Acute stress modulates the outcome of traumatic brain injury-associated gene expression and behavioral responses

Psychological stress and traumatic brain injury (TBI) result in long-lasting emotional and behavioral impairments in patients. So far, the interaction of psychological stress with TBI not only in the brain but also in peripheral organs is poorly understood. Herein, the impact of acute stress (AS) occurring immediately before TBI is investigated. For this, a mouse model of restraint stress and TBI was employed, and their influence on behavior and gene expression in brain regions, the hypothalamic-pituitary-adrenal (HPA) axis, and peripheral organs was analyzed. Results demonstrate that, compared to single AS or TBI exposure, mice treated with AS prior to TBI showed sex-specific alterations in body weight, memory function, and locomotion. The induction of immediate early genes (IEGs, e.g., c-Fos) by TBI was modulated by previous AS in several brain regions. Furthermore, IEG upregulation along the HPA axis (e.g., pituitary, adrenal glands) and other peripheral organs (e.g., heart) was modulated by AS-TBI interaction. Proteomics of plasma samples revealed proteins potentially mediating this interaction. Finally, the deletion of Atf3 diminished the TBI-induced induction of IEGs in peripheral organs but left them largely unaltered in the brain. In summary, AS immediately before brain injury affects the brain and, to a strong degree, also responses in peripheral organs.

An open-label, multicenter, phase I/II study of AT-101 in combination with docetaxel (D) and prednisone (P) in men with castrate-resistant prostate cancer (CRPC)

5062

Background: Antiapoptotic Bcl-2 family proteins are overexpressed in CRPC and contribute to resistance to therapy. The oral pan-Bcl-2 inhibitor AT-101 (Bcl-2, Bcl-XL, Bcl-W, Mcl-1) is active as a single agent and in combination in in vitro and in vivo tumor models and as a single agent in CRPC. The Phase 1 portion of the study determined the recommended dose for phase II to be D (75mg/m2 q3weeks) in combination with P (5mg b.i.d. on days 1–21), and AT-101 at 40mg b.i.d. on days 1–3 of each 21-day cycle, and was previously reported. Methods: Men ≥18 years of age with chemotherapy-naïve CRPC (N = 36). Safety (NCI CTCAE v3.0) and efficacy (Bubley Criteria for PSA) were assessed at 3-wk intervals. Radiological assessments were performed at 6-wk intervals for pts with soft tissue disease and bone scans were performed after cycle 6 and at the completion of therapy. Results: 36 patients (pts) have been enrolled in the study. Twenty-four (67%) pts achieved a partial response (PR) (>50% PSA decline), and 26 (72%) pts treated had at least a 30% decrease in PSA level. Nine of 19 pts (47%) with measurable disease had a PR. One PR was unconfirmed per RECIST. Thirteen pts (36%) completed >10 cycles of therapy (range 2–24) thus far. Four pts remains active. Safety data is available for 31 pts. The most common (>20%) Adverse Events (AEs) include: fatigue (68%), nausea (52%), diarrhea (45%), alopecia (32%), constipation and dysgeusia (26%), and neutropenia and vomiting (26%). Neutropenia was the only gr. 4 event occurring in more than one pt (3pts). Serious Adverse Events (SAEs) considered related were reported in 5 pts (16%). The only SAEs reported in 2 or more pts were urinary tract infection (3 pts) and deep vein thrombosis (2 pts) and none were considered related. No ileus has been reported. Conclusions: AT-101 when given in combination with D/P is well tolerated and shows preliminary evidence of efficacy in pts with CRPC. A randomized trial is ongoing.

[Table: see text]

Analysis of a phase I pharmacokinetic (PK)/food effect study of AT-101 in patients with advanced solid tumors

2557

Background: AT-101 is an oral, pan-Bcl-2 inhibitor (Bcl-2, Bcl-XL, Bcl-W, Mcl-1). Overexpression of Bcl-2 family proteins is common in human cancers. AT-101 activity as a single agent as well as in combination with docetaxel has been reported. The ongoing Phase 1 study of AT-101 as a single agent was expanded to include a cohort of patients to determine the PK of AT-101 in fed and fasted states. Methods: Twelve patients (pts) were enrolled and randomized into cohorts of six pts each. Cohort A received AT-101 (80 mg) orally on day 1 on an empty stomach (fasted) and again on day 8 with a high fat high calorie breakfast (fed), per FDA guidelines. Cohort B received AT-101 on day 1 fed and on day 8 fasted. Preliminary plasma concentration time data for AT-101 from 10 patients administered 80 mg orally were evaluated using noncompartmental analysis. Log transformed peak concentration (Cmax) and exposure (AUC) were compared the between fed and fasted groups with the fasted group as the reference treatment. Results: Preliminary PK results from the first 10 pts are shown in the Table. For AUC and Cmax, the effect of food resulted in an approximately 42% and 5% increase, respectively. However the confidence intervals were not wholly outside the 80–125% intervals. Conclusions: These data indicate that food may increase AT-101 exposure in terms of AUC and Cmax. Updated results from all 12 pts will be presented at the meeting. Based on our preliminary results, it is recommended that AT-101 be taken at least an hour (or more) before or after food.

[Table: see text]

[Table: see text]

AT-101 or placebo (P) with docetaxel (D) in second-line NSCLC with gene signature biomarker development

3577

Background: AT-101 inhibits the Bcl-2 protein family (Bcl-2, Bcl-xL, Mcl-1, Bcl-W) with broad preclinical activity including synergy with D. Methods: We conducted a randomized, double-blind, P-controlled phase 2 study. Patients had received 1 prior chemotherapy regimen for advanced NSCLC. Patients received AT-101 (40 mg b.i.d. days 1–3) or P with D (75 mg/m2 day 1) Q 21 days. Primary endpoint was progression-free survival (PFS) by independent review (IR). Secondary endpoints were overall survival (OS) and investigator determined PFS. 102 patients were planned for 70 events (80% power, HR 0.6, 1-sided alpha 0.1). A biomarker of AT-101 activity was developed by treating 55 NSCLC cell lines with AT-101 and using the corresponding gene expression data to identify a genomic predictor of sensitivity to AT-101. Results: 106 patients were randomized. Baseline factors were balanced. Median OS for patients on AT-101+D was 7.3 months versus 5.6 months for P + D arm (HR 0.60, p = 0.05). The median investigator determined PFS was 12.6 weeks and 10.7 weeks for AT-101+D and P+D arms respectively (HR 1.0, p = 0.49); IR is ongoing. Common adverse events were fatigue (18%), anemia (18%), and dyspnea (18%). Grade 1/2 headaches occurred more frequently in the AT-101 arm. Analysis of gene expression data by Bayesian regression revealed a robust 500 gene predictor of sensitivity to AT-101 that was cross validated in a leave one out analysis and in an independent cohort of 32 NSCLC cell lines. Validation of the predictor in patient samples from the trial is ongoing. Conclusions: In this phase II trial AT-101, an oral pan Bcl-2 family inhibitor, had favorable OS compared to placebo when combined with docetaxel in previously treated NSCLC and was well tolerated. A genomic predictor of AT-101 sensitivity is likely to enrich for responders and identify novel therapeutic combinations for future

[Table: see text]

Small molecule pan-bcl-2 inhibitor AT-101 induces apoptosis in NSCLC by up-regulating noxa and enhances antitumor activity of docetaxel or targeted kinase inhibitors

e14591

Background: AT-101 is an orally active pan Bcl-2 inhibitor currently under clinical development in Phase II trials. We investigated the effect of AT-101 alone or in combination with chemotherapies or targeted kinase inhibitors in NSCLC both in vitro and in vivo. Methods: Growth inhibition was measured by WST assays. The CalculSyn method was used to assess drug interaction by calculating the Combination Index (CI) value. The ability of AT-101 to potentiate the anti-cancer effect of chemotherapies or kinase inhibitors was evaluated in xenograft models. Results: A panel of 11 NSCLC cell lines with overexpression of Bcl-2, Bcl- XL or Mcl-1 proteins was treated with AT-101, docetaxel, pemetrexed, erlotinib, sorafenib, sunitinib, rapamycin, as a single agent and in combination. AT-101 inhibited the growth with IC50 at 3–9 uM. When treating cells simultaneously with both agents, AT-101 demonstrated strong synergy with those agents in A549 or H460 cells with CI values < 1.0. Protein analysis results indicated that AT-101 caused apoptosis by a time- and dose-dependent induction of Noxa expression in those cells. The expression of Bcl- XL was not influenced by AT-101. Pro-Caspase-3 was reduced with increasing doses of AT-101. In vivo, combined treatment of AT-101 with docetaxel, erlotinib, or sorafenib synergistically suppressed subcutaneous NSCLC A549 cells tumor growth compared with treatment with either agent alone. The synergist effects with the ErbB1 inhibitor Erlotinib is associated with the overexpression of the target protein ErbB1 in those cells. Only combination therapy resulted in significant tumor growth delay and no significant toxicities were observed. Conclusions: Our results demonstrate that AT-101significantly enhances the anti-tumor activity of chemotherapy and targeted agents and may represent a promising new anticancer agent with a novel molecular mechanism. Molecular targeted therapy with AT-101 may improve the outcome of current chemotherapy for NSCLC with Bcl-2, Bcl-xL and/or Mcl-1 overexpression.

[Table: see text]

A phase I/II (P1/P2) study of AT-101 in combination with topotecan (T) in patients with relapsed or refractory small cell lung cancer (SCLC) after prior platinum-containing first-line chemotherapy

8106

Background: Bcl-2 family proteins are expressed in SCLC and are associated with chemotherapy resistance. AT-101 is an oral, pan Bcl-2 family protein inhibitor (Bcl-2, Bcl-XL, Mcl-1, and Bcl-w) and potent inducer of proapoptotic proteins. AT-101 has demonstrated activity in SCLC models, including those that express Mcl-1 and are resistant to other Bcl-2 inhibitors. The P1 portion of the study was previously reported. Methods: Pts ≥18 years of age, PS 0–1, with relapsed or refractory SCLC after first line chemotherapy with measurable disease per RECIST were eligible. Pts were stratified into 2 cohorts; cohort A ≥ 60 days and cohort B < 60 days relapse from prior chemotherapy and treated with T 1.25 mg/m2 daily and AT-101 40 mgs daily on days 1–5, q21 along with the use of myeloid growth factors. Adverse Events (AEs) were graded by the NCI CTCAE v. 3.0. Efficacy assessments (RECIST) were performed every 6-weeks. A 2-stage design was used with power/alpha of 80%/0.05 to detect a RR of > 25% and > 5%, in cohort A and B respectively. Results: 36 pts enrolled: ages 41–76; cohort A/B 23/13. The PR/SD/PD/NE rates were 17%/70%/9%/4% and 8%/54%/23%/15%, in cohorts A/B respectively. The median times to progression (TTP) were 18 and 13 weeks, respectively. The most common (>20 %) AEs (all grades): anemia (64%); neutropenia (53%); nausea (47%); fatigue (44%); thrombocytopenia (42%); dyspnoea (25%); and vomiting (22%). Most common Grade 3/4 related events (>5%): neutropenia (31%); thrombocytopenia (25%); anemia (14%); and asthenia (6%). No ileus was reported. Conclusions: AT-101 can be safely combined with T. The observed toxicities were consistent with the known rates of G4 cytopenias of T alone. The response rates observed did not meet the criteria for additional enrolment; however, many patients had a best response of SD and the median TTP in both cohorts was favorable compared to historical controls. Additional trials of AT-101 in SCLC are ongoing.

[Table: see text]

Extended phase I trial of the oral pan-Bcl-2 inhibitor AT-101 by multiple dosing schedules in patients with advanced cancers

e14537

Background: Over-expression of Bcl-2 family proteins is common in human cancers. Initial trials of the oral, pan-Bcl-2 inhibitor AT-101 showed acute dose limiting toxicity of Gr 3–4 AST/ALT (MTD 40 mg/d) and ileus with prolonged dosing daily (QD) for 21/28 days per cycle (Saleh, NCI/EORTC, 2005; James, ASCO, 2006 and Saleh, ASCO, 2007). MTD in the QD schedule has been previously reported. In this study different dosing schedules of AT-101 were tested in adults with advanced cancers and final results for the pulse dosing schedule of twice a day for three days every other week (b.i.d. x 3d EOW) are being reported. Methods: Serial patient (pt) cohorts received AT-101 at escalating doses of 30–80 mg b.i.d. x 3d EOW. Adverse events (AEs) were graded by the NCI CTCAE v3.0. Efficacy was determined by RECIST. Results: 37 pts have been enrolled. Safety data is available on 34/37 pts. In this b.i.d. x 3d EOW dosing schedule, ileus/small bowel obstruction (SBO) occurred in 3 pts (one at each dose level of 30, 40 and 50 mg) and was the dose limiting toxicity for this schedule. Of note, the SBO that occurred at 30 mg was felt to be unrelated to study agent therefore, 30 mg b.i.d. x 3d EOW was the MTD determined for this schedule. The most common (>50%) grade 1–2 AEs included: nausea, vomiting, diarrhea, fatigue and anorexia. Grade 3–4 AEs occurring in > 2 pts include: nausea, abdominal pain, elevated AST (3 pts each), vomiting, fatigue, dehydration (4 pts each), hypokalemia (5 pts). Stable disease was reported in 13/37 (35%) pts. One pt with NSCLC continues on study with stable disease for 33 cycles and 2 additional pts were on study with stable disease for 18 and 9 cycles. The mean Plasma Cmax was 301 ng/ml (+ 477 ng/ml SD) and mean AUC for 30 mg b.i.d.x3d EOW was 1080 ng*hr/ml (+ 1990 ng/ml SD) with a median peak concentration at 4 hours post dose. Conclusions: Pulse dosing of AT-101 achieved an MTD of 30mg b.i.d. x 3d EOW and is associated with reduced toxicity than continuous daily dosing, and may be preferable in combination regimens.

[Table: see text]

An open-label, multicenter, phase II study of AT-101 in combination with rituximab (R) in patients with untreated, grade 1-2, follicular non-Hodgkin's lymphoma (FL)

8582

Background: Bcl-2 family proteins are overexpressed in the majority of patients with FL and contribute to resistance to therapy. AT-101 is a pan-Bcl-2 inhibitor (Bcl-2, Bcl-XL, Bcl-W, and Mcl-1) and potent inducer of proapoptotic proteins. It is active as a single agent and in combination with R in NHL tumor models. Methods: Patients with untreated FL who did not require immediate chemotherapy were eligible. Treatment consisted of an induction cycle of AT-101 (30mg po daily × 21) and R (375 mg/m2 weekly × 4) followed by up to 4 maintenance cycles of AT-101 (30mg po daily × 21) and R (375 mg/m2) every 8 weeks in nonprogressors. Endpoints evaluated the response rate (RR) at week 8 (primary), overall response rate (ORR), molecular response rate (BCL-2JH rearrangement in blood and bone marrow), and safety of the combination. A mini-Max, 2-stage design (52 pts planned) was used to detect >70% RR with power of 90% and alpha of 0.10. Results: 23 pts enrolled: median age 64 yrs; FLIPI 0–5: 0%/17%/65%/13%/4%; Grade 1/2: 61%/39%; bulky disease (>5cm3): 35%; stage: 1–4 4%/4%/30%/61%; bone marrow + 48%. All pts received induction and 18 pts received 1 or more maintenance cycles. RR following induction was 26% (95%CI=10.2–48.4), 4% CR and the best ORR was 70% (95%CI=47.1–86.8), 35% CR. Molecular response analysis is ongoing. Grade 3/4 AEs that occurred in ≥2 pts: nausea 4(17%), vomiting 2(9%), abdominal pain 2(9%), fatigue 2(9%), and small bowel obstruction 2(9%). AT-101 was reduced to 20mg daily x 21 which improved GI tolerability. Conclusions: The combination of AT-101 and R was well tolerated. The week 8 RR did not meet statistical criteria to enroll stage II. The best ORR is at the upper limit of reported ORR for R alone; therefore a randomized trial is required to definitively determine activity of the combination.

[Table: see text]

Preliminary report of an open-label, multicenter, phase I/II study of AT-101 in combination with docetaxel (D) and prednisone (P) in men with docetaxel refractory prostate cancer

5145

Background: Antiapoptotic Bcl-2 family proteins are overexpressed in castrate resistant prostate cancer (CRPC) and contribute to resistance to therapy. AT-101 is a pan-Bcl-2 inhibitor (Bcl-2, Bcl-XL, Bcl-W, and Mcl-1) and potent inducer of proapoptotic proteins. AT-101 is active as a single agent and in combinations with standard therapies in in vitro and in vivo tumor models, as a single agent in a phase II trial in CRPC, and in combination with D/P as first-line therapy in CRPC, as demonstrated by declines in PSA and RECIST responses. Methods: Men ≥18 years of age with docetaxel-refractory CRPC were eligible. Patients (pts) must have PSA progression per the Bubley criteria or documented disease progression while receiving prior D/P therapy. Pts (n = 40) were treated with D (75 mg/m2 day 1), P (5mg b.i.d. on days 1–21) and AT-101 40mg b.i.d. on days 1–3 of each 21-day cycle. Safety (NCI CTCAE v3.0) and efficacy (Bubley Criteria for PSA) were assessed at 3-wk intervals. Radiological assessments were performed at 6-wk intervals for pts with soft tissue disease and bone scans were performed after cycle 6 and at the completion of therapy. Results: Efficacy data was available on 34 pts. Thirty-five percent (12/34) of pts treated had at least a 30% decrease in PSA level and 18% (6/34) of pts achieved a >50% PSA decline. Twenty one of 34 pts included in this analysis had measurable disease. Five pts (24%) with measurable disease had a PR or CR by RECIST criteria and one additional patient had tumor shrinkage of 29%. Two (2) RECIST PRs are unconfirmed. Thus far, 3 pts have been on therapy for 6 months or more and 15 pts remain on study. Safety data was available on 22 pts. The most common (>20%) adverse events (AEs) included fatigue (55%), anorexia, including weight decreased (45%), diarrhea and nausea (27%), vomiting and neutropenia (23%). The grade 3/4 AEs occurring in more than 1 pt were: neutropenia (5), anemia, anorexia, dyspnea and leukopenia (2 pts each). One partial small bowel obstruction was the only related, serious adverse event (SAE) reported to date. Conclusions: This data supports that AT-101 can be administered safely with D/P in pts with CRPC who are docetaxel-refractory. Durable PSA and RECIST responses were observed.

[Table: see text]

Targeting the human double minute (HDM)-2 ubiquitin ligase as a strategy against non-Hodgkin’s lymphoma

14016

Background: The ubiquitin-proteasome pathway has been validated as a target for non-Hodgkin lymphoma (NHL) with the recent approval of bortezomib for mantle cell lymphoma (MCL). In addition to anti-tumor activity, however, proteasome inhibitors have pleiotropic effects, including activation of an anti-apoptotic heat shock protein response, and their use clinically is complicated by toxicities such as peripheral neuropathy. By targeting E3 ubiquitin ligases, which are involved in ubiquitination of only a small subset of cellular proteins, it may be possible to achieve more specific anti-tumor effects with a better therapeutic index. One attractive target is HDM-2, which is responsible for ubiquitination of the p53 tumor suppressor. Methods: To evaluate the therapeutic potential of agents targeting HDM-2, we studied the impact of the small molecule MI-63, an inhibitor of the HDM-2-p53 interaction, in both p53 wild-type and -mutant cell line models. Results: Treatment of wild-type p53 MCL, NHL, and acute lymphocytic leukemia (ALL) cell lines with MI-63 induced a dose- and time- dependent inhibition of proliferation, with an IC50 in the 1.0–5.0 μM range. This was associated with G1/S cell cycle arrest , and apoptosis mediated by caspase-3. MI-63 induced accumulation and phopshorylation of p53 and also enhanced MDM-2 levels. Multiple p53 target genes were induced, including p21Cip1 and p53-upregulated modulator of apoptosis (PUMA), resulting in cleavage of poly-ADP-ribose-polymerase (PARP). Cell lines expressing certain p53 mutants were sensitive to the effects of MI-63, resulting in activation of caspases 3, 8, 9 and apoptosis. Cells without p53 expression were resistant to MI-63, but at higher drug concentrations proliferation was still inhibited, indicating a possible impact on HDM-2-mediated but p53-independent cell death pathways. Combinations of MI-63 with other anti-tumor agents showed enhanced anti-proliferative effects that met the criteria for synergistic interactions. Conclusions: Inhibition of the HDM-2-p53 interaction is a promising approach both by itself, and in combination with currently used chemotherapeutics, against lymphoid malignancies, providing a rational for translation of this agent into the clinic.

No significant financial relationships to disclose.

Random aneuploidy in CML patients at diagnosis and under imatinib treatment

Chronic myeloid leukemia (CML) is characterized by the presence of a BCR-ABL fusion gene, which is the result of a reciprocal translocation between chromosomes 9 and 22, and is cytogenetically visible as a shortened chromosome 22 (Philadelphia). Research during the past two decades has established that BCR-ABL is probably the pathogenetic pathway leading to CML, and that constitutive tyrosine kinase activity is central to BCR-ABL capacity to transform hematopoietic cells in vitro and in vivo. The tyrosine kinase inhibitor imatinib mesylate was introduced into the treatment regimen for CML in 1998. During the last few years, reports on chromosomal changes during imatinib treatment have been described. In this study, we evaluated the random aneuploidy rate with chromosomes 9 and 18 in bone marrow from treated and untreated patients. We found higher aneuploidy rates in both treated and untreated patients compared to the control group. In three patients who were treated with imatinib mesylate for more than 1.5 years, triploidy also appeared in some nuclei. To our knowledge, this is the first report on new chromosomal changes such as random aneuploidy and triploidy under imatinib treatment, but more studies are needed to investigate the long-term effect of the imatinib treatment on genetic instability.

The influence of different chromosomal aberrations on molecular cytogenetic parameters in chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia of adults in Western countries. The most frequent recurring chromosomal aberrations identified in B-CLL patients are trisomy 12 and deletions of 13q, 17p, and 11q. Cases with deletions of 11q and 17p have a poor prognosis, whereas cases with deletions in 13q have a favorable prognosis. It was previously shown that CLL patients with trisomy 12 and del(13)(q14) have a higher rate of asynchronous replication of normal structural genes when compared to those with normal karyotypes. We studied the replication pattern of the structural locus 21q22 and the imprinted gene SNRPN and its telomere (15qter) and the random aneuploidy of chromosomes 9 and 18 in CLL patients with trisomy 12 and deletions of 11q and 17p, and compared the results to those of CLL patients without these aberrations and to healthy controls. Random aneuploidy rate was higher in the group of patients with trisomy 12 as compared to all other groups. The replication pattern with higher asynchronous pattern was found in both aberration groups compared to the CLL patients without the aberrations and to the control group with involvement of 21q22 and 15qter, whereas the highest synchronous group was found in the 2 aberrations CLL patient groups compared to the other groups with the imprinted locus SNRPN. The existence and significance of chromosomal aberrations in CLL have a deleterious effect on the processes of cell cycle and gene replication and may have biological and prognostic implications.

Adsorption of 6-mercaptopurine and 6-mercaptopurine-ribosideon silver colloid: A pH-dependent surface-enhanced Raman spectroscopy and density functional theory study. II. 6-mercaptopurine-riboside

Surface-enhanced Raman spectroscopy (SERS) has been applied to characterize the interaction of 6-mercaptopurine-ribose (6MPR), an active drug used in chemotherapy of acute lymphoblastic leukemia, with a model biological substrate at therapeutic concentrations and as function of the pH value. Therefore, a detailed vibrational analysis of crystalline and solvated (6MPR) based on Density Functional Theory (DFT) calculations of the thion and thiol tautomers has been performed. 6MPR adopts the thion tautomeric form in the polycrystalline state. The SERS spectra of 6MPR and 6-mercaptopurine (6MP) recorded on silver colloid provided evidence that the ribose derivative shows different adsorption behavior compared with the free base. Under acidic conditions, the adsorption of 6MPR on the metal surface via the N7 and possibly S atoms was proposed to have a perpendicular orientation, while 6MP is probably adsorbed through the N9 and N3 atoms. Under basic conditions both molecules are adsorbed through the N1 and possibly S atoms, but 6MP has a more tilted orientation on the silver colloidal surface while 6MPR adopts a perpendicular orientation. The reorientation of the 6MPR molecule on the surface starts at pH 8 while in the case of 6MP the reorientation starts around pH 6. Under basic conditions, the presence of the anionic molecular species for both molecules is suggested. The deprotonation of 6MP is completed at pH 8 while the deprotonation of the riboside is finished at pH 10. For low drug concentrations under neutral conditions and for pH values 8 and 9, 6MPR interacts with the substrate through both N7 and N1 atoms, possibly forming two differently adsorbed species, while for 6MP only one species adsorbed via N1 was evidenced.

Positional cloning of the mouse obese gene and its human homologue

The mechanisms that balance food intake and energy expenditure determine who will be obese and who will be lean. One of the molecules that regulates energy balance in the mouse is the obese (ob) gene. Mutation of ob results in profound obesity and type II diabetes as part of a syndrome that resembles morbid obesity in humans. The ob gene product may function as part of a signalling pathway from adipose tissue that acts to regulate the size of the body fat depot.

Microdissection of proximal mouse chromosome 6: identification of RFLPs tightly linked to the ob mutation

In a previous report, the ob mutation was mapped to a position 5 cM distal to Met on murine Chromosome (Chr) 6 in tight linkage to Cpa. In order to identify additional RFLPs in the region of ob, we have made use of chromosome microdissection of a 6:16 Robertsonian chromosome. In total, 19 RFLPs were used to type 131 progency of a B6D2 ob/ + x B6 spretus ob/ + intercross. Fifteen of the RFLPs mapped to Chr 6, one of which, D6Rck13, was tightly linked to ob. For refinement of the genetic map around ob, 350 obese progency of a B6 Mus castaneus ob/ + intercross were characterized. DNAs from these animals were typed for microsatellite markers from Chr 6 that flank ob. Recombinants were then typed for D6Rck13. D6Rck13 was nonrecombinant among all the progency of both crosses corresponding to 831 meioses. This probe will be of use as an entry point for physical mapping of the ob mutation.