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Biomedical subjects

Jennifer A Chan

Publications and source records attributed to Jennifer A Chan.

12 recordsLinked to original sources
PubMed2026

Cabozantinib for advanced grade 3 neuroendocrine tumors: subgroup analysis of the phase 3 CABINET trial (Alliance A021602).

Well-differentiated grade 3 neuroendocrine tumors (NETs) have recently been described as a distinct category, and randomized data regarding efficacy of therapy for these patients are scarce. In the phase 3 CABINET trial, cabozantinib improved PFS compared with placebo in patients with advanced, previously treated, progressive extra-pancreatic NETs (epNETs) and pancreatic NETs (pNETs) of all grades. Here, we evaluate if these results remain consistent in a subgroup of patients with well-differentiated G3 NETs. Patients with locally advanced or metastatic epNETs or pNETs were randomized 2:1 in independent cohorts to receive cabozantinib 60 mg daily vs placebo. We analyzed outcomes of the subset of patients with G3 NETs (Ki-67 > 20%), combining patients in the pNET and epNET cohorts due to small sample sizes. Twenty-four patients had G3 NETs, 16 randomized to cabozantinib and 8 to placebo. Primary sites included pancreas (n = 12), GI tract (n = 7), unknown primary sites (n = 3), and lung/thymus (n = 2). Median PFS for patients with G3 NETs treated with cabozantinib was 7.9 vs 3 months with placebo (HR = 0.15, 95% CI: 0.04-0.57, 1-sided log-rank P = 0.0034). The confirmed overall radiographic response rate was 25% (4/16) with cabozantinib vs 0% (0/8) with placebo. Safety outcomes were consistent with published data for the trial as a whole. Subset analysis of the CABINET trial showed improved PFS associated with cabozantinib vs placebo for G3 NETs of pancreatic and extra-pancreatic origin. Despite limited numbers, these results suggest that cabozantinib can be an effective option for patients with advanced G3 NETs. ClinicalTrials.gov Identifier: NCT03375320.

Humans↗
PubMed2006

Hormone replacement therapy and survival after colorectal cancer diagnosis.

PURPOSE: Postmenopausal estrogen use has been shown to decrease the incidence of colorectal cancer, but there is limited information regarding the effect of estrogen use on survival after diagnosis of colorectal cancer. PARTICIPANTS AND METHODS: We examined the influence of postmenopausal estrogen use on mortality among 834 women participating in the Nurses' Health Study who were diagnosed with colorectal cancer between 1976 and 2000 and observed until death or June 2004, whichever came first. Colorectal cancer-specific mortality and overall mortality according to categories of hormone use were assessed. Cox proportional hazards models were used to calculate hazard ratios (HRs) adjusted for other risk factors for cancer survival. RESULTS: Postmenopausal estrogen use before diagnosis of colorectal cancer was associated with significant reduction in mortality. Compared with women with no prior estrogen use, those reporting current use before diagnosis had an adjusted HR of 0.64 (95% CI, 0.47 to 0.88) for colorectal cancer-specific mortality and 0.74 (95% CI, 0.56 to 0.97) for overall mortality. This inverse association between hormone use and mortality was most evident among women whose duration of use was less than 5 years. Longer durations and past use were not associated with significant survival benefit. Assessment of estrogen use after diagnosis demonstrated similar findings. CONCLUSION: Current postmenopausal estrogen use before diagnosis of colorectal cancer was associated with improved colorectal cancer-specific and overall mortality. This benefit was principally limited to women who initiated estrogens within 5 years of diagnosis. Additional efforts to understand mechanisms through which estrogens influence colorectal carcinogenesis and cancer progression seem warranted.

Aged↗
PubMed2006

CXCR4 inhibition synergizes with cytotoxic chemotherapy in gliomas.

PURPOSE: The chemokine receptor CXCR4 is expressed in many different cancers. In malignant brain tumors, CXCR4 signaling has been implicated in tumor growth, survival, and migration, and pharmacologic inhibition of CXCR4 results in decreased tumor growth in preclinical models. To understand how CXCR4 inhibitors may be incorporated into clinical therapy, we examined determinants of responsiveness to CXCR4 inhibition. Because optimal use of CXCR4 inhibition will likely be a part of multimodality therapy, we also investigated the efficacy of CXCR4 inhibition combined with conventional cytotoxic chemotherapy. EXPERIMENTAL DESIGN: CXCR4 protein levels and responsiveness to the CXCR4 inhibitor AMD3100 were determined in a panel of glioblastoma multiforme cell lines. The effects of AMD3100, alone or in combination with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), on cell growth were determined for several of these cell lines in vitro. We used an orthotopic model of glioblastoma multiforme to evaluate the antitumor efficacy of AMD3100 combined with BCNU in vivo. RESULTS: The level of CXCR4 protein expression in glioblastoma multiforme cells predicts the dose at which there is a response to AMD3100; cells that express higher levels of CXCR4 protein require higher doses for equivalent response. In all cell lines tested, treatment of glioblastoma multiforme cells with BCNU followed by AMD3100 results in synergistic antitumor efficacy in vitro. This synergy can also be seen in an orthotopic glioblastoma multiforme model. Treatment with subtherapeutic doses of BCNU in combination with AMD3100 results in tumor regression in vivo, and this reflects both increased apoptosis and decreased proliferation following combination therapy. CONCLUSION: These studies support testing CXCR4 inhibitors in patients with glioblastoma multiforme and establish that inhibition of CXCR4 synergizes with conventional cytotoxic therapies in a clinically relevant combinatorial strategy.

Animals↗
PubMed2006

Physical activity and survival after colorectal cancer diagnosis.

PURPOSE: Physically active individuals have a lower risk of developing colorectal cancer but the influence of exercise on cancer survival is unknown. PATIENTS AND METHODS: By a prospective, observational study of 573 women with stage I to III colorectal cancer, we studied colorectal cancer-specific and overall mortality according to predefined physical activity categories before and after diagnosis and by change in activity after diagnosis. To minimize bias by occult recurrences, we excluded women who died within 6 months of their postdiagnosis physical activity assessment. RESULTS: Increasing levels of exercise after diagnosis of nonmetastatic colorectal cancer reduced cancer-specific mortality (P for trend = .008) and overall mortality (P for trend = .003). Compared with women who engaged in less than 3 metabolic equivalent task [MET] -hours per week of physical activity, those engaging in at least 18 MET-hours per week had an adjusted hazard ratio for colorectal cancer-specific mortality of 0.39 (95% CI, 0.18 to 0.82) and an adjusted hazard ratio for overall mortality of 0.43 (95% CI, 0.25 to 0.74). These results remained unchanged even after excluding women who died within 12 and 24 months of activity assessment. Prediagnosis physical activity was not predictive of mortality. Women who increased their activity (when comparing prediagnosis to postdiagnosis values) had a hazard ratio of 0.48 (95% CI, 0.24 to 0.97) for colorectal cancer deaths and a hazard ratio of 0.51 (95% CI, 0.30 to 0.85) for any-cause death, compared with those with no change in activity. CONCLUSION: Recreational physical activity after the diagnosis of stages I to III colorectal cancer may reduce the risk of colorectal cancer-specific and overall mortality.

Aged↗
PubMed2005

Migration from a mitogenic niche promotes cell-cycle exit.

During development, neural precursors proliferate in one location and migrate to the residence of their mature function. The transition from a proliferative stage to a migratory stage is a critical juncture; errors in this process may result in tumor formation, mental retardation, or epilepsy. This transition could be the result of a simple sequential process in which precursors exit the cell cycle and then begin to migrate or a dynamically regulated process in which migration away from a mitogenic niche induces precursors to exit the cell cycle. Here, we show, using in vivo and in vitro approaches, that granule cell precursors proliferate when they are exposed to the microenvironment of the external granule cell layer (EGL) and exit the cell cycle as a result of migrating away from this environment. In vivo, granule cell precursors that remain in the EGL because of impaired migration continue to proliferate in the mitogenic niche of the EGL. In vitro, granule cell precursors that are introduced into an organotypic cerebellar slice proliferate preferentially in the EGL. We identify Sonic Hedgehog as a critical component of the EGL mitogenic niche. Together, these data indicate that migration away from a mitogenic niche promotes transition from a proliferative to a nonproliferative, migratory stage.

Animals↗
PubMed2005

Antibodies from inflamed central nervous system tissue recognize myelin oligodendrocyte glycoprotein.

Autoantibodies to myelin oligodendrocyte glycoprotein (MOG) can induce demyelination and oligodendrocyte loss in models of multiple sclerosis (MS). Whether anti-MOG Abs play a similar role in patients with MS or inflammatory CNS diseases by epitope spreading is unclear. We have therefore examined whether autoantibodies that bind properly folded MOG protein are present in the CNS parenchyma of MS patients. IgG was purified from CNS tissue of 14 postmortem cases of MS and 8 control cases, including cases of encephalitis. Binding was assessed using two independent assays, a fluorescence-based solid-phase assay and a solution-phase RIA. MOG autoantibodies were identified in IgG purified from CNS tissue by solid-phase immunoassay in 7 of 14 cases with MS and 1 case of subacute sclerosing panencephalitis, but not in IgG from noninflamed control tissue. This finding was confirmed with a solution-phase RIA, which measures higher affinity autoantibodies. These data demonstrate that autoantibodies recognizing MOG are present in substantially higher concentrations in the CNS parenchyma compared with cerebrospinal fluid and serum in subjects with MS, indicating that local production/accumulation is an important aspect of autoantibody-mediated pathology in demyelinating CNS diseases. Moreover, chronic inflammatory CNS disease may induce autoantibodies by virtue of epitope spreading.

Amino Acid Sequence↗
PubMed2005

MicroRNA-21 is an antiapoptotic factor in human glioblastoma cells.

MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate protein expression by targeting the mRNA of protein-coding genes for either cleavage or repression of translation. The roles of miRNAs in lineage determination and proliferation as well as the location of several miRNA genes at sites of translocation breakpoints or deletions has led to the speculation that miRNAs could be important factors in the development or maintenance of the neoplastic state. Here we show that the highly malignant human brain tumor, glioblastoma, strongly over-expresses a specific miRNA, miR-21. Our studies show markedly elevated miR-21 levels in human glioblastoma tumor tissues, early-passage glioblastoma cultures, and in six established glioblastoma cell lines (A172, U87, U373, LN229, LN428, and LN308) compared with nonneoplastic fetal and adult brain tissues and compared with cultured nonneoplastic glial cells. Knockdown of miR-21 in cultured glioblastoma cells triggers activation of caspases and leads to increased apoptotic cell death. Our data suggest that aberrantly expressed miR-21 may contribute to the malignant phenotype by blocking expression of critical apoptosis-related genes.

Apoptosis↗
PubMed2004

A mouse model of cardiac rhabdomyoma generated by loss of Tsc1 in ventricular myocytes.

Tuberous sclerosis is a hamartoma syndrome due to mutations in TSC1 or TSC2 in which cardiac rhabdomyomas are seen in approximately 60% of patients. These lesions have an unusual natural history as they are usually most prominent immediately after birth and spontaneously resolve in most cases. To develop a mouse model of this lesion, we used a conditional, floxed allele of Tsc1 and a modified myosin light chain 2v allele in which cre recombinase expression occurs in ventricular myocytes. Mice with ventricular loss of Tsc1 had a median survival of 6 months and developed a dilated cardiomyopathy with the occurrence of scattered foci of enlarged ventricular myocytes. The enlarged cells were periodic acid-Schiff positive indicating the presence of excess glycogen and expressed elevated levels of phospho-S6, similar to findings in patient rhabdomyoma cells. The observations confirm that rhabdomyomas occur through a two hit mechanism of pathogenesis. However, the mice showed no evidence of fetal/neonatal demise, and there was no evidence of proliferation in the lesions. We propose that these differences are due to the timing of loss of Tsc1 in the ventricular myocytes and/or the truncated gestational period in the mouse compared with humans, during which progestational hormones may accentuate the growth of patient rhabdomyomas.

Alleles↗
PubMed2004

Pathogenesis of tuberous sclerosis subependymal giant cell astrocytomas: biallelic inactivation of TSC1 or TSC2 leads to mTOR activation.

In the central nervous system, tuberous sclerosis complex (TSC) is characterized by a range of lesions including cortical tubers, white matter heterotopias, subependymal nodules, and subependymal giant cell astrocytomas (SEGAs). Recent studies have implicated an important role for the TSC genes TSC1 and TSC2, in a signaling pathway involving the mammalian target of rapamycin (mTOR) kinase. We performed immunohistochemical and genetic analyses on SEGAs from 7 TSC patients, 4 with mutations in TSC1, and 3 with mutations in TSC2. SEGA cells show high levels of phospho-S6K, phospho-S6, and phospho-Stat3, all proteins downstream of and indicative of mTOR activation. Such expression is not seen in histologically normal control tissue. Five of 6 SEGAs also showed evidence of biallelic mutation of TSC1 or TSC2, suggesting that SEGAs develop due to complete loss of a functional tuberin-hamartin complex. We conclude that TSC SEGAs likely arise through a two-hit mechanism of biallelic inactivation of TSC1 or TSC2, leading to activation of the mTOR kinase.

Adolescent↗
PubMed2003

A small-molecule antagonist of CXCR4 inhibits intracranial growth of primary brain tumors.

The vast majority of brain tumors in adults exhibit glial characteristics. Brain tumors in children are diverse: Many have neuronal characteristics, whereas others have glial features. Here we show that activation of the Gi protein-coupled receptor CXCR4 is critical for the growth of both malignant neuronal and glial tumors. Systemic administration of CXCR4 antagonist AMD 3100 inhibits growth of intracranial glioblastoma and medulloblastoma xenografts by increasing apoptosis and decreasing the proliferation of tumor cells. This reflects the ability of AMD 3100 to reduce the activation of extracellular signal-regulated kinases 1 and 2 and Akt, all of which are pathways downstream of CXCR4 that promote survival, proliferation, and migration. These studies (i) demonstrate that CXCR4 is critical to the progression of diverse brain malignances and (ii) provide a scientific rationale for clinical evaluation of AMD 3100 in treating both adults and children with malignant brain tumors.

Animals↗
PubMed2002

EBV-associated lymphoma and chronic inflammatory demyelinating polyneuropathy in an adult without overt immunodeficiency.

Epstein-Barr virus (EBV)-associated lymphoproliferative disease occurs almost exclusively in immunocompromised states. This type of malignancy nevertheless developed in a woman without overt immunocompromise. She presented with rapidly progressive lower extremity weakness that was consistent with a chronic inflammatory demyelinating polyneuropathy (CIDP). CIDP has been documented in Hodgkin's disease but rarely in non-Hodgkin's disease. Diagnosis was confirmed by lymph node and sural nerve biopsies and by nerve conduction studies. Prednisone, rituximab, cyclophosphamide, doxorubicin, and etoposide were administered with regression of lymphadenopathy and improvement in neurologic symptoms. EBV-associated lymphoproliferative disease can thus develop in the absence of overt immunodeficiency and may trigger a demyelinating polyneuropathy.

Aged↗