Howard John Lim

Comparison of different hydrophobic anchors conjugated to poly(ethylene glycol): effects on the pharmacokinetics of liposomal vincristine

Poly(ethylene glycol) (PEG) conjugated lipids have been used to increase the circulation longevity of liposomal carriers encapsulating therapeutic compounds. PEG is typically conjugated to distearoylphosphatidylethanolamine (DSPE) via a carbamate linkage that results in a net negative charge on the phosphate moiety at physiological pH. It was anticipated that the presence of this negative charge could have deleterious effects on liposome pharmacokinetic characteristics. We describe here the synthesis of a new class of neutrally charged PEG-lipid conjugates in which the PEG moiety was linked to ceramide (CER). These PEG-CER conjugates were compared with PEG-DSPE conjugates for their effects on the pharmacokinetics of liposomal vincristine. PEG-CER (78% palmitic acid, C16) and PEG-DSPE achieved comparable increases in the circulation lifetimes of sphingomyelin/cholesterol (SM/chol) liposomes. However, PEG-DSPE significantly increased the in vitro and in vivo leakage rates of vincristine from SM/chol-based liposomes compared to vincristine leakage observed when PEG-CER was used. The increase in drug leakage observed in vitro that was due to the presence of PEG-DSPE was likely due to the presence of a negative surface charge. Analysis of the electrophoretic mobilities of these formulations suggested that the negative surface charges were shielded by approx. 80% by the PEG layer extending from the membrane surface. In contrast, formulations containing PEG-CER had no surface charge and no electrophoretic mobility. A comparison of the effects of the ceramide acyl chain length (C8 through C24) on the pharmacokinetics of SM/chol/PEG-CER formulations of vincristine demonstrated that longer acyl chains on the PEG-CER were associated with longer circulation lifetimes of the liposomal carriers and, consequently, higher plasma vincristine concentrations. These data suggest that the short chain PEG-ceramides underwent rapid partitioning from the vesicles after i.v. administration, whereas the longer chain PEG-ceramides had stronger anchoring properties in the liposome bilayers and partitioned slowly from the administered vesicles. These data demonstrate the utility of ceramide-based steric stabilizing lipids as well as the potential for developing controlled release formulations by manipulating the retention of the PEG-ceramide conjugate in liposome bilayers.

Insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3) overexpression in pancreatic ductal adenocarcinoma correlates with poor survival

BackgroundPancreatic ductal adenocarcinoma is a lethal disease with a 5-year survival rate of 4% and typically presents in an advanced stage. In this setting, prognostic markers identifying the more agrressive tumors could aid in managment decisions. Insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3, also known as IMP3 or KOC) is an oncofetal RNA-binding protein that regulates targets such as insulin-like growth factor-2 (IGF-2) and ACTB (beta-actin).MethodsWe evaluated the expression of IGF2BP3 by immunohistochemistry using a tissue microarray of 127 pancreatic ductal adenocarcinomas with tumor grade 1, 2 and 3 according to WHO criteria, and the prognostic value of IGF2BP3 expression.ResultsIGF2BP3 was found to be selectively overexpressed in pancreatic ductal adenocarcinoma tissues but not in benign pancreatic tissues. Nine (38%) patient samples of tumor grade 1 (n = 24) and 27 (44%) of tumor grade 2 (n = 61) showed expression of IGF2BP3. The highest rate of expression was seen in poorly differentiated specimen (grade 3, n = 42) with 26 (62%) positive samples. Overall survival was found to be significantly shorter in patients with IGF2BP3 expressing tumors (P = 0.024; RR 2.3, 95% CI 1.2-4.8).ConclusionsOur data suggest that IGF2BP3 overexpression identifies a subset of pancreatic ductal adenocarcinomas with an extremely poor outcome and supports the rationale for developing therapies to target the IGF pathway in this cancer.

Lessons learned from the application of whole-genome analysis to the treatment of patients with advanced cancers

Given the success of targeted agents in specific populations it is expected that some degree of molecular biomarker testing will become standard of care for many, if not all, cancers. To facilitate this, cancer centers worldwide are experimenting with targeted “panel” sequencing of selected mutations. Recent advances in genomic technology enable the generation of genome-scale data sets for individual patients. Recognizing the risk, inherent in panel sequencing, of failing to detect meaningful somatic alterations, we sought to establish processes to integrate data from whole-genome analysis (WGA) into routine cancer care. Between June 2012 and August 2014, 100 adult patients with incurable cancers consented to participate in the Personalized OncoGenomics (POG) study. Fresh tumor and blood samples were obtained and used for whole-genome and RNA sequencing. Computational approaches were used to identify candidate driver mutations, genes, and pathways. Diagnostic and drug information were then sought based on these candidate “drivers.” Reports were generated and discussed weekly in a multidisciplinary team setting. Other multidisciplinary working groups were assembled to establish guidelines on the interpretation, communication, and integration of individual genomic findings into patient care. Of 78 patients for whom WGA was possible, results were considered actionable in 55 cases. In 23 of these 55 cases, the patients received treatments motivated by WGA. Our experience indicates that a multidisciplinary team of clinicians and scientists can implement a paradigm in which WGA is integrated into the care of late stage cancer patients to inform systemic therapy decisions.

Phase 2 study of MK-2206, an allosteric inhibitor of AKT, as second-line therapy for advanced gastric and gastroesophageal junction cancer: A SWOG cooperative group trial (S1005)

The AKT inhibitor MK‐2206 at a dose of 60 mg every other day was evaluated in gastric/gastroesophageal junction cancers.

Eligibility of Metastatic Pancreatic Cancer Patients for First-line Palliative Intent nab-paclitaxel Plus Gemcitabine Versus Folfirinox

Objectives: The PRODIGE and MPACT trials showed superiority of FOLFIRINOX and nab-paclitaxel plus gemcitabine (NG) over gemcitabine alone, respectively. However, both had strict inclusion criteria. We sought to determine the characteristics of patients with metastatic pancreatic cancer (MPC) which inform the appropriateness of first-line chemotherapy FOLFIRINOX and NG in routine practice. Materials and Methods: Patients with MPC who initiated palliative chemotherapy with gemcitabine from 2000 to 2011 at the British Columbia Cancer Agency were identified. Clinicopathologic variables and outcomes were retrospectively collected and compared among groups. Eligibility criteria for each regimen were in accordance with the respective pivotal phase III trials. Results: A total of 473 patients were included: 25% of the patients were eligible for FOLFIRINOX versus 45% for NG. Main reasons for FOLFIRINOX ineligibility were Eastern Cooperative Oncology Group (ECOG) performance status (PS)≥2 (56.5%), age older than 75 years (19.0%), and bilirubin>1.5× upper limit of normal (18.6%), whereas those for NG ineligibility were bilirubin > upper limit of normal (24.5%), ECOG PS≥3 (14.6%), and cardiac dysfunction (13.8%). Univariate analyses revealed that FOLFIRINOX and NG-eligible patients had longer median overall survival than their respective ineligible group (8.6 vs. 4.7 mo, P<0.001; 6.7 vs. 4.9 mo, P=0.008, respectively). After accounting for ECOG PS in the multivariate model, however, eligibility for either FOLFIRINOX or NG no longer predicted for better overall survival. Conclusions: The majority of patients with MPC are not candidates to either NG or FOLFIRINOX due to restrictive eligibility requirements. Specific trials addressing the unmet needs of protocol ineligible patients are warranted.

Canadian consensus recommendations on the management of venous thromboembolism in patients with cancer. Part 1: prophylaxis.

Patients with cancer are at increased risk of venous thromboembolism (vte). Anticoagulation therapy has been shown to prevent vte; however, unique clinical circumstances in patients with cancer can often complicate the decisions surrounding the administration of prophylactic anticoagulation. No national Canadian guidelines on the prevention of cancer-associated thrombosis have been published. We therefore aimed to develop a consensus-based, evidence-informed guideline on the topic. PubMed was searched for clinical trials and meta-analyses published between 2002 and 2013. Reference lists of key articles were hand-searched for additional publications. Content experts from across Canada were assembled to review the evidence and make recommendations. Low molecular weight heparin can be used prophylactically in cancer patients at high risk of developing vte. Direct oral anticoagulants are not recommended for vte prophylaxis at this time. Specific clinical scenarios, including renal insufficiency, thrombocytopenia, liver disease, and obesity can warrant modifications in the administration of prophylactic anticoagulant therapy. There is no evidence to support the monitoring of anti-factor Xa levels in clinically stable cancer patients receiving prophylactic anticoagulation; however, factor Xa levels could be checked at baseline and periodically in patients with renal insufficiency. The use of anticoagulation therapy to prolong survival in cancer patients without the presence of risk factors for vte is not recommended.

Nucleophosmin 1, upregulated in adenomas and cancers of the colon, inhibits p53‐mediated cellular senescence

Dysregulation of nucleophosmin 1 (NPM1) has been found in numerous solid and hematological malignancies. Our previous meta‐analysis of colorectal cancer (CRC) high throughput gene expression profiling studies identified it as a consistently reported up‐regulated gene in the malignant state. Our aims were to compare NPM1 expression in normal colon, adenoma and CRC, to correlate their expressions with clinico‐pathological parameters, and to assess the biological role of aberrant NPM1 expression in CRC cells. NPM1 transcript levels were studied in human CRC cell lines, whereas a tissue microarray of 57 normal human colon, 40 adenoma and 185 CRC samples were used to analyze NPM1 protein expression by immunohistochemistry. CRC cell lines were subjected to transient siRNA‐mediated knockdown to study NPM1s roles on cell viability and senescence. NPM1 transcript levels were 7–11‐folds higher in three different human CRC cell lines compared to normal colon cells. NPM1 protein expression was found to be progressively and significantly upregulated in CRC compared to adenomas and in adenomas compared to normal mucosa. Reducing NPM1 expression by siRNA had caused a significant decrease in cell viability, a concomitant increase in cellular senescence and cell cycle arrest. Cellular senescence induced under conditions of forced NPM1 suppression could be prevented by knocking down p53. The differential expression of NPM1 along the normal colon‐adenoma‐carcinoma progression and its involvement in resisting p53 related senescent growth arrest in CRC cell lines implicate its role in supporting CRC tumorigenesis.

Absence of MMP2 Expression Correlates with Poor Clinical Outcomes in Rectal Cancer, and Is Distinct from MMP1-Related Outcomes in Colon Cancer

Purpose: Treatments for colorectal cancer (CRC) are primarily disease stage based. However, heterogeneity in outcome within even a single stage highlights its limitations in predicting disease behavior. Recently, the role of gene expression as predictive and prognostic markers has been explored. Our objectives were to identify consistently differentially expressed genes through meta-analysis of high-throughput gene-expression studies, and evaluate their predictive and prognostic significance in colon (CC) and rectal (RC) cancers. Experimental Design: Publications applying high-throughput gene- expression technologies to specific CRC stages were identified. A vote counting strategy was used to identify the most significant differentially expressed genes. Their predictive and prognostic values were independently assessed in a tissue microarray of 191 cases of stage II-IV CC/RC from two tertiary care centers. Their biological effects were also examined in vitro. Results: MMP1 and MMP2 were identified as consistently underexpressed in liver metastasis compared with primary CRC. Shorter time to distant metastasis and overall survival occurred in stage III CC lacking MMP1 expression, and in stage III RC lacking MMP2. MMP1 levels in stage II and III CC were associated with increased likelihood of distant metastasis, whereas the risk of local recurrence in stage III RC could be stratified by MMP2. Promotion of cell invasion of CRC cell lines exposed to MMP1/2 inhibitors were confirmed in vitro. Conclusions: MMP1 and MMP2 may be useful biomarkers that can help stratify patients at higher risk of developing recurrence in colorectal cancer, and guide individualized treatment decisions to achieve better outcomes. Clin Cancer Res; 17(12); 4167–76. ©2011 AACR.

Survival for Metastatic Colorectal Cancer in the Bevacizumab Era: A Population-based Analysis

BACKGROUND As of 2006, bevacizumab was available for the treatment of metastatic colorectal cancer (mCRC) in British Columbia (BC). This study compares survival between referred patients diagnosed with mCRC in 2003/2004 (pre-bevacizumab era) and 2006 (bevacizumab era). PATIENTS AND METHODS The BC cancer agency (BCCA) is a cancer network treating approximately 60% of patients with mCRC in BC. For this study, all patients in the BCCA diagnosed with mCRC in 2003/2004 and 2006 were included. The primary objective was to compare overall survival (OS) between the 2 cohorts. RESULTS One thousand four hundred seventeen patients were included: 969 from 2003/2004, and 448 from 2006. Between 2003/2004 and 2006, the proportion of patients treated with systemic therapy for mCRC increased (61.1% to 67.6%; P = .02). The only significant difference in treatment between the cohorts was in the proportion of patients who received bevacizumab (5.9% to 30.6%; P < .001). Median OS significantly differed between the 2 cohorts (13.8 to 17.3 months; P < .001). Median OS for patients who received systemic therapy increased (18.6-23.6 months; P = .001). Median OS for patients who did not receive systemic therapy was unchanged (6.1-5.9 months; P = .65). CONCLUSION In this population-based study, median OS for mCRC significantly increased between 2003/2004 and 2006. An increase in the proportion of patients treated with systemic therapy, and the addition of bevacizumab to chemotherapy, seem to have contributed to this improvement in survival.

Outcomes of patients treated with capecitabine and temozolamide for advanced pancreatic neuroendocrine tumors (PNETs) and non-PNETs

BACKGROUND Retrospective studies have demonstrated high response rates among patients with advanced pancreatic neuroendocrine tumors (PNETs) treated with capecitabine and temozolamide (CapTem), while responses are infrequently seen among non-PNETs. The objective of the study was to describe progression free survival (PFS) among neuroendocrine tumor (NET) patients treated with CapTem, and to identify factors associated with better activity. METHODS Patients who were referred to one of five provincial cancer treatment centers between 2009 and 2013 for advanced NETs and initiated CapTem were included. Patients received Cap 1,500 mg/m(2) on days 1-14 and TMZ 200 mg/m(2) on days 10-14 every 28 days. Their characteristics and outcomes were retrospectively analyzed. RESULTS In our cohort, 29 patients (16 males) with a median age of 59 (range 26-76) received palliative CapTem, 15 of them as first-line chemotherapy. Primary tumors included pancreas (48.3%), small bowel (20.7%), lung (10.3%), unknown (10.3%), rectum (6.9%) and appendix (3.4%). Median number of cycles was three. Fifteen patients (51.7%) received CapTem as first-line chemotherapy and 14 (48.3%) as subsequent lines. Median PFS for the entire cohort was 4.7 months. PNETs had a median PFS of 4.9 months compared to 2.8 months for non-PNETs (P=0.178). Patients with PNETs who received CapTem in the first-line setting had a median PFS of 15.9 months as compared to only 3.1 months for the remainder [P=0.047, hazard ratios (HR) 0.342]. Patients with Ki67 above 5% and ≤5% had median PFS of 4.0 and 4.7 months, respectively (P=0.260). CONCLUSIONS CapTem showed good activity among PNETs, but its broader role in the treatment of carcinoid tumors remains unclear.