The Precision of Hepatic Arterial Infusion Scintigraphy as a Quantitative Biomarker of Tumor Microvasculature

OBJECTIVE

Optimal clinical development of new cancer therapies targeting tumor vasculature requires new target-specific response assays. This clinical study examined the test-retest repeatability of SPECT as an in vivo assay of angiogenic hepatic tumor microvasculature using an intraarterial infusion of 99mTc-macroaggregated albumin (MAA) delivered via a hepatic artery infusion (HAI) pump.

MATERIALS AND METHODS

Patients with primary or secondary cancerous liver tumors with HAI pump-catheter implants placed for HAI chemotherapy underwent hepatic SPECT after separate arterial infusions of 37 and 185 MBq of 99mTc-MAA via an HAI pump. Quantitative measures of hepatic tumor MAA uptake were obtained from paired test-retest SPECT datasets. Repeatability was defined by quotients of paired measurands with 95% CIs and coefficients of repeatability (CRs).

RESULTS

Test-retest HAI pump SPECT yielded highly repeatable measurements in quantitative indexes of tumor microvasculature. Variability in repeat test-retest measurements was small relative to the range of observed measurements between different tumors. The total hepatic tumor microvascular MAA accumulation (percentage injected dose) proved most repeatable, with test-retest value quotients near unity (quotients: median, 1.10 ± 0.09 [SD]; range, 1.03-1.32; 95% CI, 1.07-1.19) and 1.6% CR. Tumor MAA uptake values ranged from 5% to 18% injected dose.

CONCLUSION

This article describes the precision of HAI SPECT as a quantitative biomarker of tumor microvasculature under conditions of repeatability. The results support clinical testing of HAI SPECT as a radiologic response biomarker for angiotropic tumor therapy.

Novel mouse models of hepatic artery infusion

BACKGROUND

The liver has unique anatomy in that most blood flow to normal hepatocytes is derived from the portal venous system, whereas liver tumors obtain their nutrient blood supply exclusively from the hepatic artery. The focused arterial delivery of anticancer agents to liver tumors has been performed for decades; however, preclinical models to standardize drug regimens and examine novel agents have been lacking. The purpose of this study was to establish preclinical hepatic artery infusion (HAI) models in a mouse and to evaluate the safety and delivery capability of the models.

MATERIAL AND METHODS

C57BL/6 and BALB/c mice were used to develop models of HAI via the hepatic artery (HA), superior pancreaticoduodenal artery (SPDA), or lienogastric artery (LGA). Success rates, distribution of perfusion, and associated morbidity and mortality were analyzed between groups.

RESULTS

All three models were feasible and reproducible in mice, and there was no statistical difference on body weight change between models. The HA model had a 13.3% mortality from acute liver failure, and the SPDA model demonstrated duodenal and pancreatic toxicity. SPDA and LGA routes had the highest success rates (96.7% and 91.4%, respectively) with low mortality, better drug delivery, and preserved physiologic liver function compared with the HA model.

CONCLUSIONS

The optimal route of HAI was mouse breed specific; SPDA access in BALB/c mice, and the LGA access in C57BL/6 mice. The described techniques serve as a reproducible platform for the identification and characterization of therapeutics for diverse metastatic liver tumors.

Tumour growth of colorectal rat liver metastases is inhibited by hepatic arterial infusion of the mTOR-inhibitor temsirolimus after portal branch ligation

Portal branch ligation (PBL) can be performed before major hepatic resection of colorectal liver metastases (mCRC) to increase the remnant liver mass. However, PBL may also stimulate mCRC growth through hepatic arterial hyperperfusion and growth factor release. Herein, we studied whether hepatic arterial infusion (HAI) of the mTOR-inhibitor temsirolimus (Tem) is capable of inhibiting the growth of colorectal liver metastases after PBL. WAG/Rij rats were randomized to four groups (n=6 each) and underwent subcapsular implantation of 5×10(5) CC531 cells into the left liver lobe. The animals of two groups underwent simultaneous PBL of the tumour bearing liver lobe. Ten days later animals underwent a HAI either of temsirolimus (Tem and PBL Tem) or saline solution (Sham and PBL Sham). Tumour size was analyzed at days 10 and 13 using three-dimensional ultrasound. In Sham controls tumour volume increased by 43%. After PBL Sham tumour volume increased by 52%. In contrast, in animals undergoing HAI of temsirolimus the tumour growth was not only completely inhibited, but tumour volume was found decreased, irrespective of PBL. After HAI of temsirolimus immunohistochemistry revealed an increased cleaved caspase-3 activity, indicating stimulation of apoptotic cell death. In parallel temsirolimus treatment was associated with a significant reduction of PECAM-1 positive cells within the tumour tissue, implying a reduced tumour vascularisation. HAI of temsirolimus is capable of inhibiting the growth of CC531 colorectal rat liver metastases also after PBL.

Phase I trial of hepatic arterial infusion (HAI) of floxuridine with modified oxaliplatin, 5-fluorouracil and leucovorin (m-FOLFOX6) in Chinese patients with unresectable liver metastases from colorectal cancer

PURPOSE

To determine the maximum tolerated dose (MTD) and preliminary efficacy of concurrent hepatic arterial infusion (HAI) of floxuridine (FUDR) and systemic modified oxaliplatin, 5-fluorouracil and leucovorin (m-FOLFOX6) in Chinese patients with unresectable hepatic metastases from colorectal cancer.

PATIENTS AND METHODS

Thirty-five patients with unresectable liver metastases with or without extrahepatic disease were treated with concurrent HAI and systemic m-FOLFOX6. HAI FUDR was delivered in a 14-day infusion with escalating dose levels, and each cycle was repeated every 4 weeks.

RESULTS

The MTD for FUDR was 0.12 mg/kg/day when combined with systemic m-FOLFOX6. The dose-limited toxicities were neutropenia (8.6 %), alanine aminotransferase/aspartate aminotransferase elevation (5.7 %) and diarrhea (11.4 %). The overall response rate was 68.6 % for hepatic metastases and 14.3 % for extrahepatic metastases. The median progression-free survival and overall survival were 8.23 and 25 months, respectively.

CONCLUSION

The recommended dose of FUDR was 0.12 mg/kg/day when combined with systemic m-FOLFOX6. This combination achieved a high response rate in hepatic disease and a high control rate in extrahepatic disease. Further study is needed to assess the potential additional value of HAI therapy in converting patients with hepatic metastases to candidates for resection.

Unresectable colorectal liver metastases: the safety and efficacy of conversion therapy using hepatic arterial infusion immunochemotherapy with 5-fluorouracil and polyethylene glycol-interferon α-2a

BACKGROUND

Hepatic arterial infusion (HAI) or systemic chemotherapy has been used to treat unresectable colorectal liver metastases. The prognosis of the disease in recent years has been improved because chemotherapy is performed before hepatectomy to reduce tumor size (conversion therapy). The purpose of this study was to investigate the safety and efficacy of conversion therapy following HAI immunochemotherapy.

METHODS

Hepatic arterial infusion of 5-fluorouracil (5-FU)/polyethylene glycol (PEG)-IFNα-2a was performed in 21 patients. The primary endpoint was the safety of HAI and hepatectomy. The secondary endpoints were response rate, rate of conversion to hepatectomy, survival rate, and prognostic factors.

RESULTS

With regard to side effects, drugs were discontinued temporarily in one patient because of a decrease in white blood cell count; however, other patients continued chemotherapy. The response rate with HAI was 61.9 %, and the conversion rate was 38.1 %. Hepatectomy was completed successfully without mortality. Median progression-free survival (PFS) was 11.5 months (with and without conversion, 16.7 and 4.8 months, respectively; p = 0.021). Median overall survival was 34.6 months (with and without conversion, 48.4 and 26.6 months, respectively; p = 0.003). Prognosis was poor when the number of metastatic tumors was ≥10 [PFS: hazard ratio (HR) 32.21, p = 0.003; overall survival (OS): HR 9.13, p = 0.07], but prognosis improved after hepatectomy (OS: HR 0.08, p = 0.09).

CONCLUSIONS

Hepatic arterial infusion immunochemotherapy with 5-FU/PEG-IFNα-2a was performed safely without major side effects. Prognosis is expected to improve after successful conversion to hepatectomy.

Surgery for colorectal liver metastases

Half of all patients with colorectal cancer develop metastatic disease. The liver is the principal site for metastases, and surgical resection is the only modality that offers the potential for long-term cure. Appropriate patient selection for surgery and improvements in perioperative care have resulted in low morbidity and mortality rates, resulting in this being the therapy of choice for suitable patients. Modern management of colorectal liver metastases is multimodal incorporating open and laparoscopic surgery, ablative therapies such as radiofrequency ablation or microwave ablation and (neo)adjuvant chemotherapy. The majority of patients with hepatic metastases should be considered for resectional surgery, if all disease can be resected, as this offers the only opportunity for prolonged survival.

Hepatic arterial infusion but not systemic application of cetuximab in combination with oxaliplatin significantly reduces growth of CC531 colorectal rat liver metastases

PURPOSE

Systemic chemotherapy still represents the gold standard in the treatment of irresectable colorectal liver metastases. Modern anticancer agents like the monoclonal antibody cetuximab have improved the outcome of patients in clinical studies. As hepatic arterial infusion (HAI) is capable to potentially increase the anticancer effect of cytostatics, we herein studied whether HAI of cetuximab (CE) as a single agent or in combination with oxaliplatin (OX) exerts increased anticancer effects compared to the systemic application (SYS) of the drugs.

METHODS

WAG/Rij rats were randomized to eight groups and underwent 10 days after subcapsular hepatic tumor implantation either HAI or SYS of CE, OX, or the combination of both agents (CE + OX). Saline-treated animals served as controls. Tumor volume was measured at days 10 and 13 using three-dimensional ultrasound. On day 13, liver and tumor tissue was sampled for histological and immunohistochemical analysis.

RESULTS

In controls, the tumor volume significantly increased from day 10 to 13. Application of OX alone via HAI or SYS did not inhibit tumor growth compared to controls. SYS of CE or CE + OX did also not reduce tumor growth. In contrast, HAI of CE and CE + OX significantly inhibited tumor growth. HAI of CE significantly reduced tumor vascularization as measured by the number of platelet endothelial cell adhesion molecule-1-positive cells and significantly increased the number of apoptotic tumor cells as measured by the cellular caspase-3 expression.

CONCLUSION

HAI of CE and CE + OX reduces tumor growth of colorectal rat liver metastases involving the inhibition of angiogenesis and induction of tumor cell apoptosis.

Liver-directed chemotherapy of cetuximab and bevacizumab in combination with oxaliplatin is more effective to inhibit tumor growth of CC531 colorectal rat liver metastases than systemic chemotherapy

Colorectal carcinoma is, through to its high rate of liver metastasis (mCRC), the second most cause of cancer death worldwide. Tumor resection represents the only potential cure. In cases of unresectable disease systemic chemotherapy (sCHT) remains the therapy of choice. Modern sCHT regimens including biological agents can induce tumor response that leads to curative surgery of initially unresectable mCRC. However, liver-directed therapy via hepatic arterial infusion (HAI) may produce higher response rates than sCHT. Herein we studied whether a HAI of cetuximab (CE) plus bevacizumab (BE) with or without oxaliplatin (OX) can inhibit tumor growth in a rat model. WAG/Rij rats underwent subcapsular hepatic tumor implantation. After 10 days animals received either HAI or sCHT of CE plus BE, OX or all three drugs. Saline-treated animals served as controls. Tumor growth was estimated at day 10 and 13. On day 13 liver and tumor tissue was studied histologically and immunohistochemically. In controls the tumors grew about 50 %. OX alone was not capable of inhibiting tumor growth. In contrast, CE plus BE given as HAI significantly reduced tumor growth compared to sCHT (p < 0.05). HAI of CE plus BE combined with OX yielded an even more pronounced inhibition of tumor growth. Immunohistochemistry revealed a decreased tumor cell proliferation and tumor vascularization. The present study demonstrates that HAI of CE plus BE is effective to inhibit tumor growth. This effect is even more pronounced in combination with OX. Systemic application of these agents cannot achieve comparable effects.

Advancing the scope of nursing practice: hepatic arterial catheter removal

A delay in hepatic artery infusion catheter removal may prolong patient discomfort and lead to additional complications. As a result, this article evaluated the effectiveness of shifting the responsibility of catheter removal from advanced practice or medical staff to nurses. Overall, patients were satisfied, felt comfortable, and experienced minimal pain irrespective of whether their catheter was removed by a nurse, physician, or advanced practice staff. Nurses also were satisfied and felt they had enhanced their ability to provide quality patient care.

Curable metastatic colorectal cancer

In the United States and Europe, colorectal cancer (CRC) is the third most common malignancy and the second leading cause of cancer-related death for men and women. In the course of their disease, many patients will present with metastasis, with the liver and lung being the most common locations. Untreated metastatic disease carries a poor prognosis. However, cure is still possible for selected patients with stage IV CRC. Surgical resection provides the best chance for cure, and chemotherapy can be a valuable adjunct when given in a (neo-)adjuvant fashion or as conversion therapy to downsize initially unresectable tumors. For unresectable metastases, alternative treatment options include radiofrequency ablation and hepatic artery infusion. Additional local therapies are being explored, including chemoembolization, radioembolization, and stereotactic body radiation therapy. Prospective randomized trials are needed to further clarify the roles of these novel treatment options in the clinician's repertoire for metastatic CRC.

Phase I clinical trial of hepatic arterial infusion of paclitaxel in patients with advanced cancer and dominant liver involvement

PURPOSE

The survival of patients with liver metastases from solid tumors is poor. We conducted a phase I study of hepatic arterial infusion (HAI) paclitaxel in patients with advanced cancer and predominant liver involvement.

METHODS

Patients were treated with HAI paclitaxel 150-275 mg/m(2) (and 15,000 IU heparin intraarterially) every 28 days. A "3 + 3" study design was used.

RESULTS

Twenty-six patients were treated (median age, 59 years). Diagnoses were colorectal cancer (n = 10), breast cancer (n = 7), and other (n = 9). The median number of prior therapies was four (range, 0-10). The maximum tolerated dose (MTD) was HAI paclitaxel 225 mg/m(2). Dose-limiting toxicities (DLTs) included Grade 3 neuropathy (1 of 5 patients) at HAI paclitaxel 275 mg/m(2) and Grade 4 thrombocytopenia and neutropenia, and Grade 3 mucositis (1 of 4 patients) at 250 mg/m(2). None of the eight patients treated with HAI paclitaxel 225 mg/m(2) experienced a DLT. The most common toxicities were nausea and peripheral neuropathy. Of 22 patients evaluable for response, 3 (13.6%) patients had SD for ≥4 months (colorectal cancer, n = 1; thyroid cancer, n = 1; and hepatocellular carcinoma, n = 1; duration of response was 4 months, 7.1 months, and 22.2+ months, respectively).

CONCLUSION

The MTD of HAI paclitaxel was 225 mg/m(2). This regimen was well tolerated and had antitumor activity in selected patients.

A phase 1 study of hepatic arterial infusion of oxaliplatin in combination with systemic 5-fluorouracil, leucovorin, and bevacizumab in patients with advanced solid tumors metastatic to the liver

BACKGROUND

Liver metastases in patients with cancer are associated with poor survival. The authors of this report conducted a phase 1 study of hepatic arterial infusion (HAI) oxaliplatin combination therapy in patients with advanced cancer and liver metastases.

METHODS

Treatment consisted of escalating doses of HAI oxaliplatin 60 mg/m(2) to 175 mg/m(2) and intra-arterial heparin 3000 IU (Day 1); leucovorin 200 mg/m(2) intravenously (iv) and 5-fluorouracil 300 mg/m(2) bolus plus 600 mg/m(2) iv (Days 1 and 2); and bevacizumab 10 mg/kg iv (Day 3). A conventional "3 + 3" design was used.

RESULTS

Fifty-seven patients were treated, including 30 women and 27 men. The median age was 57 years, and the patients had received a median of 3 prior therapies (range, 1-7 prior therapies). The most common cancer was colorectal (n = 29). Overall, 204 cycles were administered (median per patient, 2 cycles; range, 1-17 cycles). The maximum tolerated dose (MTD) of HAI oxaliplatin was 140 mg/m(2). Dose-limiting toxicities were grade 4 thrombocytopenia (n = 1) and grade 4 hypokalemia (n = 1) at 150 mg/m(2) (n = 5). Thirty-three patients (58%) had no toxicity greater than grade 1. The most common toxicities were thrombocytopenia (n = 19), fatigue (n = 15), nausea/vomiting (n = 6), constipation (n = 6), and diarrhea (n = 4). Of 55 patients who were evaluable for response (according to Response Evaluation Criteria in Solid Tumors), 4 patients (7%) had a partial response (PR), and 32 patients (58%) had stable disease (SD), including 15 patients (48%) who had SD for >/=4 months. Of 28 patients with colorectal cancer, 3 patients (11%) had a PR, and 9 patients (32%) had SD for >/=4 months.

CONCLUSIONS

HAI oxaliplatin combined with systemic 5-fluorouracil, leucovorin, and bevacizumab had antitumor activity in patients with advanced cancer and liver metastases, and the current results indicated that this combination warrants further study. Cancer 2010. (c) 2010 American Cancer Society.

The role of chemotherapy in managing patients with resectable liver metastases

Colorectal cancer metastatic to the liver is a common oncologic problem, and carefully selected patients can be successfully treated with surgical resection of liver metastases. Perioperative chemotherapy has been shown to increase progression-free survival in patients with resectable liver metastases and can currently be considered a standard therapy for eligible patients. Preoperative chemotherapy can downstage unresectable liver metastases and allow a complete resection. More aggressive chemotherapy as well has the incorporation of targeted agents such as cetuximab and bevacizumab into modern chemotherapy regimens has resulted in higher response rates, which may translate into improved survival. Preoperative chemotherapy can increase postoperative complications after hepatic resection, and the decision to use such therapy should be made in a multidisciplinary setting.

Management of an incidental liver mass

The increased use of sensitive imaging modalities has led to increased identification of the incidental liver mass (ILM). A combination of careful consideration of patient factors and imaging characteristics of the ILM enables clinicians to recommend a safe and efficient course of action. Using an algorithmic approach, this article includes pertinent clinical factors and the specific radiologic criteria of ILMs and discusses the indications for potential procedures. It is the aim of this article to assist with the development of an individualized strategy for each patient with an ILM.

Multi-institutional study of risk factors of liver metastasis from colorectal cancer: correlation with CD10 expression

BACKGROUND

The risk factors for liver metastasis from colorectal cancer are still unclear. We therefore evaluated the relationships between various clinicopathological factors, including CD10 expression, liver metastasis, and survival, in patients with colorectal cancer.

METHODS

Clinicopathological data for 1,025 patients with stage II or III colorectal cancer who underwent curative surgery in four participating hospitals were collected and evaluated. Three pathologists examined focal dedifferentiation, venous invasion, and CD10 expression without knowledge of the clinical outcome.

RESULTS

Univariate analysis showed that pathological T (pT), pathological N (pN), venous invasion, focal dedifferentiation, and CD10 expression were significantly associated with liver metastasis. Multivariate analysis selected pT, pN, and CD10 expression as significant risk factors for liver metastasis. pT, pN and CD10 were also shown by univariate and multivariate analyses to be significantly associated with disease-free survival. The incidence of liver metastasis was 3% in pN0 patients with CD10-negative or pT2 or pT3 tumors and 28% in pN2 patients with CD10-positive or pT4 tumors.

CONCLUSIONS

CD10 expression is a significant risk factor for liver metastasis in patients with colorectal cancer and is correlated with prognosis. Patients with a high risk of liver metastasis can be selected on the basis of pT, pN, and CD10 expression.

Phase I study of hepatic arterial infusion of oxaliplatin in advanced hepatocellular cancer: a brown university oncology group study. Am J Clin Oncol. 2010;33:43-46. [PMID: 19687731 DOI: 10.1097/coc.0b013e31819d8668]

PURPOSE

We performed a phase I study to evaluate the feasibility and determine the maximally tolerated dose of hepatic arterial infusion (HAI) of oxaliplatin in advanced hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Patients with unresectable or recurrent HCC received HAI-oxaliplatin over 2 hours at dose escalation levels of 90, 110, 130, and 150 mg/m given every 3 weeks. The therapy was continued until disease progression or excessive toxicity not amenable to appropriate modifications. Restaging was performed after every 2 cycles.

RESULTS

A total of 23 patients were enrolled, with 17 patients evaluable for toxicity assessment. The median age was 63 years (range: 47-84 years), with 22 men and 1 woman. Stage distribution was as follows: stage II, 3 patients; stage III, 12 patients; and stage IV, 8 patients. A total of 53 cycles (range: 1-3) of HAI-oxaliplatin were delivered. The conventional grade 3/4 hematologic and gastrointestinal toxicities were infrequent. Among 17 evaluable patients receiving >2 cycles, 3 patients had partial responses and 8 had stable disease. A greater than 50% reduction in alphafetoprotein was seen in the 3 patients with partial responses and 3 patients with stable disease.

CONCLUSIONS

HAI-oxaliplatin is a feasible, well tolerated, and demonstrated activity in this advanced HCC cohort. HAI-oxaliplatin 150 mg/m every 3 weeks was determined as the dose for further evaluation in phase II trials.

Phase I clinical trial of hepatic arterial infusion of cisplatin in combination with intravenous liposomal doxorubicin in patients with advanced cancer and dominant liver involvement

PURPOSE

We conducted a phase I study of hepatic arterial infusion (HAI) cisplatin and systemic chemotherapy in patients with advanced cancer and dominant liver involvement.

METHODS

Patients were treated with HAI cisplatin 100-125 mg/m(2) (and 3,000 IU heparin) intraarterially and liposomal doxorubicin (doxil) 20-35 mg/m(2) IV (day 1) every 28 days. A "3 + 3" study design was used.

RESULTS

Thirty patients were treated (median age, 56 years). Diagnoses were breast cancer (n = 11), colorectal cancer (n = 8), ocular melanoma (n = 4), and other (n = 7). The median number of prior therapies was 5. The maximum tolerated dose (MTD) was at the 100/35 mg/m(2) level. Dose-limiting toxicities were Grade 4 neutropenia (2 of 4 patients), and Grade 4 thrombocytopenia (n = 1) at the cisplatin 125 mg/m(2) and systemic doxil 35 mg/m(2) dose level. The most common toxicities were nausea/vomiting and fatigue. Of 24 patients evaluable for response, 4 (17%) had a partial response (PR) and 7 (29%) had stable disease (SD) for ≥4 months. Of the 11 patients with breast cancer, 3 (27%) had a PR and 5 (45%) had SD for ≥4 months. Of 4 patients with ocular melanoma, 1 had a PR and 1 SD for 4 months. One patient with hepatocellular carcinoma had SD for 4 months. Of 12 evaluable patients treated at the MTD, 2 (17%) had a PR and 5 (42%) had SD.

CONCLUSION

The MTD was HAI cisplatin 100 mg/m(2) and systemic doxil 35 mg/m(2). This regimen demonstrated antitumor activity, especially in breast cancer.

New insights into the biotransformation and pharmacokinetics of oxaliplatin

Oxaliplatin is used primarily in the treatment of metastatic colorectal cancer. In this minireview, we discuss potentially important biotransformation pathways in light of its short elimination half-life in vivo. We also highlight new information achieved using a selective analytical technique to measure intact oxaliplatin in pharmacokinetic studies (comprising intravenous, intraperitoneal, and intrahepatic administration) and compare to results obtained by measurements of total platinum. The use of selective analytical techniques is strongly recommended giving kinetic parameters of the parent compound and not only to a complex mixture of platinum containing endogenous compounds.

Development of arterial blood supply in experimental liver metastases

In this study, we present a mechanism for the development of arterial blood supply in experimental liver metastases. To analyze the arterialization process of experimental liver metastases, we elucidated a few key questions regarding the blood supply of hepatic lobules in mice. The microvasculature of the mouse liver is characterized by numerous arterioportal anastomoses and arterial terminations at the base of the lobules. These terminations supply one hepatic microcirculatory subunit per lobule, which we call an arterial hepatic microcirculatory subunit (aHMS). The process of arterialization can be divided into the following steps: 1) distortion of the aHMS by metastasis; 2) initial fusion of the sinusoids of the aHMS at the tumor parenchyma interface; 3) fusion of the sinusoids located at the base of the aHMSs, which leads to the disruption of the vascular sphincter (burst pipe); 4) incorporation of the dilated artery and the fused sinusoids into the tumor; and 5) further development of the tumor vasculature (arterial tree) by proliferation, remodeling, and continuous incorporation of fused sinusoids at the tumor-parenchyma interface. This process leads to the inevitable arterialization of liver metastases above the 2000- to 2500-mum size, regardless of the origin and growth pattern of the tumor.

Linkage of pluripotent stem cell-associated transcripts to regulatory gene networks

Knowledge of the transcriptional circuitry responsible for pluripotentiality and self-renewal in embryonic stem cells is tantamount to understanding early mammalian development and a prerequisite to determining their therapeutic potential. Various techniques have employed genomics to identify transcripts that were abundant in stem cells, in an attempt to define the molecular basis of 'stemness'. In this study, we have extended traditional genomic analyses to identify cis-elements that might be implicated in the control of embryonic stem cell-restricted gene promoters. The strategy relied on the generation of a problem-specific list from serial analysis of gene expression profiles and subsequent promoter analyses to identify frameworks of multiple cis-elements conserved in space and orientation among genes from the problem-specific list. Subsequent experimental data suggest that 2 novel transcription factors, B-Myb and Maz, predicted from these models, are implicated either in the maintenance of the undifferentiated stem cell state or in early steps of differentiation.