Stephen Albert Johnston

Lapatinib Combined With Letrozole Versus Letrozole and Placebo As First-Line Therapy for Postmenopausal Hormone Receptor-Positive Metastatic Breast Cancer

PURPOSE Cross-talk between human epidermal growth factor receptors and hormone receptor pathways may cause endocrine resistance in breast cancer. This trial evaluated the effect of adding lapatinib, a dual tyrosine kinase inhibitor blocking epidermal growth factor receptor and human epidermal growth factor receptor 2 (HER2), to the aromatase inhibitor letrozole as first-line treatment of hormone receptor (HR) -positive metastatic breast cancer (MBC). PATIENTS AND METHODS Postmenopausal women with HR-positive MBC were randomly assigned to daily letrozole (2.5 mg orally) plus lapatinib (1,500 mg orally) or letrozole and placebo. The primary end point was progression-free survival (PFS) in the HER2-positive population. Results In HR-positive, HER2-positive patients (n = 219), addition of lapatinib to letrozole significantly reduced the risk of disease progression versus letrozole-placebo (hazard ratio [HR] = 0.71; 95% CI, 0.53 to 0.96; P = .019); median PFS was 8.2 v 3.0 months, respectively. Clinical benefit (responsive or stable disease >or= 6 months) was significantly greater for lapatinib-letrozole versus letrozole-placebo (48% v 29%, respectively; odds ratio [OR] = 0.4; 95% CI, 0.2 to 0.8; P = .003). Patients with centrally confirmed HR-positive, HER2-negative tumors (n = 952) had no improvement in PFS. A preplanned Cox regression analysis identified prior antiestrogen therapy as a significant factor in the HER2-negative population; a nonsignificant trend toward prolonged PFS for lapatinib-letrozole was seen in patients who experienced relapse less than 6 months since prior tamoxifen discontinuation (HR = 0.78; 95% CI, 0.57 to 1.07; P = .117). Grade 3 or 4 adverse events were more common in the lapatinib-letrozole arm versus letrozole-placebo arm (diarrhea, 10% v 1%; rash, 1% v 0%, respectively), but they were manageable. CONCLUSION This trial demonstrated that a combined targeted strategy with letrozole and lapatinib significantly enhances PFS and clinical benefit rates in patients with MBC that coexpresses HR and HER2.

Introduction of foreign genes into tissues of living mice by DNA-coated microprojectiles.

Foreign genes were expressed in liver and skin cells of live mice by using a new apparatus to accelerate DNA-coated microprojectiles into tissues. After introduction of a plasmid in which the firefly luciferase gene was controlled by the human beta-actin promoter, luciferase activity was detectable for up to 14 days in mouse tissues (skin and liver). In situ hybridization histochemistry revealed that microprojectiles penetrated through multiple cell layers without evidence of tissue injury and that 10-20% of the cells in the bombarded area expressed the foreign gene. An advantage of the new design is that internal organs, such as liver, can be transfected without subjecting the tissue to a vacuum. This procedure potentially is applicable to a wide variety of tissues and cell types for studies of transcriptional control elements and for expression of foreign proteins in intact animals.

Phase II Study of Temsirolimus (CCI-779), a Novel Inhibitor of mTOR, in Heavily Pretreated Patients With Locally Advanced or Metastatic Breast Cancer

PURPOSE In this study, two doses of temsirolimus (CCI-779), a novel inhibitor of the mammalian target of rapamycin, were evaluated for efficacy, safety, and pharmacokinetics in patients with locally advanced or metastatic breast cancer who had been heavily pretreated. PATIENTS AND METHODS Patients (n = 109) were randomly assigned to receive 75 or 250 mg of temsirolimus weekly as a 30-minute intravenous infusion. Patients were evaluated for tumor response, time to tumor progression, adverse events, and pharmacokinetics of temsirolimus. RESULTS Temsirolimus produced an objective response rate of 9.2% (10 partial responses) in the intent-to-treat population. Median time to tumor progression was 12.0 weeks. Efficacy was similar for both dose levels but toxicity was more common with the higher dose level, especially grade 3 or 4 depression (10% of patients at the 250-mg dose level, 0% at the 75-mg dose level). The most common temsirolimus-related adverse events of all grades were mucositis (70%), maculopapular rash (51%), and nausea (43%). The most common, clinically important grade 3 or 4 adverse events were mucositis (9%), leukopenia (7%), hyperglycemia (7%), somnolence (6%), thrombocytopenia (5%), and depression (5%). CONCLUSION In heavily pretreated patients with locally advanced or metastatic breast cancer, 75 and 250 mg temsirolimus showed antitumor activity and 75 mg temsirolimus showed a generally tolerable safety profile.

Molecular Changes in Tamoxifen-Resistant Breast Cancer: Relationship Between Estrogen Receptor, HER-2, and p38 Mitogen-Activated Protein Kinase

PURPOSE To evaluate growth factor receptor cross talk with the estrogen receptor (ER) in paired clinical breast cancer specimens and in a xenograft model before tamoxifen and at tumor progression as a possible mechanism for tamoxifen resistance. METHODS Specimen pairs from 39 patients were tissue arrayed and stained for ER, progesterone receptor (PgR), Bcl-2, c-ErbB2 (HER-2), and phosphorylated (p) p38 mitogen-activated protein kinase (MAPK), p-ERK1/2 MAPK, and p-Akt. Xenograft MCF-7 tumors before and after tamoxifen resistance were assessed for levels of p-p38. RESULTS Pretreatment, there were strong correlations between ER, PgR, and Bcl-2, and an inverse correlation between ER and HER-2. These correlations were lost in the tamoxifen- resistant tumors and replaced by strong correlations between ER and p-p38 and p-ERK. ER expression was lost in 17% of resistant tumors. Three (11%) of the 26 tumors originally negative for HER-2 became amplified and/or overexpressed at resistance. All ER-positive tumors that overexpressed HER-2 originally or at resistance expressed high levels of p-p38. In the pretreatment and tamoxifen-resistant specimens, there were strong correlations between p-p38 and p-ERK. In the tamoxifen-resistant xenograft tumors, like the clinical samples, there was a striking increase in p-p38. CONCLUSION The molecular pathways driving tumor growth can change as the tumor progresses. Crosstalk between ER, HER-2, p38, and ERK may contribute to tamoxifen resistance and may provide molecular targets to overcome this resistance.

The 19S regulatory particle of the proteasome is required for efficient transcription elongation by RNA polymerase II

It is generally thought that the primary or even sole activity of the 19S regulatory particle of the 26S proteasome is to facilitate the degradation of polyubiquitinated proteins by the 20S-core subunit. However, we present evidence that the 19S complex is required for efficient elongation of RNA polymerase II (RNAP II) in vitro and in vivo. First, yeast strains carrying alleles of SUG1 and SUG2, encoding 19S components, exhibit phenotypes indicative of elongation defects. Second, in vitro transcription is inhibited by antibodies raised against Sug1, or by heat-inactivating temperature-sensitive Sug1 mutants with restoration of elongation by addition of immunopurified 19S complex. Finally, Cdc68, a known elongation factor, coimmunoprecipitates with the 19S complex, indicating a physical interaction. Inhibition of the 20S proteolytic core of the proteasome has no effect on elongation. This work defines a nonproteolytic role for the 19S complex in RNAP II transcription.

Biological features of genetic immunization

Genetic immunization (a.k.a. DNA-based immunization) shows promise at least as a convenient method to test and discover new vaccines and may be an efficient vaccine delivery system. However, relatively little is known about the parameters affecting its effectiveness, let alone its basic underlying biological mechanisms. Here we report on investigations of some of the factors that determine the quantity and quality of the immune response with genetic immunization. We find that for non-toxic proteins the antibody response correlates well with the level of expression as does the cellular response to a certain level. The augmentation of the immune response by co-introduction of a cytokine gene as a genetic adjuvant is also responsive to the expression level of the antigen. The immune response is inversely correlated to the age of the mice and at least part of this effect is through level of expression of the antigen. Gene gun administration of the transgene to the skin has the advantage over muscle injection in that ca 100-fold less DNA is required for the same level of expression and the injections are more reproducible in effect. Finally, the apparent differences in Th2 (gun) vs Th1 (muscle) responses between the two modes can at least partly be accounted for by differences in the amount of plasmid DNA typically administered.

The 19S Regulatory Complex of the Proteasome Functions Independently of Proteolysis in Nucleotide Excision Repair

The 26S proteasome degrades proteins targeted by the ubiquitin pathway, a function thought to explain its role in cellular processes. The proteasome interacts with the ubiquitin-like N terminus of Rad23, a nucleotide excision repair (NER) protein, in Saccharomyces cerevisiae. Deletion of the ubiquitin-like domain causes UV radiation sensitivity. Here, we show that the ubiquitin-like domain of Rad23 is required for optimal activity of an in vitro NER system. Inhibition of proteasomal ATPases diminishes NER activity in vitro and increases UV sensitivity in vivo. Surprisingly, blockage of protein degradation by the proteasome has no effect on the efficiency of NER. This establishes that the regulatory complex of the proteasome has a function independent of protein degradation.

Phase II Study of Predictive Biomarker Profiles for Response Targeting Human Epidermal Growth Factor Receptor 2 (HER-2) in Advanced Inflammatory Breast Cancer With Lapatinib Monotherapy

PURPOSE Inflammatory breast cancer (IBC) is one of the most aggressive forms of breast cancer. Lapatinib, an oral reversible inhibitor of epidermal growth factor receptor (EGFR) and human EGFR 2 (HER-2), demonstrated clinical activity in four of five IBC patients in phase I trials. We conducted a phase II trial to confirm the sensitivity of IBC to lapatinib, to determine whether response is HER-2 or EGFR dependent, and to elucidate a molecular signature predictive of lapatinib sensitivity. PATIENTS AND METHODS Our open-label multicenter phase II trial (EGF103009) assessed clinical activity and safety of lapatinib monotherapy in patients with recurrent or anthracycline-refractory IBC. Patients were assigned to cohorts A (HER-2-overexpressing [HER-2+]) or B(HER-2-/EGFR+) and fresh pretreatment tumor biopsies were collected. RESULTS Forty-five patients (30 in cohort A; 15 in cohort B) received lapatinib 1,500 mg once daily continuously. Clinical presentation and biomarker analyses demonstrated a tumor molecular signature consistent with IBC. Lapatinib was generally well tolerated, with primarily grade 1/2 skin and GI toxicities. Fifteen patients (50%) in cohort A had clinical responses to lapatinib in skin and/or measurable disease (according to Response Evaluation Criteria in Solid Tumors) compared with one patient in cohort B. Within cohort A, phosphorylated (p) HER-3 and lack of p53 expression predicted for response to lapatinib (P < .05). Tumors coexpressing pHER-2 and pHER-3 were more likely to respond to lapatinib (nine of 10 v four of 14; P = .0045). Prior trastuzumab therapy and loss of phosphate and tensin homolog 10 (PTEN) did not preclude response to lapatinib. CONCLUSION Lapatinib is well tolerated with clinical activity in heavily pretreated HER-2+, but not EGFR+/HER-2-, IBC. In this study, coexpression of pHER-2 and pHER-3 in tumors seems to predict for a favorable response to lapatinib. These findings warrant further investigation of lapatinib monotherapy or combination therapy in HER-2+ IBC.

Genome-directed primers for selective labeling of bacterial transcripts for DNA microarray analysis.

DNA microarrays have the ability to analyze the expression of thousands of the same set of genes under at least two different experimental conditions. However, DNA microarrays require substantial amounts of RNA to generate the probes, especially when bacterial RNA is used for hybridization (50 μg of bacterial total RNA contains approximately 2 μg of mRNA). We have developed a computer-based algorithm for prediction of the minimal number of primers to specifically anneal to all genes in a given genome. The algorithm predicts, for example, that 37 oligonucleotides should prime all genes in the Mycobacterium tuberculosis genome. We tested the usefulness of the genome-directed primers (GDPs) in comparison to random primers for gene expression profiling using DNA microarrays. Both types of primers were used to generate fluorescent-labeled probes and to hybridize to an array of 960 mycobacterial genes. Compared to random-primer probes, the GDP probes were more sensitive and more specific, especially when mammalian RNA samples were spiked with mycobacterial RNA. The GDPs were used for gene expression profiling of mycobacterial cultures grown to early log or stationary growth phases. This approach could be useful for accurate genome-wide expression analysis, especially for in vivo gene expression profiling, as well as directed amplification of sequenced genomes.

GAL4 INTERACTS WITH TATA-BINDING PROTEIN AND COACTIVATORS

A major goal in understanding eukaryotic gene regulation is to identify the target(s) of transcriptional activators. Efforts to date have pointed to various candidates. Here we show that a 34-amino-acid peptide from the carboxy terminus of GAL4 is a strong activation domain (AD) and retains at least four proteins from a crude extract: the negative regulator GAL80, the TATA-binding protein (TBP), and the putative coactivators SUG1 and ADA2. TFIIB was not retained. Concentrating on TBP, we demonstrate in in vitro binding assays that its interaction with the AD is specific, direct, and salt stable up to at least 1.6 M NaCl. The effects of mutations in the GAL4 AD on transcriptional activation in vivo correlate with their affinities to TBP. A point mutation (L114K) in yeast TBP, which has been shown to compromise the mutant protein in both binding to the VP16 AD domain and activated transcription in vitro, reduces the affinity to the GAL4 AD to the same degree as to the VP16 AD. This suggests that these two prototypic activators make similar contacts with TBP.