Abstract 237: Evaluation of cell membrane lipid-extracted nanoliposomes (CLENs) as a potential drug platform for targeting multiple myeloma

Background: Multiple myeloma (MM) is a plasma cell malignancy that primarily affects the elderly. MM is the second most common hematologic cancer with approximately 25,000-30,000 new cases diagnosed annually in the United States. A challenge associated with MM therapy is unwanted drug uptake by normal healthy cells. Nanoparticles provide a promising outlook to mitigate these issues, offering more selective drug uptake, while minimizing toxicity associated with treatment. The objective of this study was to develop, optimize and evaluate physicochemical and In vitro properties of MM-CLENs in comparison to conventional liposomes and relevant cell controls.

Methods: RPMI-8226 MM cell line was selected cellular model for MM disease. RPMI-8226 cells were cultured and expanded In vitro for cellular extraction purposes. Lipid extraction (LE) procedures were performed to generate the RPMI-8226 LE ingredient. Other lipid ingredients used in preparation of RPMI-8226 CLENs included DOPC, cholesterol, and DPPE-Rhodamine (fluorescence indicator). Phase I included physicochemical characterization and cellular uptake studies of CLENs preparations with varying concentration of RPMI-8226-LE (0 to 40 mol%) content. Phase II began with the optimized concentration of LE determined in Phase I, along with varying concentrations of cholesterol (0 to 40 mol %) content for the nano-targeting studies in vitro. The control cell lines represent other hematological diseases, K-562-GFP (chronic myeloid leukemia), CCRF-CEM (acute lymphoblastic leukemia), and U937 (lymphoma).

Results: Phase I and II physicochemical characterization and In vitro studies, revealed that the optimized preparation of RPMI-8226-CLENs consisted of 5% LE, and 5% cholesterol content. Optimal preparation consisted of DOPC: Cholesterol: LE (90:5:5) with an average values for particle size and zeta potential of 178±38 nm (n=4), and -14±4 mV (n=4), respectively. The inclusion of LE in conventional DOPC:cholesterol liposomes resulted in significantly improved uptake of the CLENs by RPMI-8226 cells in vitro (P< 0.001). However, preliminary selectivity studies suggest no significant difference in the uptake of RPMI-8226-CLENs by RPMI-8226 when compared to control cells (K-562-GFP, CCRF-CEM and U937).

Conclusion: Studies involving RPMI-8226 CLENs are currently underway. Such studies include target selectivity, and influence of additional components of CLENs as a function of the microenvironment.

Citation Format: Christina T. Tran, Eden Park, Pedro L. Rodriguez-Flores, Robert B. Campbell. Evaluation of cell membrane lipid-extracted nanoliposomes (CLENs) as a potential drug platform for targeting multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 237.

Therapeutic Management of Lymphoma: Conventional Strategies and Overcoming Treatment Barriers with Nanotherapeutics

Abstract:

According to the American Cancer Society, the prevalence of lymphoma remains high in the United States with an estimated 90,390 new cases, and 21,680 deaths annually. Although current chemotherapeutic regimens approved by the FDA can effectively improve treatment outcomes, the prognosis remains poor with numerous complications. Current therapeutic strategies have faced multiple challenges limiting desired therapeutic effects. With the multitude of clinical barriers faced by conventional treatment strategies, researchers continue to explore the use of nanotherapeutics over more conventional treatment options. The engineered nanoparticles include starting materials from a number of biocompatible sources, and the final products can safely incorporate therapeutic agents, improve drug selectivity to tumor targets, and enhance efficacy profiles, all while reducing toxicity associated with the drug payload. These are tremendous potential advantages. This review summarizes the molecular basis of lymphoma, disease progression, and therapeutic challenges encountered during treatment. The discussions further highlight preclinical and clinical results at the different clinical stages, reviewing the different types of lymphoma, and summarizing how nanotherapeutics have addressed challenges confronting treatment.

Drug Targeting and Therapeutic Management of Chronic Myeloid Leukemia: Conventional and Nanotherapeutic Drug Options

Chronic myeloid leukemia (CML) is a blood cancer predominantly affecting older adult patients. According to the American Cancer Society, an estimated 8,860 people will be diagnosed with CML in 2022. Treatments for CML have evolved with a focus on CML phase severity or progression. Overall, there have been some breakthrough treatment options for a high percentage of patients with CML. This is largely due to the discovery of tyrosine kinase inhibitors (TKI); however, drug resistance continues to present a significant challenge for the management of CML disease.  The use of interferon (IFN), antimetabolites, and bone marrow transplants provide alternative treatment options, but also present with limitations including severe side effects, toxicity, and graft versus host disease. Nanomedicine has demonstrated benefits in terms of efficacy, often reducing or eliminating unwanted toxicities associated with the use of conventional drug agents. This review summarizes rational molecular targets of CML drugs and provides highlights of current FDA-approved agents for the treatment of CML. Additionally, this communication includes an overview of the limitations of conventional treatments and how nanomedicine has addressed challenges encountered during CML treatment. .

An Overview of Conventional Drugs and Nano Therapeutic Options for the Treatment and Management of Pediatric Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is a common form of pediatric cancer affecting the lymphoblast, a type of white blood cell found in the bone marrow. In this disease, the normal lymphoblast cells transform into leukemic cells and subsequently enter the bloodstream. Leukemic cells found in patients with ALL have shown differences in cholesterol uptake and utilization. Current treatment consists of chemotherapy, chimeric antigen receptor (CAR) therapy, and hematopoietic stem cell transplantation (HSCT). In addition, minimal residual disease (MRD) has become an effective tool in measuring treatment efficacy and the potential for relapse. Chemotherapy resistance remains a significant barrier in the treatment of ALL. Biomarkers such as an upregulated Akt signaling pathway and an overexpressed VLA-4 integrin-protein have been associated with drug resistance. Nanoparticles have been used to favorably alter the pharmacokinetic profile of conventional drug agents. These drug-delivery systems are designed to selectively deliver their drug payloads to desired targets. Therefore, nanoparticles offer advantages such as improved efficacy and reduced toxicity. This review highlights conventional treatment options, distinctive characteristics of pediatric ALL, therapeutic challenges encountered during therapy, and the key role that nanotherapeutics play in the treatment of ALL.

Drug Targeting and Conventional Treatment of Multiple Myeloma: Analysis of Target Specific Nanotherapies in Disease Models

Abstract:

Extensive studies have explored potential therapies against multiple myeloma (MM), whether in hospitals, universities, or in private institutional settings. Scientists continue to study the mechanism(s) underlying the disease as a basis for the development of more effective treatment options. There are many therapeutic agents and treatment regimens used for multiple myeloma. Unfortunately, no cure or definitive treatment options exist. The goal of treatment is to maintain the patient in remission for as long as possible. Therapeutic agents used in combination can effectively maintain patients in remission. While these therapies have increased patient survival, a significant number of patients relapse. The off-target toxicity and resistance exhibited by target cells remain a challenge for existing approaches. Ongoing efforts to understand the biology of the disease offer the greatest chance to improve therapeutic options. Nanoparticles (targeted drug delivery systems) offer new hope and directions for therapy. This review summarizes FDA approved agents for the treatment of MM, highlights the clinical barriers to treatment, including adverse side effects normally associated with the use of conventional agents, and describes how nanotherapeutics have overcome barriers to impede conventional treatments.

Evaporation and propagation of liquid drop streams at vacuum pressures: Experiments and modeling

Evaporation of streams of liquid droplets in environments at vacuum pressures below the vapor pressure has not been widely studied. Here, experiments and simulations are reported that quantify the change in droplet diameter when a steady stream of ≈100 μm diameter drops is injected into a chamber initially evacuated to <10^{-8}bar. In experiments, droplets fall through the center of a 0.8 m long liquid nitrogen cooled shroud, simulating infinity radiation and vapor mass flux boundary conditions. Experimentally measured changes in drop diameters vary from ≈0 to 6 μm when the initial vapor pressure is increased from 10^{-6} to 10^{-3} bar by heating the liquid. Measured diameter changes are predicted by a model based on the Hertz-Knudsen equation. One uncertainty in the calculation is the "sticking coefficient" β. Assuming a constant β for all conditions studied here, predicted diameter changes best match measurements with β≈0.3. This value falls within the range of β reported in the literature for organic liquids. Finally, at the higher vapor pressure conditions considered here, the drop stream disperses transverse to the main flow direction. This spread is attributed to forces imparted by an absolute pressure gradient produced by the evaporating stream.

Abstract 4666: An evaluation of breast cancer cellular membrane lipid-extracted nanoliposomes (CLENs) in relation to formulation design, stability, mechanism of cellular entry and cardioprotective function in vitro

One of the longstanding issues limiting the use of chemotherapeutic agents is the lack of tumor specificity, which leads to systemic toxicity. Therefore, various targeted nanocarriers have been developed to concentrate the cytotoxic drug agents at tumor regions to avoid uptake by normal healthy tissues. Previous studies from our laboratory have demonstrated that cell membrane lipid-extracted nanoliposomes (CLENs) are capable of selective targeting compared to nanoliposomes consisting of mainly conventional lipid materials. Also, CLENs were relatively nontoxic when employed at concentrations traditionally used to evaluate nanoparticles in vitro. However, parameters such as lipid composition, size, and surface charge all have a direct impact on liposomal cellular uptake. In this study, we prepared different CLENs different molar ratios of natural and cellular-derived lipids extracted directly from breast cancer cells (4T1), cholesterol, and DPPE-PEG-5000. The formulations were used to investigate the mechanisms of CLENs uptake and determine the underlying mechanisms regulating cellular entry. In the study, CLENs were used to evaluate cytotoxicity and cellular uptake for both target and off-target cell populations. CLENs containing cholesterol and DPPE-PEG-5000 (70/25/5) were able to retain doxorubicin in relevant therapeutic concentrations. CLEN formulations were able to exert selective cytotoxic drug effects against different target breast cancer cells in vitro. 4T1 CLENs containing cholesterol and DPPE-PEG-5000 (70/25/5) demonstrated greater binding to 4T1 (target) cells compared to CLENs prepared using 4T1 lipid extracts alone. The binding was not only temperature- and time-dependent, but also composition- and cell type-dependent. Off-target effect studies showed that 4T1 CLENs were taken up minimally by off-target cells (including normal breast fibroblasts and normal myocytes), compared to controls. Our studies collectively support the use of lipid extracts derived from target cells for selective drug targeting and enhanced cytotoxicity. Future studies will explore underlying mechanisms of cellular entry and cardioprotective function.

Citation Format: Hanan M. Alharbi, Robert B. Campbell. An evaluation of breast cancer cellular membrane lipid-extracted nanoliposomes (CLENs) in relation to formulation design, stability, mechanism of cellular entry and cardioprotective function in vitro [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4666.

Piloting Your Nanovehicle to Overcome Biological Barriers

Designing an effective nanoparticle for selective drug transport requires careful consideration of the complex biological barriers encountered in transit to the desired target. Here, we review several of these barriers, and provide possible methods for formulating liposomal nanoparticles to overcome them. The methods include the biotinylation of an antibody, and subsequent conjugation to a PEGylated cationic lipid nanoparticle. Additionally, the incorporation of drug, and other relevant characteristics of the nanoparticle are also discussed.

Abstract 5513: Employing a unique panel of breast cancer cellular lipids extracts in the development of a novel nanoliposome drug platform

Breast cancer is a major cause of cancer death in women worldwide. Breast cancer is a heterogeneous disease characterized by variant pathological features, disparate responses to therapeutics, and substantial differences in patient's long-term survival. The use of drug delivery systems such as liposomes can favorably alter the pharmacokinetic and biodistribution profile of commonly used drugs used to treat breast cancer disease.

An important feature of a drug delivery system is its ability to recognize and selectively target tumor cells with relatively high affinity when compared to healthy tissues. For this reason, the goal of this study was to develop a novel nanoliposome system that would target tumor cells to a significantly greater extent when compared to more conventional liposome systems. In this study, natural lipids extracted directly from breast cancer cells were used to prepare cellular lipid-extracted nanoliposomes (CLENs). The rationale is that an array of different lipids with a unique composition profile would represent a more relevant source of lipid material when compared to more traditional methods of liposome preparation. We therefore investigated whether the inclusion of extracted lipids derived from breast cancer cells would improve the selective uptake of liposomes by breast cancer cells, and related formulation features. To achieve these goals, three breast cancer cell lines were used (4T1, BT-20, and SK-BR-3), a normal breast fibroblast (CRL-2089), and an ovarian cancer cell line (SK-OV-3- used as a negative control).

The size of CLENs fell within the size range of 120- 203 nm and possessed a negatively-charged liposome surface charge potential (ranging between -10.97 and -20.97 mV). The nanoliposomes were also non-toxic to cells within the concentration range evaluated (up to 1μmol). Furthermore, without exception, the cellular uptake of CLENs was greatest when the extracted material used to prepare CLENs was the same as the target cell from which the lipids were extracted. In addition, when the breast cancer cell lines (4T1, SK-BR-3 and BT-20) were used to prepare CLENs, SK-OV-3 and CRL-2089 cell lines took up CLENs to a lesser extent, suggesting a more selective and differential cellular uptake.

In conclusion, the novel nanoliposome platform represents a promising drug delivery alternative to more conventional nano drug delivery systems. Additional formulation studies are currently underway.

Citation Format: Hanan M. Alharbi, Robert B. Campbell. Employing a unique panel of breast cancer cellular lipids extracts in the development of a novel nanoliposome drug platform. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5513. doi:10.1158/1538-7445.AM2015-5513

Abstract 4554: An evaluation of the role of Mucin in drug resistant ovarian cancer

MUC1 is a transmembrane glycoprotein that is overexpressed in epithelial ovarian cancer. Due to extensive O-glycosylation, mucins form a physical barrier that limits the intracellular accumulation and cytotoxic effect of chemotherapeutic drugs. Our investigation represents a key step in determining if drug resistance in ovarian cancer develops due to altered MUC1 expression and glycosylation. Immunoblotting and ELISA techniques were utilized to characterize the extent of membrane-bound and shed MUC1 expression in drug-resistant and drug-sensitive ovarian cancer cells. An (anti-MUC1) antibody-based in vitro model was employed to determine if the inhibition of O-glycosylation enhanced functional access of small molecule drugs using FACS and fluorescence microscopic analyses. Expression of MUC1 was detected in both the drug resistant ovarian cancer cell line SK-OV-3 (MDR) and the parent cell line SK-OV-3 (WT), with the highest levels observed in the drug resistant sub-clone. The greatest improvement in functional anti-MUC1 antibody access following inhibition of O-glycosylation was observed in the drug-resistant ovarian cancer cells. Our results provide evidence to support drug resistance in ovarian cancer due in part to a mucin barrier mesh. The inhibition of mucin O-glycosylation may be a viable strategy to improve drug delivery and efficacy of small molecule delivery to ovarian carcinomas.

Citation Format: Steven M. Richards, Robert B. Campbell. An evaluation of the role of Mucin in drug resistant ovarian cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4554. doi:10.1158/1538-7445.AM2015-4554

The effect of inbreeding constraints and offspring distribution on time to the most recent common ancestor

The expected time to the most recent common ancestor (MRCA) of two alleles in a diploid individual is 4N+2 under random mating with a Poisson progeny distribution, but 8N-2 under maximum avoidance of inbreeding, which entails two progeny per mating pair. (N is the number of mating pairs, hence 2N is the number of individuals, hence 4N is the number of alleles.) The interrelationship of inbreeding constraints and offspring distribution is investigated by varying the level of sib mating: prohibiting sib mating increases the time to MRCA by four generations and decreases the variance of the offspring distribution by 2/N. With two progeny per mating pair, the expected time to the MRCA is 8N-2 under both random mating and sib mating prohibited, as well as under maximum avoidance of inbreeding, but this result does not hold for all mating structures with two progeny per mating pair.

Abstract 4473: Development of ceramide liposomes for tumor interstitial and vascular drug targeting

Background: Interstitial and vascular targeting with cytotoxic agents has proven to be an effective approach for cancer therapy (1). Ceramide, a sphingolipid, plays an important role in apoptosis, regulation of differentiation, growth suppression, and in cell senescence (2). Liposomes containing ceramide exert an anti-proliferative effect against the growth of tumor cells in vitro (3). In this study, we attempted to apply a rational approach to the development of ceramide liposomes for tumor targeting.

Methods: We first determined the relative amounts of ceramide produced by cells normally found in the tumor interstitial matrix (ZR-75-1- human breast cancer cells), and by those lining tumor endothelia (HMEC-1 -human microvascular endothelial cells). For this experiment we measured sphingomyelinase activity. We next determined the cytotoxic effects of various liposome systems containing 0 to 20% ceramide (C6:1) content. The optimal ceramide content was determined from this study, and 2-methoxyestradiol (2-ME) was loaded in the optimal ceramide liposome preparation type. We next evaluated cytotoxic effects of the drug-loaded liposomes compared to ceramide liposomes alone.

Results: ZR-75-1 cells showed a higher level of sphingomyelinase activity (4.4 fold) as compared to that of HMEC-1. The 20% ceramide formulation demonstrated the most significant anti-proliferative effect, regardless of the cell line. The cytotoxic drug effects were favorably influenced by the ceramide content. Finally, preliminary studies suggest that the overall effectiveness of ceramide liposomes against the growth of proliferating tumor cells correlated with the sphingomyelinase activity expressed by the target cells.

Conclusion: Future studies will determine whether sphingomyelinase activity can be used to determine the population of cells (i.e., interstitial vs vascular) most likely to benefit from ceramide (cytotoxic) drug-loaded liposomes as a therapeutic approach.

Citation Format: Shaohua Cheng, William Crall, Bryan Nguyen, Charles Dang, Musaed Alkholief, Robert B. Campbell. Development of ceramide liposomes for tumor interstitial and vascular drug targeting. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4473. doi:10.1158/1538-7445.AM2014-4473

Monitoring of magnetic targeting to tumor vasculature through MRI and biodistribution

AIMS

The development of noninvasive imaging techniques for the assessment of cancer treatment is rapidly becoming highly important. The aim of the present study is to show that magnetic cationic liposomes (MCLs), incorporating superparamagnetic iron oxide nanoparticles (SPIONs), are a versatile theranostic nanoplatform for enhanced drug delivery and monitoring of cancer treatment.

MATERIALS & METHODS

MCLs (with incorporated high SPION cargo) were administered to a severe combined immunodeficiency mouse with metastatic (B16-F10) melanoma grown in the right flank. Pre- and post-injection magnetic resonance (MR) images were used to assess response to magnetic targeting effects. Biodistribution studies were conducted by ¹¹¹In-labeled MCLs and the amount of radioactivity recovered was used to confirm the effect of targeting for intratumoral administrations.

RESULTS

We have shown that tumor signal intensities in T₂-weighted MR images decreased by an average of 20 ± 5% and T₂* relaxation times decreased by 14 ± 7 ms 24 h after intravenous administration of our MCL formulation. This compares to an average decrease in tumor signal intensity of 57 ± 12% and a T₂* relaxation time decrease of 27 ± 8 ms after the same time period with the aid of magnetic guidance.

CONCLUSION

MR and biodistribution analysis clearly show the efficacy of MCLs as MRI contrast agents, prove the use of magnetic guidance, and demonstrate the potential of MCLs as agents for imaging, guidance and therapeutic delivery.

Selection-migration regimes characterized by a globally stable equilibrium

The principle that a subdivided population subject to overdominance viability selection in each habitat will manifest a unique, globally attractng polymorphic equilibrium is posited. This follows as a corollary to the stronger principle that, if haploid selection or submultiplicative diploid selection (definition: the geometric mean of the homozygote viabilities is less than or equal to the heterozygote viability) is operating in each habitat,there is a unique, globally attracting stable equilibrium that may be monomorphic or polymorphic. These principles are proven for a broad spectrum of migration patterns. In all such migration selection systems, multiple fixation states cannot be simultaneously stable under submultiplicative viability regimes. Contrasting examples where submultiplicative viabilities are not in force are given.

Conjugation of bevacizumab to cationic liposomes enhances their tumor-targeting potential

Aims: Cationic liposomes have been shown to preferentially target the tumor vasculature, but not uniformly. Bevacizumab antibody selectively accumulates in tumors expressing VEGF. We thus developed bevacizumab-modified, pegylated cationic liposomes (PCLs) to improve the distribution of liposomes along tumor vessels, and to enhance tumor targeting. Materials & methods: We evaluated the delivery vehicle both in the absence and presence of VEGF, using human pancreatic cancer (Capan-1, HPAF-II and PANC-1) and endothelial (MS1-VEGF and HMEC-1) cell lines. Results: All cell lines except for HMEC-1 secreted VEGF. Modification of PCLs with bevacizumab did not alter ζ-potential, but increased overall liposome size. The toxicity profile for bevacizumab-modified PCLs was cell line dependent and, in general, bevacizumab improved cellular uptake and tumor targeting of PCLs. Conclusion: Bevacizumab-modified PCLs represent a potential improvement over the unmodified variety, supporting their future development for the treatment of cancer.

Mucin overexpression limits the effectiveness of 5-FU by reducing intracellular drug uptake and antineoplastic drug effects in pancreatic tumours

Current treatments for pancreatic cancer have failed to effectively manage the disease, and hence, more effective treatment approaches are urgently needed. Studies suggest that mucin O-glycosylation limits the cytotoxic effect of fluorouracil (5-FU) against the growth of human pancreatic cancer cells in vitro. In the present study, we investigated the relationship between the levels of mucin O-glycosylation expressed in pancreatic tumours and the antitumour effect of 5-FU. The inhibition of O-glycosylation was achieved by intratumoural (IT) injections of benzyl-alpha-GalNAc. Immunohistochemical staining of human pancreatic tumours revealed relatively high (Capan-1) and moderate (HPAF-II) expression levels of MUC1 mucin compared to MUC1 negative control (U-87 MG human glioblastoma) tumours. The antitumour effects of 5-FU (given systemically) against Capan-1 tumours improved significantly following IT injections of benzyl-alpha-GalNAc. Histochemical staining of tumour sections revealed a reduced number of neoplastic cells in tumours exposed to benzyl-alpha-GalNAc prior to 5-FU treatment compared to 5-FU alone. Furthermore, intracellular uptake of 5-FU by Capan-1 cells was significantly greater following injections of benzyl-alpha-GalNAc; however, no such effect was observed with U-87 MG cells. Mucin overexpression reduces intracellular drug uptake, antineoplastic and antitumour drug effects, which may have important clinical implications in treatment.

Mucin impedes cytotoxic effect of 5-FU against growth of human pancreatic cancer cells: overcoming cellular barriers for therapeutic gain

Mucins are high molecular weight glycoproteins expressed on the apical surface of normal epithelial cells. In cancer disease mucins are overexpressed on the entire cellular surface. Overexpression of MUC1 mucin in pancreatic tumours has been correlated with poor patient survival. Current chemotherapeutic approaches such as 5-fluorouracil (5-FU) has produced limited clinical success. In this study we investigated the role of mucin in cytotoxic drug treatment to determine whether the extracellular domain of mucin impedes cytotoxic drug action of 5-FU. Human pancreatic cancer cells revealed high and relatively moderate MUC1 levels for Capan-1 and HPAF-II, respectively, compared to MUC1 negative control (U-87 MG glioblastoma) that showed relatively non-specific anti-MUC1 uptake. Benzyl-alpha-GalNAc (O-glycosylation inhibitor) was used to reduce mucin on cell surfaces, and neuraminidase was used to hydrolyse sialic acid at the distal end of carbohydrate chains. Benzyl-alpha-GalNAc had no effect on cell morphology or proliferation at the concentrations employed. The inhibition of O-glycosylation resulted in significant 5-FU antiproliferative activity against Capan-1 and HPAF-II, but not against U-87 MG. However, the exposure of cells to neuraminidase failed to improve the cytotoxic action of 5-FU. Our experimental findings suggest that the overexpression of mucin produced by human pancreatic tumours might limit the effectiveness of chemotherapy.

The drug loading, cytotoxicty and tumor vascular targeting characteristics of magnetite in magnetic drug targeting

Chemotherapy is a popular treatment approach against cancer but significant uptake of drugs by normal tissues is still a major limitation. Magnetic drug targeting (MDT) has been used to improve localized drug delivery to interstitial tumor targets. MDT is now being developed to improve drug delivery to tumor vessels. We thus seek to understand the role of magnetite (MAG-C) in drug loading, influence on cytotoxicity and vascular targeting characteristics. The inclusion of MAG-C at lower concentrations (0.5 mg/ml) in cationic liposomes did not alter the efficiency of loading etoposide, but at higher concentrations (2.5 mg/ml) incorporation decreased from 80+/-3.4% to 44+/-4.26%. MAG-C reduced the incorporation of dacarbazine. The incorporation was significantly lower compared to liposomal etoposide, both in the presence and absence of MAG-C. The incorporation efficiency of vinblastine sulfate in cationic liposomes was similar for low and relatively high MAG-C content; values for incorporation were 21+/-0.11 and 23+/-2, respectively. Polyethylene-glycol improved the efficiency of loading chemotherapeutic agents regardless of drug type. Additionally, cytotoxicity and tumor vascular targeting characteristics of liposome therapeutics were not influenced by MAG-C. The components used to prepare magnetic liposomes for MDT should be optimized for maximum therapeutic benefit.

Coalescent size versus coalescent time with strong selection

This work studies the coalescent (ancestral pedigree, genealogy) of the entire population. The coalescent structure (topology) is robust, but selection changes the rate of coalescence (the time between branching events). The change in the rate of coalescence is not uniform, rather the reduction in the time between branching events is greatest when the coalescent is small (immediately after the common ancestor is the only member of the coalescent) with little change when the coalescent is large (immediately preceding when that common ancestor becomes fixed and the size of the coalescent is N). This provides that the reduction in the coalescent time due to selection is much greater than the reduction in the cumulative size of the coalescent (total number of ancestors of the present population after and including the most recent common ancestor) due to selection. If Ns>>1, the coalescent and fixation times are approximately equal to [Formula: see text] , which is much less than the value N which would result from neutral drift (N rather than the canonical haploid neutral fixation time 2N is the appropriate comparison for the model considered here), in particular, it is 70% less for Ns=10 and 95% less for Ns=100. However, for those values of Ns, and N ranging between 10(3) and 10(6), the reduction in the cumulative size of the coalescent of the entire population compared to the neutral case ranges from 17% to 65% (depending on the values of N and s). The coalescent time for two individuals for Ns of 10 and 100 is reduced by approximately 70% and 94%, respectively, compared with the neutral case. Because heterozygosity is proportional to the coalescent time for two individuals and the number of segregating alleles is proportional to the cumulative size of the coalescent, selection reduces heterozygosity more than it reduces the number of segregating alleles.

Development of 5-FU and Doxorubicin-Loaded Cationic Liposomes against Human Pancreatic Cancer: Implications for Tumor Vascular Targeting

PURPOSE

Human pancreatic adenocarcinoma is a major leading cause of cancer mortality in the United States. Given that current strategies are relatively ineffective against this disease, new treatments are being developed. Liposomes possessing relatively high cationic lipid content preferentially accumulate in tumor angiogenic vessels compared to vessels in normal tissues. We therefore seek to develop cationic liposomes for targeting pancreatic tumor vessels.

MATERIALS AND METHODS

We report development of 5-fluorouracil (5-FU) and doxorubicin hydrochloride (DOX) loaded in PEGylated cationic liposomes (PCLs). We evaluate cell association, intracellular fate, and cytotoxicity. Human pancreatic cancer cells HPAF-II and Capan-1, and endothelial cells HMEC-1 and HUVEC were used in this study. Intratumoral distribution of PCLs in (HPAF-II) tumors was determined by intravital microscopy.

RESULTS

HUVEC and HMEC-1 were most susceptible to 5-FU after 24 and 48 h, compared to HPAF-II and Capan-1. We observed >90% incorporation of 5-FU and DOX in PCLs for 3-20 mol% preparations, with reduced incorporation for >20 mol% formulations. PCLs showed significantly higher association with human endothelial versus pancreatic cancer cells, and improved growth inhibitory properties of DOX. Intravital microscopy revealed distribution of PCLs along HPAF-II vessels.

CONCLUSIONS

Targeting human pancreatic cancer with PCLs may represent a rational alternative to conventional strategies.

Development and characterization of magnetic cationic liposomes for targeting tumor microvasculature

Cationic liposomes preferentially target tumor vasculature compared to vessels in normal tissues. The distribution of cationic liposomes along vascular networks is, however, patchy and heterogeneous. To target vessels more uniformly we combined the electrostatic properties of cationic liposomes with the strength of an external magnet. We report part I of development. We evaluated bilayer physical properties of our preparations. We investigated interaction of liposomes with target cells including the role of PEG (polyethylene-glycol), and determined whether magnetic cationic liposomes can respond to an external magnetic field. The inclusion of relatively high concentration of MAG-C (magnetite) at 2.5 mg/ml significantly increased the size of cationic liposomes from 105+/-26.64 to 267+/-27.43 nm and reduced the zeta potential from 64.55+/-16.68 to 39.82+/-5.26 mv. The phase transition temperature of cationic liposomes (49.97+/-1.34 degrees C) reduced with inclusion of MAG-C (46.05+/-0.21 degrees C). MAG-C cationic liposomes were internalized by melanoma (B16-F10 and HTB-72) and dermal endothelial (HMVEC-d) cells. PEG partially shielded cationic charge potential of MAG-C cationic liposomes, reduced their ability to interact with target cells in vitro, and uptake by major RES organs. Finally, application of external magnet enhanced tumor retention of magnetic cationic liposomes.

Simulation of heating-compressed fast-ignition cores by petawatt laser-generated electrons

We report on unique particle-in-cell simulations to understand the relativistic electron beam thermalization and subsequent heating of highly compressed plasmas. The simulations yield heated core parameters in good agreement with the GEKKO-PW experimental measurements, given reasonable assumptions of laser-to-electron coupling efficiency and the distribution function of laser-produced electrons. The classical range of the hot electrons exceeds the mass density-core diameter product rhoL by a factor of several. Anomalous stopping appears to be present and is created by the growth and saturation of an electromagnetic filamentation mode that generates a strong back-EMF impeding hot electrons on the injection side of the density maxima.

PTEN enters the nucleus by diffusion

Despite much evidence for phosphatidylinositol phosphate (PIP)-triggered signaling pathways in the nucleus, there is little understanding of how the levels and activities of these proteins are regulated. As a first step to elucidating this problem, we determined whether phosphatase and tensin homolog deleted on chromosome 10 (PTEN) enters the nucleus by passive diffusion or active transport. We expressed various PTEN fusion proteins in tsBN2, HeLa, LNCaP, and U87MG cells and determined that the largest PTEN fusion proteins showed little or no nuclear localization. Because diffusion through nuclear pores is limited to proteins of 60,000 Da or less, this suggests that nuclear translocation of PTEN occurs via diffusion. We examined PTEN mutants, seeking to identify a nuclear localization signal (NLS) for PTEN. Mutation of K13 and R14 decreased nuclear localization, but these amino acids do not appear to be part of an NLS. We used fluorescence recovery after photobleaching (FRAP) to demonstrate that GFP-PTEN can passively pass through nuclear pores. Diffusion in the cytoplasm is retarded for the PTEN mutants that show reduced nuclear localization. We conclude that PTEN enters the nucleus by diffusion. In addition, sequestration of PTEN in the cytoplasm likely limits PTEN nuclear translocation.

Two-photon fluorescence correlation microscopy reveals the two-phase nature of transport in tumors

Transport parameters determine the access of drugs to tumors. However, technical difficulties preclude the measurement of these parameters deep inside living tissues. To this end, we adapted and further optimized two-photon fluorescence correlation microscopy (TPFCM) for in vivo measurement of transport parameters in tumors. TPFCM extends the detectable range of diffusion coefficients in tumors by one order of magnitude, and reveals both a fast and a slow component of diffusion. The ratio of these two components depends on molecular size and can be altered in vivo with hyaluronidase and collagenase. These studies indicate that TPFCM is a promising tool to dissect the barriers to drug delivery in tumors.

A logistic branching process for population genetics

A logistic (regulated population size) branching process population genetic model is presented. It is a modification of both the Wright-Fisher and (unconstrained) branching process models, and shares several properties including the coalescent time and shape, and structure of the coalescent process with those models. An important feature of the model is that population size fluctuation and regulation are intrinsic to the model rather than externally imposed. A consequence of this model is that the fluctuation in population size enhances the prospects for fixation of a beneficial mutation with constant relative viability, which is contrary to a result for the Wright-Fisher model with fluctuating population size. Explanation of this result follows from distinguishing between expected and realized viabilities, in addition to the contrast between absolute and relative viabilities.

Allosteric activation of PTEN phosphatase by phosphatidylinositol 4,5-bisphosphate

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is a tumor suppressor that is lost in many human tumors and encodes a phosphatidylinositol phosphate phosphatase specific for the 3-position of the inositol ring. Here we report a novel mechanism of PTEN regulation. Binding of di-C8-phosphatidylinositol 4,5-P2 (PI(4,5)P2) to PTEN enhances phosphatase activity for monodispersed substrates, PI(3,4,5)P3 and PI(3,4)P2. PI(5)P also is an activator, but PI(4)P, PI(3,4)P2, and PI(3,5)P2 do not activate PTEN. Activation by exogenous PI(4,5)P2 is more apparent with PI(3,4)P2 as a substrate than with PI(3,4,5)P3, probably because hydrolysis of PI(3,4)P2 yields PI(4)P, which is not an activator. In contrast, hydrolysis of PI(3,4,5)P3 yields a potent activator, PI(4,5)P2, creating a positive feedback loop. In addition, neither di-C4-PI(4,5)P2 nor inositol trisphosphate-activated PTEN. Hence, the interaction between PI(4,5)P2 and PTEN requires specific, ionic interactions with the phosphate groups on the inositol ring as well as hydrophobic interactions with the fatty acid chains, likely mimicking the physiological interactions that PTEN has with the polar surface head groups and the hydrophobic core of phospholipid membranes. Mutations of the apparent PI(4,5)P2-binding motif in the PTEN N terminus severely reduced PTEN activity. In contrast, mutation of the C2 phospholipid-binding domain had little effect on PTEN activation. These results suggest a model in which a PI(4,5)P2 monomer binds to PTEN, initiates an allosteric conformational change and, thereby, activates PTEN independent of membrane binding.

Cationic charge determines the distribution of liposomes between the vascular and extravascular compartments of tumors

Tumor vessels possess unique physiological features that might be exploited for improving drug delivery. In the present study, we investigate the possibility of modifying polyethylene glycol-ylated liposome cationic charge of polyethylene glycol coated liposomes to optimize delivery to tumor vessels using biodistribution studies and intravital microscopy. The majority of liposomes accumulated in the liver, and increasing charge resulted in lower retention in the spleen and blood. Although overall tumor uptake was not affected by charge in the biodistribution studies, intravital microscopy showed that increasing the charge content from 10 to 50 mol % doubled the accumulation of liposomes in tumor vessels, suggesting a change in intratumor distribution; no significant effect of charge on interstitial accumulation could be detected, possibly attributable to spatial heterogeneity. Increased vascular accumulation of cationic liposomes was similar in two different tumor types and sites. Our results suggest that optimizing physicochemical properties of liposomes that exploit physiological features of tumors and control the intratumor distribution of these drug carriers should improve vascular-specific delivery.

Propofol, a general anesthetic, promotes the formation of fluid phase domains in model membranes

The molecular site of anesthetic action remains an area of intense research interest. It is not clear whether general anesthetics act through direct binding to proteins or by perturbing the membrane properties of excitable tissues. Several studies indicate that anesthetics affect the properties of either membrane lipids or proteins. However, gaps remain in our understanding of the molecular mechanism of anesthetic action. Recent developments in membrane biology have led to the concept of small-scale domain structures in lipid and lipid--protein coupled systems. The role of such domain structures in anesthetic action has not been studied in detail. In the present study, we investigated the effect of anesthetics on lipid domain structures in model membranes using the fluorescent spectral properties of Laurdan (6-dodecanoyl-2-dimethylamino naphthalene). Propofol, a general anesthetic, promoted the formation of fluid domains in model membranes of dipalmitoyl phosphatidyl choline (DPPC) or mixtures of lipids of varying acyl chains (DPPC:DMPC dimyristoyl phosphatidyl choline 1:1). The estimated size of these domains is 20--50 A. Based on these studies, we speculate that the mechanism of anesthetic action may involve effects on protein--lipid coupled systems through alterations in small-scale lipid domain structures.

Influence of cationic lipids on the stability and membrane properties of paclitaxel-containing liposomes

Paclitaxel (taxol) is a poorly soluble anticancer agent that is in widespread clinical use. Liposomes provide a less toxic vehicle for solubilizing the drug and increasing the therapeutic index of paclitaxel in model tumor systems. The role of liposome membrane composition in the stability of paclitaxel-containing formulations is understood partially for neutral and anionic liposomes, but poorly for other compositions. We investigated the effect of dialkyl cationic lipids on the stability and physical properties of paclitaxel-containing liposomes, using circular dichroism (CD), fluorescence spectroscopy, and differential interference contrast microscopy (DIC). DOTAP (1,2-dioleoyl-3-trimethylammonium propane), a cationic lipid used frequently for gene delivery, was combined at various ratios with dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC), or distearoylphosphatidylcholine (DSPC). In the absence of DOTAP, the stability of liposomes containing > or =3 mol% paclitaxel was observed to follow the following rank order: DPPC >DSPC > DMPC. Increasing concentrations of DOTAP increased the physical stability of all compositions, and maximal stabilization was achieved at 30-50 mol% DOTAP, depending on the paclitaxel concentration and the acyl chain length of the phosphatidylcholine. The relationship between stability and mole fraction of DOTAP was complex for some compositions. DOTAP exerted a major fluidizing effect on DMPC, DPPC, and DSPC membranes, and the addition of paclitaxel at 3-8 mol% did not increase fluidity further. Studies of membrane phase domain behavior using the probe Laurdan (6-dodecanoyl-2-dimethylaminonaphthalene) indicated that both paclitaxel and DOTAP were miscible with the phosphatidylcholine phase. The physical events leading to destabilization of formulations are hypothesized to arise from concentration-dependent paclitaxel self-association rather than immiscibility of the membrane lipids. Given the increased incorporation and stability of paclitaxel in DOTAP-containing membranes and the potential for enhanced interaction with cells, cationic liposomes may provide a therapeutic advantage over previously described liposome formulations.

John Graunt, John Arbuthnott, and the human sex ratio

John Graunt was the first person to compile data that showed an excess of male births over female births. He also noticed spatial and temporal variation in the sex ratio, but the variation in his data is not significant. John Arbuthnott was the first person to demonstrate that the excess of male births is statistically significant. He erroneously concluded that there is less variation in the sex ratio than would occur by chance, and asserted without a basis that the sex ratio would be uniform over all time and space.

In vivo measurement of gene expression, angiogenesis and physiological function in tumors using multiphoton laser scanning microscopy

Intravital microscopy coupled with chronic animal window models has provided stunning insight into tumor pathophysiology, including gene expression, angiogenesis, cell adhesion and migration, vascular, interstitial and lymphatic transport, metabolic microenvironment and drug delivery. However, the findings to date have been limited to the tumor surface (< 150 microm). Here, we show that the multiphoton laser-scanning microscope can provide high three-dimensional resolution of gene expression and function in deeper regions of tumors. These insights could be critical to the development of novel therapeutics that target not only the tumor surface, but also internal regions.

Phospholipid-cationic lipid interactions: influences on membrane and vesicle properties

Liposomes composed of synthetic dialkyl cationic lipids and zwitterionic phospholipids such as dioleoylphosphatidylethanolamine have been studied extensively as vehicles for gene delivery, but the broader potentials of these cationic liposomes for drug delivery have not. An understanding of phospholipid-cationic lipid interactions is essential for rational development of this potential. We evaluated the effect of the cationic lipid DOTAP (N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium) on liposome physical properties such as size and membrane domain structure. DSC (differential scanning calorimetry) showed progressive decrease and broadening of the phase transition temperature of dipalmitoylphosphatidylcholine (DPPC) with increasing fraction of DOTAP, in the range of 0.4-20 mol%. Laurdan (6-dodecanolyldimethylamino-naphthalene), a fluorescent probe of membrane domain structure, showed that DOTAP and DPPC remained miscible at all ratios tested. DOTAP reduced the size of spontaneously-forming PC-containing liposomes, regardless of the acyl chain length and degree of saturation. The anionic lipid DOPG (dioleoylphosphatidylglycerol) had similar effects on DPPC membrane fluidity and size. However, DOTAP/DOPC (50/50) vesicles were taken up avidly by OVCAR-3 human ovarian tumor cells, in contrast to DOPG/DOPC (50/50) liposomes. Overall, DOTAP exerts potent effects on bilayer physical properties, and may provide advantages for drug delivery.

Role of tumor-host interactions in interstitial diffusion of macromolecules: cranial vs. subcutaneous tumors

The large size of many novel therapeutics impairs their transport through the tumor extracellular matrix and thus limits their therapeutic effectiveness. We propose that extracellular matrix composition, structure, and distribution determine the transport properties in tumors. Furthermore, because the characteristics of the extracellular matrix largely depend on the tumor-host interactions, we postulate that diffusion of macromolecules will vary with tumor type as well as anatomical location. Diffusion coefficients of macromolecules and liposomes in tumors growing in cranial windows (CWs) and dorsal chambers (DCs) were measured by fluorescence recovery after photobleaching. For the same tumor types, diffusion of large molecules was significantly faster in CW than in DC tumors. The greater diffusional hindrance in DC tumors was correlated with higher levels of collagen type I and its organization into fibrils. For molecules with diameters comparable to the interfibrillar space the diffusion was 5- to 10-fold slower in DC than in CW tumors. The slower diffusion in DC tumors was associated with a higher density of host stromal cells that synthesize and organize collagen type I. Our results point to the necessity of developing site-specific drug carriers to improve the delivery of molecular medicine to solid tumors.

The coalescent time in the presence of background fertility selection

Selection ultimately entails differential reproductive success over several generations. This can be measured as a correlation of the number of progeny an individual has with the number of progeny its parent had. This correlation could have a genetic or a cultural basis. The effect of such a correlation is to multiply the single generation sampling variance (Vdeltap) in the diffusion approximation for fixation time by (1-b)+bx(1+r)/(1-r), where bxrn is the correlation between the number of progeny of an individual and its ancestor n generations ago (e.g., b is the heritability and br is the resultant parent-offspring progeny number correlation if the progeny number is genetically determined). This results in a reduction of the fixation or coalescent time by division by this factor. Sex differences in this correlation have been observed, and this provides an explanation for the difference of coalescent times of y-chromosomes and mitochondria.

Exercise without dietary restriction as a means to long-term fat loss in the obese cardiac patient

BACKGROUND

To examine the effects of a 12-month daily walking program without dietary restriction on the metabolic rate, body composition and blood lipid profile of overweight and moderately obese patients following myocardial infarction.

METHODS

DESIGN

longitudinal training (preliminary study).

SETTING

out-patient cardiac rehabilitation program.

PARTICIPANTS

twelve consecutive volunteers (8M, 4F) with a body mass index of 25-40 kg/m2. Relative to average cardiac patients, the men but not the women were significantly heavier (100.8 vs 77.4 kg [M], 70.7 vs 74.2 kg [F]) and fatter (hydrostatic estimate of body fat 34.0% vs 23.1% [M]; 38.3% vs 36.3% [F]) than the general cardiac patient.

MEASURES

body mass, hydrostatic weighing, triglycerides, total, HDL- and LDL-cholesterol, resting and peak oxygen intake, one week food intake diaries.

RESULTS

Daily walking increased progressively from 20 min to 43 min over 3 months, and was then held constant for 9 months. Peak aerobic power increased 24%, from 19.9 to 24.6 ml/[kg.min] (p < 0.001). Resting oxygen intake rose from 3.1 to 3.4 ml/[kg.min], (p < 0.05). Energy intake increased from 6.10 to 6.57 MJ/day, but body mass decreased by an average of 4.5 kg (p < 0.05, 4.1 kg [M], 5.1 kg [F]), and body fat content diminished from 35.4 to 33.2% (p < 0.02, 1.8% [M], 3.2% [F]), with no change in lean body mass (57.7 vs 57.8 kg). Triglycerides diminished from 2.63 to 2.28 mmol/L (p < 0.005). Total and LDL-cholesterol also tended to change favorably (from 6.15 to 5.80 and 4.44 to 3.80 mmol/L respectively, but HDL-cholesterol was unchanged).

CONCLUSIONS

A daily walking program without dietary restriction induces a favorable change in body composition and lipid profile in moderately obese cardiac patients. An exercise-induced increase of resting metabolism apparently makes an important contribution to this outcome.

Influence of steroid injection on ligament healing in the rat

The effect of a single local injection of long acting corticosteroid on the healing of acute rat medial collateral ligament injuries was studied. The medial collateral ligaments of 81 adult female rats were exposed surgically. In 32 rats, the ligament was transected sharply, the overlying muscle was closed, and a human equivalent dose of dexamethasone was injected under the muscle layer, bathing the injured ligament. The identical operation with no corticosteroid injection was done in 32 additional rats: in the remaining 17 animals, the incision was closed without ligament transection or injection. The rats were divided into 3 groups of 25. Each group consisted of 10 rats that were injected, 10 that were not injected, and 5 that underwent sham operations. One group was euthanized 6 days after surgery, 1 group after 10 days, and 1 group after 20 days. Histologic evaluation and biomechanical testing were performed for each subgroup. A cellular pathologist examined a smaller group of 6 rats (2 from each group) for histologic changes 40 days after surgery. No histologic differences were noted between the injected and noninjected ligaments 6, 10, or 20 days after injury. At 40 days, the injected specimens showed a slightly more mature crimp pattern than the noninjected specimens. Mechanical testing demonstrated no significant difference in ultimate load or ultimate stress between the injected and noninjected groups. There were no detrimental effects of a single dose administration of dexamethasone on the histologic appearance or biomechanical strength of healing rat medial collateral ligaments.

The effect of mating structure and progeny distribution on heterozygosity versus the number of alleles as measures of variation

Heterozygosity and the number of alleles are both measures of the genetic variation of a population. They are qualitatively similar if the distribution of the number of progeny is Poisson, but not necessarily for other distributions. In particular, selfing decreases heterozygosity and also decreases the number of alleles when the progeny distribution is Poisson, but decreases heterozygosity and increases the number of alleles when there are two progeny per individual. This is because heterozygosity is closely related to the breeding structure (inbreeding) of the population, whereas the number of alleles is more influenced by the variation of the sampling process. Branching processes are employed to model the dynamics of mutant alleles, with drift and subsequent mutation contributing to extinction. In populations of four individuals, double first cousin mating has greater heterozygosity, but fewer alleles, than half-sib mating.

Genetic interactions and dosage effects of Polycomb group genes of Drosophila

The Polycomb (Pc) group of genes are required for maintenance of cell determination in Drosophila melanogaster. At least 11 Pc group genes have been described and there may be up to 40; all are required for normal regulation of homeotic genes, but as a group, their phenotypes are rather diverse. It has been suggested that the products of Pc group genes might be members of a heteromeric complex that acts to regulate the chromatin structure of target loci. We examined the phenotypes of adult flies heterozygous for every pairwise combination of Pc group genes in an attempt to subdivide the Pc group functionally. The results support the idea that Additional sex combs (Asx), Pc, Polycomblike (Pcl), Posterior sex combs (Psc), Sex combs on midleg (Scm), and Sex combs extra (Sce) have similar functions in some imaginal tissues. We show genetic interactions among extra sex combs (esc) and Asx, Enhancer of Pc, Pcl, Enhancer of zeste E(z), and super sex combs and reassess the idea that most Pc group genes function independently of esc. Most duplications of Pc group genes neither exhibit anterior transformations nor suppress the extra sex comb phenotype of Pc group mutations, suggesting that not all Pc group genes behave as predicted by the mass-action model. Surprisingly, duplications of E(z) enhance homeotic phenotypes of esc mutants. Flies with increasing doses of esc+ exhibit anterior transformations, but these are not enhanced by mutations in trithorax group genes. The results are discussed with respect to current models of Pc group function.