Six-month outcomes on A1C and cardiovascular risk factors in patients with type 2 diabetes treated with exenatide in an ambulatory care setting

AIM

This study evaluated changes in clinical effectiveness measures of patients with type 2 diabetes initiating exenatide therapy in a real-world setting.

METHODS

Eligible patients identified in the General Electric (GE) electronic medical record (EMR) research database from 1 January 2000 through 31 December 2007 were > or =18 years old with type 2 diabetes. Patients had prescription orders in the previous 395 days for metformin, a sulfonylurea, or a thiazolidinedione as monotherapy or in combination, and had at least 6 months of follow-up activity. Baseline clinical measures were documented from 45 days prior up to 15 days after exenatide initiation and follow-up measures documented at 6 months +/- 45 days.

RESULTS

A total of 1709 patients were identified for study inclusion. The overall mean A1C reduction (s.e.m.) at 6 months was -0.8% (0.05) (p<0.001), weight loss was -3.2 kg (0.14) (p<0.001), blood pressure (BP) lowering was -1.9 mmHg (0.46) systolic blood pressure (SBP) (p<0.001) and -0.5 mmHg (0.27) diastolic blood pressure (DBP) (p = 0.078). Changes in low-density lipoprotein (LDL), triglycerides and HDL were -7.4 mg/dl (1.7) (p<0.001), -23.2 mg/dl (6.7) (p = 0.001) and -0.8 mg/dl (0.33) (p = 0.012) respectively. In a quartile analysis by weight loss, mean A1C reduction ranged from -1.1 to -0.65% in the highest to lowest weight loss quartiles respectively.

CONCLUSIONS

In a real-world setting, exenatide initiation is associated with significant improvements in the measures of clinical effectiveness for type 2 diabetes. These reductions were comparable to those reported in randomized, controlled registration trials after 6 months of therapy.

Mathematical modeling shows exenatide improved beta-cell function in patients with type 2 diabetes treated with metformin or metformin and a sulfonylurea

The incretin mimetic exenatide improved glycemic control and reduced body weight in patients with type 2 diabetes inadequately controlled with metformin+/-a sulfonylurea. We assessed postprandial beta-cell function by mathematical modeling, independent of confounding effects from differing ambient glucose levels among treatments. Subjects were 63% males, 55+/-10 years, BMI 33+/-6 kg/m2, HbA1C 8.1+/-1.1% (+/- SD) randomized to 5 microg exenatide or placebo twice daily for 4 weeks. Subsequently, one arm remained at 5 microg twice daily, one arm escalated to 10 microg twice daily, and one treatment arm remained on placebo for 26 weeks. Subjects continued metformin+/-a sulfonylurea. A subset with meal tests at baseline and week 30 were analyzed (n=73). Outcome measures were the model-based beta-cell function parameters dose-response relating insulin secretion to glucose concentration, rate sensitivity, and potentiation. Exenatide reduced postprandial glucose excursions. Modeling predicted an upward shift of the beta-cell dose-response. Model-predicted insulin secretion rate at a reference glucose concentration increased 72% (10 microg), increased 40% (5 microg), or decreased 21% (placebo) at week 30 [ p=0.015 (10 microg); p=0.045 (5 microg); vs. placebo]. At week 30, the 2-hour post-meal to basal potentiation factor ratio was increased to 1.53+/-0.10 (10 microg; p=0.0142 vs. placebo) or 1.40+/-0.08 (5 microg; p=0.0402 vs. placebo) compared with 1.15+/-0.06 (placebo). Exenatide caused an upward shift of the beta-cell dose-response and enhanced potentiation of insulin secretion. This model suggests exenatide improved beta-cell function in patients with type 2 diabetes treated with metformin+/-a sulfonylurea.

Long-term effects of exenatide therapy over 82 weeks on glycaemic control and weight in over-weight metformin-treated patients with type 2 diabetes mellitus

AIM

The ability of the incretin mimetic exenatide to improve glycaemic control and reduce body weight was assessed over 82 weeks in patients with type 2 diabetes failing to achieve glycaemic control with maximally effective doses of metformin.

METHODS

In this interim 82-week analysis, 150 (total cohort) of an eligible population of 183 patients opted to continue exenatide treatment in an uncontrolled open-label extension of a 30-week double-blind, placebo-controlled trial. Of these, 92 patients (completer cohort) achieved 82 weeks of exenatide therapy. Patients continued metformin throughout the study.

RESULTS

At the end of the placebo-controlled trial, exenatide resulted in an haemoglobin A1c (HbA1c) reduction from baseline of -1.0 +/- 0.1% (mean +/- SE) (exenatide treatment arms), with durable HbA1c reductions after 82 weeks of -1.3 +/- 0.1%. The percent of patients who achieved HbA1c < or = 7% at weeks 30 and 82 was 46 and 59% respectively. After 30 weeks, exenatide caused a reduction in weight from baseline of -3.0 +/- 0.6 kg, with a progressive reduction in weight of -5.3 +/- 0.8 kg after 82 weeks. In addition, exenatide treatment produced clinically significant improvements in cardiovascular risk factors after 82 weeks. The most frequent adverse event after 30 and 82 weeks of exenatide was nausea, which was generally of mild-or-moderate intensity. It decreased in incidence after initiation in the controlled trial and the uncontrolled open-label extension. Hypoglycaemia was rare, with no severe events.

CONCLUSION

Exenatide was generally well tolerated, producing a durable reduction in HbA1c and a progressive reduction in weight over 82 weeks in patients with type 2 diabetes failing to achieve glycaemic control with metformin.

Day-long subcutaneous infusion of exenatide lowers glycemia in patients with type 2 diabetes

Exenatide (exendin-4) is an incretin mimetic with potential antidiabetic activity. This study examined the effects of a continuous subcutaneous (SC) infusion of exenatide (0.2, 0.4, 0.6, or 0.8 microg/kg/day) or placebo (PBO) on glycemic control over 23 h intervals. Twelve subjects with type 2 diabetes treated with metformin and/or diet received 10 infusions (4 exenatide, 6 PBO) on consecutive days. Exenatide was given in a dose-increasing design with at least one placebo infusion between each exenatide infusion, and with meals and a snack provided during the first 14 h of infusion. Plasma exenatide concentrations were dose-proportional. Plasma glucose (4-23 h) was lower in all exenatide arms compared to placebo (p<0.0001). The change in insulin/glucagon ratio and amylin concentrations from pre-infusion to post-infusion was increased (p<0.005, p<0.05, respectively) in the combined exenatide arms, but remained unchanged in the placebo groups. Nausea and vomiting were the most common treatment emergent adverse events. Exenatide infusion also appeared to have positive effects on beta-cell and alpha-cell function as measured by proinsulin/insulin ratios and mean glucagon concentrations. In summary, exenatide lowered plasma glucose during both prandial and fasting states when delivered as a continuous SC infusion over twenty-three hours, suggesting that exenatide can provide day-long glycemic control in patients with type 2 diabetes.

Dose-response for glycaemic and metabolic changes 28 days after single injection of long-acting release exenatide in diabetic fatty Zucker rats

AIMS/HYPOTHESIS

Exenatide (exendin-4) injected subcutaneously twice daily reduces glycaemic deterioration in diabetic fatty Zucker (ZDF) rats and reduces HbA1c in humans with type 2 diabetes. Because tachyphylaxis may develop with continuous peptide exposure, we examined the activity of a long-acting-release (LAR) formulation of exenatide on HbA1c, insulin sensitivity and beta cell secretion in ZDF rats.

METHODS

Single subcutaneous injections of a poly-lactide-glycolide microsphere suspension (3% peptide) containing 0, 1, 10, 100, 1,000, 3,000 or 9,000 mug exenatide were administered to 9-week-old ZDF rats with matched initial HbA1c values (n=7 rats/group).

RESULTS

In contrast to the progressive 3.22+/-0.42% increase in HbA1c in control ZDF rats observed over 28 days, single exenatide-LAR injections dose-proportionally prevented such glycaemic deterioration (median effective dose 74 microg+/-0.1 log per rat; median effective concentration 52 pmol/l+/-0.06 log). Hyperinsulinaemic-euglycaemic clamp procedures incorporating an intraclamp glucose challenge performed 28 days after treatment revealed increases in beta cell response to the glucose challenge at lower exenatide-LAR doses, and up to a 2.1-fold increase in insulin sensitivity at higher exenatide-LAR doses.

CONCLUSIONS/INTERPRETATION

The finding that a single dose of exenatide-LAR enhanced glucose control for 28 days in the ZDF rat model of type 2 diabetes suggests that tachyphylaxis is unlikely to be a feature of exenatide-LAR preparations, and supports further clinical exploration.

Evaluation of endostatin antiangiogenesis gene therapy in vitro and in vivo

Progressive growth and metastasis of solid tumors require angiogenesis, or the formation of new blood vessels. Endostatin is a 20-kDa carboxy-terminal fragment of collagen XVIII that has been shown to inhibit endothelial cell proliferation and tumor angiogenesis. Replication-deficient recombinant adenovirus (rAd) vectors were constructed, which encoded secreted forms of human and mouse endostatin (HECB and MECB, respectively), and, as a control, human alkaline phosphatase (APCB). Accumulation of endostatin was demonstrated in supernatants of cultured cells infected with the endostatin rAds. These supernatants disrupted tubule formation, inhibited migration and proliferation, and induced apoptosis in human dermal vascular endothelial cells or human vascular endothelial cells. Endostatin-containing supernatants had no effect on the proliferation of MidT2-1 mouse mammary tumor cells in vitro. A pharmacokinetic study of MECB in immunocompetent FVB mice demonstrated a 10-fold increase of serum endostatin concentrations 3 days after intravenous administration of 1x10(10) particles of this rAd (215-257 ng/mL compared to 12-38 ng/mL in control rAd-treated mice). Intravenous administration of MECB reduced b-FGF stimulated angiogenesis into Matrigel plugs by 38%. Intratumoral MECB inhibited growth of MidT2-1 syngeneic mammary tumors in FVB mice, but had minimal impact on the growth of MDA-MB-231 human breast tumors in SCID mice. Intravenous therapy with MECB also initially inhibited growth of MidT2-1 tumors, but this activity was subsequently blocked by induced anti-rAd antibodies. In summary, endostatin gene therapy effectively suppressed angiogenic processes in vitro and in vivo in several model systems.

The role of natural killer cells in adenovirus-mediated p53 gene therapy

Adenovirus-mediated gene therapy is a promising new approach for treatment of ovarian cancer. In animal models, complete elimination of cancer cells is often achieved, although the therapeutic gene has not been delivered to all these cells. This is referred to as a bystander effect, because tumor cells near those that receive the therapeutic gene are also eliminated. Several mechanisms have been proposed for the bystander effect, including intercellular communication within the tumor via gap junctions, apoptosis, antiangiogenesis, cytokines or other soluble mediators, and immunological mechanisms. There are two well-documented antitumor effector cell populations in athymic nude mice: macrophages and natural killer (NK) cells. We hypothesize that peritoneal populations of NK cells in nude mice treated with adenoviruses are involved in the observed bystander effect in this in vivo model. We investigated the role of NK cells as immunological mediators for the bystander effect using the p53 tumor suppressor as the therapeutic anticancer gene. Most ovarian cancer cell lines tested were sensitive to lysis by NK cells, although different ovarian cancer cell lines exhibited different sensitivities to NK cell-mediated lysis. To determine the importance of NK cells in the overall efficacy and in the bystander effect of gene therapy, NK cells were depleted in mice by administration of anti-NK1.1 monoclonal antibodies. To study the efficacy of NK depletion, C57BL/6 (nu/nu) mice were given injections i.v. by a single tail vein injection or i.p. with increasing doses of anti-NK1.1 IgG. All doses of anti-NK1.1 antibody, from 100-500 micrograms, essentially eliminated cytotoxic NK activity. To assess the duration of depletion after a single dose of anti-NK1.1 IgG, a time-course experiment was performed. NK 1.1 antibody was effective in completely depleting cytotoxic NK cell activity in the mice for up to 7 days, whether given as 500 micrograms (i.p.) or 200 micrograms (i.v.). Flow cytometric analysis performed on peritoneal cell populations confirmed depletion of NK cells by approximately 80%. Finally, a survival study was performed, in which animals were depleted of NK cells. In this experiment, NK cell-depleted mice were injected with anti-NK1.1 IgG, and control mice were mice were treated with normal saline. Two days later, all mice were inoculated with a lethal i.p. dose of NIH:OVCAR-3 ovarian cancer cells. After 3 days, the mice were divided into two treatment groups; one treatment group received three consecutive daily i.p. injections of Ad-CMV-p53 (SCH58500), and the second treatment group received three consecutive daily i.p. injections of control adenovirus construct, rAd-null. All of the NK cell-depleted animals, whether treated with rAd-null or with Ad-CMV-p53 (SCH58500) were dead of disease by 116 and 138 days, respectively, after initiation of adenovirus treatment, and no statistically significant difference in survival was observed (P = 0.349). A significant survival advantage was seen in control (NK-competent) mice treated with rAd-null (P = 0.04), although all were dead of disease by day 184. Importantly, control NK-competent mice treated with Ad-CMV-p53 (SCH58500) showed no tumor growth or ascites production, and all animals survived. These results indicate that immunological mechanisms involving natural killer cells play an important role in the bystander effect involving adenovirus-p53 gene therapy for ovarian cancer.

Efficient assembly of recombinant major histocompatibility complex class I molecules with preformed disulfide bonds

The expression of major histocompatibility class I (MHC-I) crucially depends upon the binding of appropriate peptides. MHC-I from natural sources are therefore always preoccupied with peptides complicating their purification and analysis. Here, we present an efficient solution to this problem. Recombinant MHC-I heavy chains were produced in Escherichia coli and subsequently purified under denaturing conditions. In contrast to common practice, the molecules were not reduced during the purification. The oxidized MHC-I heavy chain isoforms were highly active with respect to peptide binding. This suggests that de novo folding of denatured MHC-I molecules proceed efficiently if directed by preformed disulfide bond(s). Importantly, these molecules express serological epitopes and stain specific T cells; and they bind peptides specifically. Several denatured MHC-I heavy chains were analyzed and shown to be of a quality, which allowed quantitative analysis of peptide binding. The analysis of the specificity of the several hundred human MHC haplotypes, should benefit considerably from the availability of pre-oxidized recombinant MHC-I.

Orally bioavailable farnesyltransferase inhibitors as anticancer agents in transgenic and xenograft models

The in vivo evaluation process described here was instrumental in the identification of SCH 66336 as a clinical candidate. Our lead FTI, SCH 66336, and several other FTIs are being evaluated in early-phase clinical trials to establish proof-of-principle for farnesyl transferase inhibition in human patients. The preclinical studies described here suggest that FTIs may have utility against a wide array of human cancers as a single agent and may, at least in some cases, lead to tumor regression. In addition, the results to date in combination with cytotoxic chemotherapeutic agents in animal models indicate that these combinations may enhance the clinical efficacy of FPT inhibitors. Further preclinical studies should help to guide the clinical development of this class of novel antitumor agents.

Enhanced apoptotic activity of a p53 variant in tumors resistant to wild-type p53 treatment

TP53 is the most commonly altered tumor-suppressor gene in cancer and is currently being tested in Phase II/III gene replacement trials. Many tumors contain wild-type TP53 sequence with elevated MDM2 protein levels, targeting p53 for degradation. These tumors are more refractory to treatment with exogenous wild-type p53. Here we generate a recombinant adenovirus expressing a p53 variant, rAd-p53 (d 13-19), that is deleted for the amino acid sequence necessary for MDM2 binding (amino acids 13-19). We compared the apoptotic activity of rAd-p53 (d 13-19) with that of a recombinant adenovirus expressing wild-type p53 (rAd-p53) in cell lines that differ in endogenous p53 status. rAd-p53 (d 13-19) caused higher levels of apoptosis in p53 wild-type tumor lines compared with wild-type p53 treatment, as measured by annexin V-FITC staining. In p53-altered tumor lines, rAd-p53 (d 13-19) showed apoptotic activity similar to that seen with wild-type p53 treatment. In normal cells, no increase in cytopathicity was detected with rAd-p53 (d 13-19) compared with wild-type p53 treatment. This variant protein displayed synergy with chemotherapeutic agents to inhibit proliferation of ovarian and breast cell lines. The p53 variant showed greater antitumor activity in an established p53 wild-type tumor compared with treatment with wild-type p53. The p53 variant represents a means of expanding TP53 gene therapy to tumors that are resistant to p53 treatment due to the cellular responses to wild-type p53.

The farnesyl protein transferase inhibitor SCH66336 synergizes with taxanes in vitro and enhances their antitumor activity in vivo

PURPOSE

SCH66336 is an orally active, farnesyl protein transferase inhibitor. SCH66336 inhibits ras farnesylation in tumor cells and suppresses tumor growth in human xenograft and transgenic mouse cancer models in vivo. The taxanes, paclitaxel (Taxol) and docetaxel (Taxotere) block cell mitosis by enhancing polymerization of tubulin monomers into stabilized microtubule bundles, resulting in apoptosis. We hypothesized that anticancer combination therapy with SCH66336 and taxanes would be more efficacious than single drug therapy.

METHODS

We tested the efficacy of SCH66336 and taxanes when used in combination against tumor cell proliferation in vitro, against NCI-H460 human lung tumor xenografts in nude mice, and against mammary tumors in wap-ras transgenic mice.

RESULTS

SCH66336 synergized with paclitaxel in 10 out of 11 tumor cells lines originating from breast, colon, lung, ovary, prostate, and pancreas. SCH66336 also synergized with docetaxel in four out of five cell lines tested. In the NCI-H460 lung cancer xenograft model, oral SCH66336 (20 mg/kg twice daily for 14 days) and intraperitoneal paclitaxel (5 mg/kg once daily for 4 days) caused a tumor growth inhibition of 56% by day 7 and 65% by day 14 compared to paclitaxel alone. Male transgenic mice of the wap-ras/F substrain [FVB/N-TgN(WapHRAS)69LlnYSJL] spontaneously develop mammary tumors at 6 9 weeks of age which have been previously shown to be resistant to paclitaxel. Paclitaxel resistance was confirmed in the present study, while SCH66336 inhibited growth of these tumors. Most importantly, SCH66336 was able to sensitize wap-ras/F mammary tumors to paclitaxel chemotherapy.

CONCLUSION

Clinical investigation of combination therapy using SCH66336 and taxanes in cancer patients is warranted. Further, SCH66336 may be useful for sensitizing paclitaxel-resistant tumors to taxane treatment.

Derivation and initial characterization of a mouse mammary tumor cell line carrying the polyomavirus middle T antigen: utility in the development of novel cancer therapeutics

Here we describe the derivation of novel cell lines from spontaneous mammary tumors that arose in mouse mammary tumor virus-polyomavirus (MMTV-PyV) Middle T (MidT) transgenic mice. Clonal cell lines from four mixed cell populations were tested for adenovirus transducibility and sensitivity to p53 tumor suppressor gene therapy mediated by SCH58500, a replication-deficient adenovirus that expresses human p53. The MidT2-1 cell line was selected for further characterization in vitro and in vivo. This cell line carried the PyV MidT antigen, had wild-type p53 DNA, and was sensitive to suppression of proliferation by MMAC/PTEN tumor suppressor gene therapy. MidT2-1 cells gave rise to highly aggressive tumors in syngeneic FVB mice in both the mammary fat pad and the peritoneal cavity. The histopathology of MidT2-1 tumors closely resembled the histopathology of the primary transgenic tumors. Tumor growth in vivo was inhibited by p53 gene therapy or by MMAC gene therapy. In addition, combination therapy with a number of anticancer agents had synergistic or additive efficacy in vitro. In particular, MMAC gene therapy synergized with SCH58500 or paclitaxel. In the i.p. MidT2-1 tumor model p53 gene therapy enhanced the survival benefits of paclitaxel/cisplatin chemotherapy. Combination therapy has become a mainstay in cancer treatment. In this report, we use a novel transgenic mouse tumor cell line to suggest new combinations that might be explored in clinical cancer care. These include gene therapy using the tumor suppressors MMAC and p53, chemotherapy using farnesyl transferase inhibitors, the microtubule stabilizing taxanes, and the DNA synthesis disruptors gemcitabine and cisplatin. The precise biological mechanisms by which these therapies induce their antitumor effects are not fully elucidated. However, the work presented here suggests that many of these therapeutic approaches have synergistic antitumor activity when used in combination.

Combination therapy with SCH58500 (p53 adenovirus) and cyclophosphamide in preclinical cancer models

SCH58500 (ACN53) is a replication-deficient, recombinant adenovirus which expresses human p53 tumor suppressor. In preclinical models, SCH58500 has therapeutic efficacy against a wide range of human tumor types containing nonfunctional p53 and it has enhanced activity in combination with many chemotherapeutic drugs. However, the anti-tumor efficacy of SCH58500 combined with the DNA-damaging chemotherapeutic cyclophosphamide has not been previously reported. Cyclophosphamide did not enhance the activity of SCH58500 in three out of four human tumor xenograft models studied. Furthermore, combination therapy with SCH58500 and cyclophosphamide was not any better than single drug treatment in transgenic H-ras mice and in FVB mice bearing syngeneic MidT2-1 tumors. This is in sharp contrast to previous combination studies in these models where SCH58500 had enhanced efficacy when given with the farnesyl protein transferase inhibitor SCH66336, paclitaxel, cisplatin, cisplatin/paclitaxel, or doxorubicin. Further evaluation of this combination is required before it can be recommended for clinical trials in cancer patients.

Development and validation of sensitive assays to quantitate gene expression after p53 gene therapy and paclitaxel chemotherapy using in vivo dosing in tumor xenograft models

SCH58500 (ACN53) is a replication-deficient, type 5 adenovirus (Ad) expressing human wild-type p53 tumor suppressor. It is currently undergoing clinical trials as a cancer therapeutic. Many SCH58500 clinical trials incorporate an arm comparing traditional chemotherapy against chemotherapy combined with SCH58500. Paclitaxel was chosen for combination therapy in the preclinical study reported here due to its extensive use as a first-line therapy in ovarian cancer, its synergy with SCH58500 in preclinical cancer models, and its activation of p53-independent apoptosis, which might result in a "lowered threshold" for tumor cell death. SCID mice bearing human tumor xenografts were dosed with intratumoral vehicle, control Ad vector, or SCH58500, with or without paclitaxel. Real-time quantitative reverse transcriptase polymerase chain reaction assays were developed and validated to quantitate expression of p53, the p53 downstream effector gene p21, and the apoptosis-related genes, bax, bcl-2, and survivin. Protein expression was confirmed using immunohistochemical assays for p53 and p21. Only tumors injected with SCH58500 had detectable levels of exogenous p53 DNA and mRNA. After SCH58500 treatment, 3-11-fold elevations of p21 expression were observed in tumor xenografts containing nonfunctional p53 (MDA-MB-468, MDA-MB-231, MIAPaCa2, DU-145, and SK-OV-3), but no change in p21 mRNA in wild-type p53 PA-1 tumors. Immunohistochemical assays confirmed induction of p21 protein in MDAMB-468 and SK-OV-3 cells, but not in PA-1 cells. Ad vector alone or paclitaxel alone had no effect on p21 mRNA levels in most tumors. However, paclitaxel suppressed p21 expression induced by SCH58500 4-fold in DU-145 and SK-OV-3 tumors. Paclitaxel also affected expression of the housekeeping gene gapdh. There was no consistent pattern to the changes in bax, bcl-2, or survivin after SCH58500 treatment with or without paclitaxel between tumor types, although there were consistent responses within individual tumor lines. The mRNA ratios for bax/bcl-2 and bax/survivin were also not informative across tumor types. Of the genes examined, only p21 gave a predictable response 24 hours after p53 gene therapy and therefore, p21 expression may be useful for confirming SCH58500 activity in human tumor biopsies.

NK cells mediate the anti-tumor effects of E1-deleted, type 5 adenovirus in a human tumor xenograft model

SCH58500 (ACN53) is a recombinant adenovirus expressing human p53 for gene therapy of cancer. In preclinical studies, SCH58500 has shown efficacy against many tumor-types with non-functional p53. This activity arises from both p53-mediated and adenovirus vector-mediated mechanisms. The importance of NK cells for adenovirus-mediated tumor suppression after intratumoral dosing was demonstrated using MDA-MB-231 human breast cancer xenografts in scid (defective T and B cell response) and scid-beige (defective T, B, and NK cell response) mice. There was no adenovirus vector-mediated anti-tumor activity in scid-beige mice. Dexamethasone (Dex) is a potent suppressor of the cellular immune response to recombinant adenovirus in mice and rats. Dex abolished growth suppression caused by adenovirus vector, but did not interfere with the anti-tumor efficacy of p53. Supression of NK cell activity in scid mice using intravenous administration of a neutralizing antibody had the same effect as Dex. These data support a role for NK cells in adenovirus vector-mediated anti-tumor efficacy.

Combination therapy with the farnesyl protein transferase inhibitor SCH66336 and SCH58500 (p53 adenovirus) in preclinical cancer models

SCH66336 is a p.o.-active, farnesyl protein transferase inhibitor. SCH66336 inhibits farnesylation of RAS and other proteins in tumor cells and suppresses tumor growth in human xenograft and transgenic mouse cancer models in vivo. SCH58500 is a replication-deficient, recombinant adenovirus, which expresses the human p53 tumor suppressor. In preclinical models, SCH58500 has therapeutic efficacy against a wide range of human tumor types containing nonfunctional p53 and enhanced activity in combination with many chemotherapeutic drugs. Here we report that combination therapy with SCH66336 and SCH58500 has synergistic or additive antiproliferative effects on a panel of tumor cells lines in vitro. The efficacy of the three-drug combination of SCH66336, SCH58500, and paclitaxel was also examined in vitro. Each two-drug interaction displayed such marked synergy, the addition of a third drug to the statistical model could only yield additivity. Greater combined efficacy for SCH66336 and SCH58500 was also observed in vivo in the DU-145 human prostate and wap-ras/F transgenic mouse cancer models.

The use of laser scanning cytometry to assess depth of penetration of adenovirus p53 gene therapy in human xenograft biopsies

SCH58500 is an agent for gene therapy of cancer, consisting of a replication-deficient type 5 adenovirus (Ad5) expressing the human p53 tumor suppressor gene (Ad5/p53). An important question about the use of Ad5/p53 gene therapy is how to achieve the therapeutically effective delivery of an Ad5/p53 vector to the tumor. We wanted to determine the effective depth of penetration of an Ad5/p53 vector by dosing the vector in an experimental human xenograft/SCID model. To assess depth of penetration, we developed a novel methodology for scanning tissue sections by laser scanning cytometry (LSC). SCID mice were given intraperitoneal injections of either p53(null) SK-OV-3 human ovarian tumor cells or p53(mut) DU-145 human prostate tumor cells to establish xenograft solid tumors. Mice were then dosed once or twice at 24-hour intervals by intraperitoneal injection with SCH58500 (Ad5/p53), an adenovirus construct expressing beta-galactosidase (Ad5/beta-gal), or a buffer control. Additional groups of mice received a single intraperitoneal dose of 10 mg/kg paclitaxel either alone or coadministered with Ad5/p53. Twenty-four hours after each last dose, the human solid tumor xenograft and relevant mouse tissue were removed from each mouse for the analysis of Ad5/p53 penetration. Immunohistochemistry (IHC) for beta-galactosidase protein revealed a depth of penetration of between 1 and 10 cells from the tumor surface. In some mice, hepatocytes in the periportal regions of liver lobules were also positive, indicating systemic absorption of adenovirus from the peritoneal cavity. IHC staining for p53 and p21 proteins in SK-OV-3 solid tumor xenografts revealed similar Ad/p53 penetration. LSC was used to map and quantitate apoptosis in both tumor and liver tissue biopsies, with over 450,000 nuclei from liver tissue and 150,000 nuclei from tumor tissue being evaluated. LSC analysis demonstrated a high level of apoptosis in the tumors that had been removed from Ad5/p53-dosed mice (12.7-19.7%). This level of apoptosis was significantly higher (P < 0.05) than was observed for liver tissues taken from Ad5/p53-dosed mice (2.7-8.0%) or tumor tissues taken from either Ad5/beta-gal-dosed mice (3.0-6.4%) or buffer control-dosed mice (3.0-5.3%). Scan bit maps from the extensive LSC analyses confirmed that apoptosis was present to about the same depth (1-10 cells) as had been identified by IHC for beta-galactosidase, p53, and p21 proteins. Paclitaxel coadministered with Ad5/p53 had no effect on Ad5 penetration into solid tumors in vivo as measured by IHC for p53 or p21 protein. However, the combination therapy did cause an elevation in the number of tumor cells undergoing apoptosis.

A single-chain fusion molecule consisting of peptide, major histocompatibility gene complex class I heavy chain and beta2-microglobulin can fold partially correctly, but binds peptide inefficiently

The function of major histocompatibility complex class I (MHC-I) molecules is to sample peptides from the intracellular environment and present these peptides to CD8+ cytotoxic T lymphocytes (CTL). We have attempted to develop a general approach to produce large amounts of pure and active recombinant MHC-I molecules. A convenient source of MHC-I molecules would be a valuable tool in structural and biochemical analysis of MHC-I, and in experiments using MHC-I molecules to enable specific manipulations of experimental and physiological CTL responses. Here we describe the generation of a recombinant murine MHC-I molecule, which could be produced in large amounts in bacteria. The recombinant MHC-I protein was expressed as a single molecule (PepSc) consisting of the antigenic peptide linked to the MHC-I heavy chain and further linked to human beta2-microglobulin (hbeta2m). The PepSc molecule was denatured, extracted, purified and folded using a recently developed in vitro reiterative refolding strategy. This led to the formation of soluble, recombinant MHC-I molecules, which migrated as monomers of the expected size when submitted to non-reducing sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Serological analysis revealed the presence of some, but not all, MHC-I-specific epitopes. Biochemically, PepSc could bind peptide, however, rather ineffectively. We suggest that a partially correctly refolded MHC-I has been obtained.

Adenovirus-mediated p53 gene therapy has greater efficacy when combined with chemotherapy against human head and neck, ovarian, prostate, and breast cancer

PURPOSE

Adenovirus-mediated p53 gene therapy for cancer is currently undergoing phase I/II clinical trials. The drug used in our clinical trials (p53 Ad; ACN53; SCH58500) consists of a replication-deficient, type 5 adenovirus vector expressing human wildtype p53 tumor suppressor under the control of the cytomegalovirus promoter. In preclinical models, p53 Ad has therapeutic efficacy against a wide range of human tumor types containing nonfunctional p53, both in vitro and in vivo. Results from early clinical trials using p53 gene therapy by itself support optimism for the future of this therapeutic approach. However, it is likely that many phase II/III trials will incorporate an arm comparing traditional chemotherapy against chemotherapy combined with p53 gene therapy. Therefore, it is important to study possible interactions between p53 Ad and chemotherapeutic drugs in preclinical models before starting the clinical trials.

METHODS

Proliferation of tumor cells was quantitated after incubation with various combinations of p53 Ad and chemotherapeutic drugs. Human tumor xenografts in scid mice were dosed with intraperitoneal or intratumoral p53 Ad with or without chemotherapeutic drugs and the tumor burden after therapy monitored.

RESULTS

p53 Ad combined with cisplatin, doxorubicin, 5-fluorouracil, methotrexate, or etoposide inhibited cell proliferation more effectively than chemotherapy alone in SCC-9 head and neck, SCC-15 head and neck, SCC-25 head and neck, SK-OV-3 ovarian, DU-145 prostate, MDA-MB-468 breast, and MDA-MB-231 breast tumor cells. No obvious dependence on dosing schedule was observed. Greater anticancer efficacy was also demonstrated in four human tumor xenograft models in vivo. Of particular significance, there was enhanced efficacy using the three drug combination of p53 Ad, cisplatin, and paclitaxel in an ovarian cancer model.

CONCLUSION

These results support the combination of p53 gene therapy with chemotherapy in clinical trials.

[Physiotherapy as manual therapy]

Manual therapy includes methods where the therapist's hands are used to stretch, mobilize or manipulate the spinal column, paravertebral structures or extremity joints. The aims of these methods are to relieve pain and improve function. In Norway only specially qualified physiotherapists and chiropractors are authorized to perform manipulation of joints (high velocity thrust techniques). To become a qualified manual therapist in Norway one must have a minimum of two years of clinical practice as physiotherapist followed by two year full time postgraduate training in manual therapy (a total of six years). Historically the Norwegian manual therapy system was developed in the 1950s by physiotherapists and medical doctors in England (James Cyriax and James Mennell) and Norway. As a result doctors allowed physiotherapists to use manipulation as a treatment method of both spinal and peripheral joints. In 1957 the Norwegian health authorities introduced reimbursement for manual therapy performed by physiotherapists.

A recombinant adenoviral vector expressing full-length human retinoblastoma susceptibility gene inhibits human tumor cell growth

As a prelude to considering retinoblastoma (RB) gene therapy for cancer, a series of human tumor cell lines with either full-length, mutated, or undetectable RB protein were treated with recombinant adenovirus encoding RB (ACNRB). Both RB protein expression and the cytotoxic and antiproliferative effects of ACNRB treatment were evaluated. While the transgene expression of a reporter virus encoding the beta-galactosidase enzyme (rAd-beta-gal) varied among cell lines, the reintroduction and expression of the RB gene resulted in a pronounced inhibition of cellular proliferation in RB-altered cell lines. An antiproliferative response was observed with control adenovirus treatment in some cell lines. ACNRB treatment did not cause detectable cytotoxicity in either RB+ or RB-altered cells. Dose-dependent cytostasis was observed in RB- cell lines. In vivo tumor suppression was observed in a breast xenograft model subsequent to the treatment of established tumors with ACNRB. These data support a role for RB gene therapy of tumors with RB mutations and provide a basis for the further evaluation of ACNRB gene therapy of human cancer.

Adenovirus-mediated p53 gene therapy and paclitaxel have synergistic efficacy in models of human head and neck, ovarian, prostate, and breast cancer

Synergy (or antagonism) between two chemical agents is an in vitro empirical phenomenon, in which the observed effect of the combination is more (or less) than what would be predicted from the effects of each agent working alone. Although mathematical synergy is not directly provable in the clinical setting, it does predict a favorable outcome when the two therapeutics are combined in vivo and strongly suggests the presence of in vivo synergy. In contrast, overt antagonism warns of future problems. Sophisticated three-dimensional statistical modeling was used to evaluate the presence of synergistic, additive, or antagonistic efficacy between adenovirus (Ad)-mediated p53 gene therapy (p53 Ad) and paclitaxel (Taxol) in a panel of human tumor cell lines. Cells were either pretreated with paclitaxel 24 h before p53 Ad or treated with both agents simultaneously. Cell proliferation was measured 3 days later. Paclitaxel had synergistic or additive efficacy with p53 gene therapy. In no case was the interaction antagonistic. Cell cycle analysis demonstrated that p53 Ad arrested cells in G0/G1 prior to apoptotic cell death, whereas paclitaxel arrested cells in G2-M prior to apoptotic cell death. When combined, the relative concentration of each agent determined the dominant cellular response. These results are consistent with the previously reported cell cycle effects of p53 or paclitaxel, respectively; however, these data fail to explain the observed drug synergy. We found that low concentrations of paclitaxel (1-14 nM) increased the number of cells transduced by recombinant Ad 3-35% in a dose-dependent manner, which is one possible mechanism for the observed synergy. Of particular note, the concentrations of paclitaxel responsible for increased Ad transduction were lower than the concentrations required for microtubule condensation. The efficacy of combination therapy was also evaluated in vivo. In the p53null SK-OV-3 xenograft model of ovarian cancer, a dosing schedule of p53 Ad that, by itself, had a relatively minimal effect on tumor burden (16%) caused a much greater decrease in tumor burden (55%) when combined with paclitaxel. Greater combined efficacy was also observed in the p53mut DU-145 prostate, p53mut MDA-MB-468 breast, and p53mut MDA-MB-231 breast cancer xenograft models in vivo. In summary, p53 Ad for cancer shows enhanced efficacy when combined with paclitaxel. This combination is recommended for clinical cancer trials.

Recombinant E1-deleted adenovirus-mediated gene therapy for cancer: efficacy studies with p53 tumor suppressor gene and liver histology in tumor xenograft models

Type 5 adenoviral (Ad) vectors have been the "vector-of-choice" for preclinical studies on p53 tumor suppressor gene therapy of cancer. Previous studies have examined the in vivo efficacy of p53 Ad when given intratumorally. However published information does little to guide clinicians in the design of intraperitoneal (i.p.) dosing trials for i.p. tumors, e.g., ovarian, or clinical trials using regional organ perfusion, e.g., for lung tumors. Therefore, we examined several parameters with special significance for these routes of administration. Lung metastases from p53mut MDA-MB-231 mammary xenografts were treated with therapeutic levels of intravenous buffer, beta-galactosidase (beta-Gal) Ad, or p53 Ad. Treatment with intravenous p53 Ad significantly reduced the number of metastases per lung and there was a dramatic reduction in the surface area occupied by these tumors as compared to control groups. Two types of i.p. tumor xenografts were used for preclinical modeling of i.p. gene therapy, the p53null SK-OV-3 ovarian and the p53mut DU-145 prostate human cancers. In a study examining the effect of different vehicle volumes on the efficacy of a constant drug dose, all mice treated with p53 Ad had reduced tumor burden compared to controls. Dosing volumes between 0.2 and 1 ml were equally effective and all were more effective than a dosing volume of 0.1 ml. However, reduced efficacy was observed when a volume of 1.5 ml was used. When the effect of dosing frequency on antitumor efficacy was examined, fractionated doses of p53 Ad had somewhat greater efficacy than fewer, bolus injections. One of the significant elements in the emerging toxicology associated with recombinant adenoviruses is the hepatocyte pathology caused by high systemic concentrations of adenovirus. For recombinant Ad used in this study, there was a pronounced dose-dependence for the liver response, with very high, repeated doses causing significant hepatocellular insult. Expression of cytoplasmic beta-Gal protein coincided with areas of greatest damage in mice treated with high doses of beta-Gal Ad. Ultrastructural examination of hepatocyte intranuclear inclusions revealed moderately electron-dense, tightly packed granular material interspersed with more electron-dense nuclear material. Human tumor xenografts, but not mouse tissues, expressed viral hexon protein. In summary, hepatic toxicity caused by high concentrations of recombinant adenovirus was observed in murine cancer models. However, therapeutic levels of p53 Ad could be achieved which had dramatic efficacy without significant pathology.

P53 tumor suppressor gene therapy for cancer

The last two decades have led to a greater understanding of the genetic basis of human malignancy. Although numerous genetic alterations have been detected in cancer, activation of oncogenes and inactivation of cell cycle regulators (e.g., tumor suppressor genes) are now known to play a critical role in the progression of the disease. Therapeutic strategies based on specific molecular alterations in cancer include reintroduction of wild-type tumor suppressor function to cells lacking the gene. p53 gene therapy provides an attractive strategy to test the potential clinical feasibility of this approach. Alterations in p53 function are present in approximately half of all malignancies, and expression of wild-type p53 can result in apoptosis in human tumor cells. This review summarizes current investigations with p53 gene therapy, highlighting the preclinical efforts with adenoviral, retroviral, and lipid-based gene delivery systems. A comprehensive review of the various clinical targets suggested for p53 gene therapy is presented together with challenges and prospects for future clinical investigation.

Efficacy of p53 adenovirus-mediated gene therapy against human breast cancer xenografts

In response to DNA damage, p53 protein accumulates in the cell nucleus causing cells to undergo DNA repair or apoptosis, programmed cell death. Reintroduction of wild-type p53 into tumors with null or mutant p53 offers a novel strategy for controlling tumor growth, by inducing apoptotic death in neoplastic cells. The efficacy of a replication-deficient p53 adenovirus construct was tested against three human breast cancer cell lines expressing mutant p53, MDA-MB-231, -468, and -435. 231 and 468 cells were both highly transduced at a multiplicity of infection of 10. By contrast, 435 cells were rarely transduced. p53 adenovirus-mediated gene therapy was highly effective against 231 and 468 tumor xenografts in nude mice. At a total dose of 2.2 x 10(9) cellular infectious units (CIU), inhibition of 231 tumor growth was 86% (P < or = .01). Thirty-seven percent of that growth inhibition was due to p53, while 49% was adenovirus-specific. Inhibition of 468 tumor growth was 74% (P < or = .001). Forty-five percent of that inhibition was p53-specific, while 28% was adenovirus-specific. The ED50 values for 231 tumors and 468 tumor growth inhibition were 3 x 10(8) CIU and 2 x 10(8) CIU, respectively. Injection of p53 Ad into 231 or 468 tumors induced apoptosis. By contrast, growth inhibition in 435 tumors treated with p53 adenovirus was not significant, probably due to low adenovirus transduction. 231 and 435 cells both expressed high levels of alpha v, beta 1, beta 3, and beta 5 integrin subunits, ruling out lack of the appropriate integrins as the reason for the low infection rate in 435 cells. Our results demonstrate the ability of wild-type p53 to curtail cancerous cell growth in vivo in tumors expressing mutant p53. The ability of beta-gal Ad to infect tumor cells in vitro was generally predictive of in vivo p53 Ad efficacy.

Radiographic detection of cavitation in approximal surfaces of primary teeth using a digital storage phosphor system and conventional film, and the relationship between cavitation and radiographic lesion depth: an in vitro study

The need for operative treatment of approximal carious lesions may depend on whether or not the surface is cavitated. The aims of this in vitro study were to compare the accuracy of cavity detection in approximal surfaces of primary molars using a storage phosphor system (Digora) and Ektaspeed Plus film, and to relate radiographic lesion depth to the presence or absence of cavitation in the tooth surface. The material consisted of 72 approximal surfaces in 46 exfoliated/extracted primary molars. The teeth were radiographed using Ektaspeed Plus film and then the Digora system with 10% of the film exposure dose. Three examiners independently scored the radiographs for the presence or absence of cavitation on a 5-point confidence scale and for lesion depth on a four-category disease severity scale. Validation of the radiographic diagnosis of cavitation was done by inspecting the dried and cleaned surfaces in direct light using a sharp probe. The surfaces were scored: 0 = sound, 1 = discoloration without cavitation, 2 = cavitation. Diagnostic accuracy of the two radiographic methods was evaluated by ROC curve analysis. There was no statistically significant difference between the accuracy of the two methods for detection of cavitation. There was also no significant difference in the proportion of lesions in outer enamel, inner enamel and dentine detected by the two methods. The majority of lesions diagnosed radiographically to be in dentine were cavitated.

Lung carcinoma and malignant mesothelioma in patients exposed to Thorotrast: incidence, histology and p53 status

In a previous registry-based survey of 999 patients injected with alpha-emitting 232ThO2 (Thorotrast), we identified elevated risks for lung carcinoma and malignant mesothelioma. Since injected Thorotrast is retained lifelong mostly in liver, spleen and lymph nodes, the mesothelial surfaces of these organs are constantly irradiated. Thorotrast-administered patients also perpetually exhale 220Rn, a 232Th-daughter. Study of Thorotrast-exposed patients may, therefore, provide data with regard to carcinogenicity of radon exposure, a current public health concern, as well as the pathogenesis of malignant mesothelioma. The incidence and histologic types of lung carcinoma and malignant mesothelioma within the cohort were examined by review of available histopathologic material and medical records. Further, mutations of the p53 gene were analyzed whenever possible as it has previously been suggested that radon-associated lung carcinomas exhibit specific mutational patterns. The cumulative risk for lung carcinoma reached 11.0% based on 20 confirmed cases. Nine were small cell lung cancer (SCLC), whereas the expected frequency was 18%. The risk for malignant mesothelioma reached 2.5% based on 7 cases. The actuarial risk of malignant mesothelioma for patients given more than 20 ml Thorotrast was 7.8% compared to 1.4% for patients administered smaller amounts. Seven lung carcinomas and 5 malignant mesotheliomas were analyzed for p53 mutations; only 1 (in a lung adenocarcinoma) was detected. A possible association between Thorotrast and SCLC is suggested. In addition, a possible dose-response gradient exists for Thorotrast and malignant mesothelioma.

Mutations in the tumor suppressor gene p53 in human liver cancer induced by alpha-particles

The p53 tumor suppressor gene is mutated in varying fractions of almost all tumor types studied. The rate of mutations and the mutational spectrum in some tumors are specific for environmental mutagens assumed to be involved in the carcinogenic process. Thus, hepatocellular carcinomas supposedly induced by aflatoxin exposure often contain a specific point mutation in codon 249, and in lung cancers of miners with heavy radon exposure, another specific point mutation in codon 249 suggestive of an alpha-particle-specific mutation has been shown. The interpretation of studies linking the mutational spectrum with specific environmental exposures is complicated by the multifactorial or unknown genesis of most tumors. However, people given injections of the X-ray contrast medium Thorotrast (Th) in the past have experienced an enormous risk of liver tumors, and virtually all of these are supposedly induced by alpha-particles from the decay of 232Th. The examination of these tumors may provide evidence as to whether specific p53 point mutations are relevant in alpha-particle carcinogenesis. Therefore, we collected paraffin-embedded, formalin-fixed archival tissues from 18 hepatocellular carcinomas, 9 cholangiocarcinomas, and 9 hepatic angiosarcomas from Thorotrast-exposed patients. The tissues were analyzed for p53 protein expression by immunohistochemical staining by using the mAb DO-7 and for mutations of exons 5-8 by PCR and constant denaturant gel electrophoresis. G --> T transversions of the third base of codon 249 of the p53 gene were specifically screened for by restriction enzymes. No high score for p53 protein expression (i.e., positive staining of >20% of examined cells) was observed; lower scores were seen in 5 of 18 (28%) hepatocellular carcinomas, 1 of 9 (11%) cholangiocarcinomas, and 0 of 8 (0%) hepatic angiosarcomas. Only one p53 mutation, a heterozygous T --> G transversion of the first base codon 176, occurred in a hepatocellular carcinoma. The rate of p53 point mutations in alpha-particle-induced liver tumors seems to be lower than in European hepatocellular carcinomas in general. The study does not exclude the possibility that alpha-particle carcinogenesis may involve inactivation of p53 by gross deletions of the gene, but it speaks against the proposed specificity of point mutations of codon 249 in cancer supposedly induced by alpha-particles from radon progeny.

Strategy for developing transgenic assays for screening antineoplastic drugs that affect tubulin polymerization

In this study we evaluated the antitumor efficacy of taxol in four solid tumor models derived from wap-ras line 69 transgenic mice. Taxol inhibited the growth of spontaneous salivary and mammary gland adenocarcinomas in wap-ras mice. In nude mice it was also effective against solid tumors caused by WR21 cells derived from a wap-ras salivary gland tumor. Taxol was not able to prevent tumor emergence in wap-ras/F mice, a subline of the wap-ras strain in which all males develop palpable mammary gland tumors between 1.5 and 3.0 months of age. Our data indicate the range of results that can be expected when this panel of related transgenic tumor models is used to study the antitumor effects of taxol and other therapeutic drugs that act by affecting tubulin polymerization. These models of ras-mediated neoplasia should prove useful for testing anticancer compounds with taxol-like mechanisms of action.

In wap-ras transgenic mice, tumor phenotype but not cyclophosphamide-sensitivity is affected by genetic background

Male wap-ras transgenic mice develop adenocarcinomas in salivary and/or mammary tissue by age 1 year. When the wap-ras transgene was bred into the FVB/N strain, males developed multiple mammary tumors between 1.5 and 3 mo. of age, but no salivary tumors. Crosses between ras/FVB mice and other strains produced moderate changes in mammary tumor onset and severity, but no salivary tumors. Histopathological analysis of 62 adenocarcinomas from 18 mice yielded: 14 tumors with areas of squamous metaplasia, many tumors with epithelium-lined cysts, few immune cells in tumors, and no lung metastases. Cyclophosphamide delayed tumor onset and inhibited the growth of established tumors. Our results suggest that wap-ras mice will be useful for studying ras-mediated tumor genetics and should be a good assay system for both preventative and curative anticancer therapies.

Agents that increase phosphatidic acid inhibit the LH-induced testosterone production

The results of the present study point to phosphatidic acid (PtdOH) as a possible intracellular messenger, which might be involved in local modulation of testicular testosterone production in vivo. Propranolol (27-266 microM) induced an increased level of [3H]PtdOH in isolated rat Leydig cells, prelabeled with [3H]myristate, and at the same time a strong dose-dependent inhibition of the acute testosterone production stimulated by luteinizing hormone (LH). The inhibition was not bypassed by the addition of dibutyryl-cAMP but was overcome, when 22(R)-hydroxycholesterol was added as a direct substrate for cytochrome P-450 side chain cleavage enzyme. Thus, the inhibition appears to be exerted at a point distal to cAMP-generation but before the first enzyme in the testosterone synthetic pathway. Treatment with other agents (4 beta-phorbol 12-myristate 13-acetate (PMA), A23187, and sphingosine) giving rise to increases in the PtdOH-level resulted in the inhibition of the LH-induced testosterone formation as well, thus indicating a connection between the two effects. Furthermore, we were able to demonstrate a highly significant correlation between the PtdOH-increase and the inhibition of the LH-stimulated testosterone production. This may suggest a causal relationship between these two parameters.

Development of a nude mouse model of ras-mediated neoplasia using WR21 cells from a transgenic mouse salivary tumor

A novel cell line (WR21) was derived from a salivary tumor in a male wap-ras transgenic mouse. Salivary tumors in wap-ras transgenic mice are extremely aggressive and express high levels of oncogenic ras protein from the activated, human Ha-ras transgene. WR21 cells also expressed high levels of oncogenic ras protein in vitro and in vivo. They gave rise to aggressive, highly anaplastic solid tumors when injected subcutaneously into athymic nude mice and approximately 90% of the mice had lung metastases by the fifth week of tumor growth. WR21 tumors were inhibited by cyclophosphamide, 5-fluorouracil, adriamycin, mitomycin C and actinomycin D, but not methotrexate. Our results suggest that the WR21/nude mice model will be useful for testing the efficacy of drug therapies against ras-mediated neoplasias.

Evaluation of the wap-ras transgenic mouse as a model system for testing anticancer drugs

Transgenic mouse models have provided many valuable insights into the molecular mechanisms of tumorigenesis; unfortunately, there is a paucity of published information on the utility of these models for evaluating potential anticancer therapeutics. Line 69 wap-ras transgenic mice have an activated, human c-Ha-ras gene on their Y chromosome. Adult males develop salivary and/or mammary adenocarcinomas. Both tumor types express high levels of human ras oncoprotein. Two new sublines, designated wap-ras/F, were created by selective breeding. Subline 69-2 wap-ras/F males developed multiple mammary tumors at puberty. Tumor onset was delayed by cyclophosphamide treatment prior to puberty. Mammary tumors from cyclophosphamide-treated mice weighed 0.57 +/- 0.09 g/mouse (SD +/- SEM; n = 8), while tumors from control mice weighed significantly more at 2.36 +/- 0.25 g/mouse (n = 8; P less than or equal to 0.001; SD +/- SEM). These results suggest that subline 69-2F mice will be valuable for testing therapeutic regimes designed to interfere with processes occurring early in tumorigenesis, before palpable tumor presentation. Tumor sensitivity to several clinically relevant cytotoxins was also tested in adult wap-ras males with palpable tumors. Both salivary and mammary tumors were sensitive to cyclophosphamide and 5-fluorouracil, but not methotrexate. This suggests that wap-ras transgenic mice will indeed be useful in the discovery of novel therapeutics against neoplasia.

Effect of dietary fiber on the disposition and excretion of a food carcinogen (2-14C-labeled MeIQx) in rats

We studied to what extent dietary fiber may affect uptake, retention, and excretion of a food carcinogen (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, MeIQx) occurring in fried meat. Four diets--one fiber-free control and three containing either insoluble dietary fiber isolated from sorghum (100 g/kg) and wheat bran (100 g/kg) or the highly soluble pectin (50 g/kg)--were investigated. The fiber diets were given in amounts of 10 g/day to rats. Thus, each rat received 1 or 0.5 g fiber and 100 micrograms 2-14C-labeled MeIQx uniformly mixed in its daily diet. A 4-day adaptation period with unlabeled MeIQx was followed by a 5-day experimental period with 14C-labeled MeIQx, during which urine and feces were collected separately for analysis of radioactivity and mutagenicity. Furthermore the composition and the fermentability of the dietary fiber were determined. The present study shows that a diet containing fiber, especially fiber isolated from sorghum and wheat bran, affects the excretion pattern of the food carcinogen MeIQx in a manner suggesting a lower uptake and a decreased transit time through the gastrointestinal tract in a more diluted form than a nonfiber diet. Furthermore, less radioactivity was retained in the kidneys with sorghum and wheat bran than with the other two diets. On the other hand, none of these types of dietary fiber affected the retention of the hepatocarcinogen MeIQx in the liver 24 hours after the last oral intake. DNA adducts were formed to a higher extent in the kidney than in the liver. The highest levels were found in animals given the wheat bran diet.

Histopathology of salivary and mammary gland tumors in transgenic mice expressing a human Ha-ras oncogene

Mutated ras genes are powerful transforming agents in vitro and are found in a wide variety of human tumors in vivo. We characterized the histopathology and p21 protein expression associated with tumorigenesis in line 69 transgenic mice carrying an activated, human c-Ha-ras gene on the Y-chromosome (A. C. Andres, C. A. Schonenberger, B. Groner, L. Hennighausen, M. LeMeur, and P. Gerlinger, Proc. Natl. Acad. Sci. USA, 84: 1299-1303, 1987). Male mice developed salivary and/or mammary gland tumors. The salivary tumors were adenosquamous carcinomas arising from serous areas of the submandibular gland. They characteristically exhibited densely packed cords and sheets of moderately anaplastic cells. Tumorigenic tissue had a high mitotic index, and all tumor-bearing animals had an ongoing inflammatory response as evidenced by extensive immune cell infiltration of affected tissue. Half of the mammary gland tumors were adenosquamous carcinomas with multiple foci of squamous metaplasia, while the rest were adenocarcinomas containing glandular tissue. Most tumors had a high mitotic index, and abnormal mitotic figures were common. All tumors produced p21 ras, as confirmed by immunohistochemistry and Western blots. Both tumor types expressed elevated levels of p21 protein. Microscopic lung metastases were present in 5 of 35 animals (14%). Our results suggest that this transgenic mouse will provide a useful model for testing therapies directed against ras-associated tumorigenesis.

Induction of c-fos transcripts in early postimplantation mouse embryos by TGF-alpha, EGF, PDGF, and FGF

The activity of growth factor receptors in the early postimplantation mouse embryo was studied by analyzing changes in expression of mRNA transcripts of an early response gene, c-fos, after binding of specific ligands. Reverse transcription of mRNA coupled with the polymerase chain reaction was used to detect gene transcription in single embryos after exposure to growth factors. Postimplantation embryos (at 7.5 days of gestation) had physiologically active receptors for transforming growth factor-alpha (TGF-alpha), epidermal growth factor (EGF), human platelet-derived growth factor (PDGF), recombinant PDGF-AA homodimer, and basic fibroblast growth factor (FGF), as indicated by induced expression of c-fos mRNA, c-fos expression was not induced in untreated embryos or in embryos incubated with active recombinant PDGF-BB homodimer. These results show that growth factor receptors are functional during early mammalian embryogenesis.

Drosophila alcohol dehydrogenase: a novel reporter gene for use in mammalian embryos

A reporter gene construct containing the Drosophila alcohol dehydrogenase (ADH) gene under regulation of the Rous sarcoma virus long terminal repeat (RSV LTR) was microinjected into mouse zygote pronuclei. ADH activity after injection of the RSV-ADH construct was visualized in cultured embryos by means of a simple histochemical enzyme assay. The RSV LTR was an efficient promoter that led to abundant ADH activity at all stages of preimplantation development. There was a high incidence of mosaicism among stained embryos.

Mineralocorticoid concentrations in unstressed female rabbits and embryonic sodium transport

Plasma aldosterone, corticosterone, and cortisol were measured during the first week of pseudopregnancy or pregnancy in New Zealand White rabbits to determine whether any sustained elevations of adrenal steroids occur. There were no pregnancy-specific alterations in circulating adrenal steroid concentrations during the preimplantation stages of embryonic development. Elevation of plasma aldosterone in vivo did not induce amiloride-sensitive Na+ transport across the embryonic trophectoderm. It therefore seems unlikely that an increase in maternal adrenal steroid concentrations is necessary for the development of amiloride-sensitive Na+ transport in rabbit blastocysts. Sodium efflux from Day 6 post coitum (p.c.) blastocysts was lower than Na+ influx. By day 7 p.c. Na+ efflux was equivalent in magnitude to the component of Na+ influx not inhibited by amiloride. This suggests that between Days 6 and 7 p.c. the amiloride-sensitive component of Na+ influx becomes essential for blastocyst expansion.