after baseline measurement. We found that SF188 cells showed a small increase in acidification rate upon glucose addition, suggesting a relatively low basal glycolysis rate. We estimated the glycolytic capacity of the cells by determining the acidification rate after the addition of mitochondrial ATP syntase inhibitor oligomycin. The glycoltic capacity remained high although basal glycolysis rate was low. Glucose was not oxidized at all by these cells. Most importantly, we observed significant increases in oxygen consumption rate upon addition of glutamine indicating active uptake and oxidation of glutamine. Associated with active glutamine oxidation, SF188 cells exhibited high basal reparation rate and high respiratory capacity. Finally, SF188 cells grew and survived in medium containing glutamine but no glucose; however, they started to die in the medium containing glucose but no glutamine. In contrast with glioblastoma SF188, we found that HLRCC UOK262 cells exhibit high basal glycolysis rate, which is close to its maximal capacity. Interestingly, basal mitochondrial respiration and respiratory capacity are extremely low, which is associated with reported defective mitochondrial complex I. The growth and survival of UOK262 is dependent on a high concentration of glucose in the culture medium. Collectively, we established metabolic abnormalities of glioblastama SF188 and HLRCC UOK262, which contain genetic alterations in c-myc and fumarate hydratase, respectively, that makes them addicted to glutamine and glucose. The metabolic abnormalities we found include the preferential use of glucose and glutamine, the activation or inactivation of relevant enzymatic pathways that catabolize glucose and glutamine, and the modulation of mitochondrial bioenergetic activities in the two cancer cell lines. Most of cancer cell lines that we have studied showed metabolic abnormalities falling between the two extremes. Therefore, this type of metabolic analysis coupled with the analysis of genetic abnormalities in cancers will provides a rapid means to gain insight into the aberrant metabolism of each type of cancer and improve the efficacy of cancer therapy for a cancer with a particular set of metabolic abnormalities.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-108.

Abstract SY23-03: Oncogenic signal transduction via the hepatocyte growth factor/Met receptor kinase pathway

Signal Transduction via the hepatocyte growth factor (HGF)/Met receptor kinase pathway is critical for normal embryogenesis and adult homeostasis, and aberrant HGF/Met signaling contributes to tumorigenesis and metastasis in many prevalent forms of cancer. By defining the basic molecular mechanisms of pathway activation at the target cell surface, we hope to develop novel strategies to antagonize oncogenic signaling as well as methods to assess pathway status in cancer patients. These methods may help identify those most likely to benefit from HGF/Met targeted therapies and help monitor treatment response.

Distinct domains of HGF bind to the Met receptor tyrosine kinase and to cell-surface heparan sulfate (HS) proteoglycans. The latter are widely expressed, structurally diverse biopolymers that modulate many important protein-protein interactions, but their importance in eliciting HGF biological responses is controversial. We have identified basic (positively charged) amino acid residues in HGF that form the primary binding site for (negatively charged) HS proteoglycans. HS binding by these residues increases the affinity of ligand-receptor binding and, with HS polymers of sufficient length, facilitates ligand oligomerization. Ligand oligomerization, in turn, controls Met kinase activation, cell motility and proliferation under normal conditions. Opposite (negative) charge amino acid substitutions at these critical HS binding residues in HGF can mimic bound HS in promoting high affinity receptor binding, but antagonize the binding of long HS polymers on the cell surface, thereby antagonizing ligand oligomerization and its consequences. Engineering these substitutions in the context of a short HGF isoform containing only the primary HS and Met binding domains yields a potent and selective competitive inhibitor of oncogenic HGF signaling in vivo. These findings further define the role of HS in growth factor signaling and reveal a novel strategy for antagonist development that may be applicable to other HS-binding growth factors.

The Met receptor kinase is among many transmembrane proteins that are proteolytically released from the cell surface by a process known as ectodomain shedding. Consistent with the concept that Met ectodomain shedding is a normal physiological process, we found that healthy human volunteers (n &gt; 100) display soluble Met (sMet) plasma concentrations in the range of 100 - 300 ng/ml and urinary sMet concentrations that are approximately 1000-fold lower. We hypothesized that aberrantly high Met expression, a frequent occurrence in many forms of cancer, and/or dysregulated proteolytic activity, another common feature of aggressive malignancies, could lead to increased ectodomain shedding and that sMet levels could be a useful biomarker of tumorigenesis, tumor progression and overall tumor burden. In prior studies we found that increased Met shedding correlated with malignancy in several cell lines, and that urinary sMet levels were significantly elevated in metastatic prostate cancer patients relative to those with organ-confined cancer or no evidence of disease.

In an ongoing investigation of sMet as a diagnostic and/or prognostic biomarker of bladder cancer, the mean urinary sMet level among 150 patients with pathologically confirmed disease was significantly higher than that obtained from a group of 50 individuals with no evidence of disease, whether mean values were normalized to urine creatinine concentration or not (two-tailed Mann-Whitney t-test p-value &lt;0.001). Patients who underwent radical cystecomy had greater mean urinary sMet levels than patients with pTa and pT1 tumors, consistent with the likelihood that they had more advanced local disease. Our results so far confirm that sMet can be measured in human urine samples with a large dynamic range and sub-picomolar sensitivity, and reveal that urinary sMet may provide a reliable and practical indicator of malignant potential and overall tumor burden in individuals with bladder cancer. Continued sample collection and correlative analysis of sMet values and clinical data will help determine whether urinary sMet concentration will be a sensitive and reliable indicator of bladder cancer occurrence, tumor grade, stage and progression.

We have also measured plasma sMet levels in patients participating in a phase II clinical trial of Foretinib (formerly GSK1363089/XL880), a small molecule multikinase inhibitor targeting Met and vascular endothelial cell growth factor-2 (VEGFR-2) Axl and Ron, designed to evaluate the safety and efficacy of 2 dosing schedules (continuous daily dosing and intermittent 5 days on/9 days off dosing) of foretinib as a single therapeutic agent in patients with metastatic gastric carcinoma (GC). Plasma sMet concentrations, as well as plasma VEGF-A, HGF and soluble VEGFR-2 (sVEGFR-2) levels were measured before and during treatment with foretinib to measure potential pharmacodynamic (PD) effects and/or the modulation by foretinib of Met and VEGFR-2 pathways. Marker changes from baseline were analyzed at days 5, 15, 29 and 47 using analysis of variance and their relationships with plasma concentrations of foretinib (PK) and clinical outcome (sum of longest diameter [SLD] of tumor as a surrogate for tumor shrinkage, progression-free survival [PFS], and RECIST) were also examined. In GC patients on the intermittent dosing schedule, plasma sMet and VEGF-A concentrations tended to increase during the treatment periods compared with the drug holidays, suggestive of a direct short-term drug effect on sMet and VEGF-A levels. Although mean tumor burden did not change significantly from baseline to week 8, plasma levels of sMet and VEGF-A correlated positively with the change in SLD over this period, suggesting that the increases of sMet and VEGF-A may be reflective of increased GC tumor burden.

Citation Format: Fabiola Cecchi, Deborah Pajalunga, Brian McNeil, Daniel Rabe, Andrew Fowler, Yuan Liu, C. Robert Gagnon, Howard Kallender, Manish A. Shah, Robert Getzenberg, Mark Schoenberg, Anne-Marie Martin, Ramaprasad Srinivasan, W. Marston Linehan, R Andrew Byrd, Donald P. Bottaro. Oncogenic signal transduction via the hepatocyte growth factor/Met receptor kinase pathway [abstract]. In: Proceedings of the AACR 101st Annual Meeting 2010; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr SY23-03