Sex Representation in Clinical Trials Associated with FDA Cancer Drug Approvals Differs Between Solid and Hematologic Malignancies.

BACKGROUND: Proportionate female representation in health research is necessary for scientific rigor and health equity. We aimed to assess the representation of women in clinical trials leading to U.S. Food and Drug Administration (FDA) cancer drug approvals. MATERIALS AND METHODS: Trials supporting FDA cancer drug approvals between July 2008 and June 2018 were sourced from PubMed and ClinicalTrials.gov. The ratio of female to male trial enrollment was compared with cancer incidence and mortality in the U.S. using International Agency for Research on Cancer data. Reproductive tract and breast cancers were excluded. Odds ratios (ORs) and 95% confidence intervals (CIs) comparing trial enrollment with population incidence and mortality were calculated. RESULTS: A total of 186 trials leading to 170 FDA cancer drug approvals showed slight female underrepresentation compared with overall cancer incidence in the U.S. (OR, 0.97; 95% CI, 0.95-0.98, p < .0001). Female enrollment for drugs approved between 2008-2013 and 2014-2018 was unchanged (OR, 1.02; 95% CI, 0.99-1.05, p = .25). There was slight female underrepresentation in hematological trials (OR, 0.95; 95% CI, 0.91-0.998; p = .040 for leukemia; OR, 0.95; 95% CI, 0.90-0.997; p = .040 for lymphoma) and significant female underrepresentation in colorectal (OR, 0.72; 95% CI, 0.69-0.76; p < .0001), pancreas (OR, 0.85; 95% CI, 0.78-0.93; p = .0004), lung (OR, 0.77; 95% CI, 0.75-0.80; p < .0001), kidney (OR, 0.63; 95% CI, 0.60-0.67; p < .0001), and thyroid cancer trials (OR, 0.26; 95% CI, 0.23-0.28; p < .0001) compared with U.S. incidence. CONCLUSION: Female underrepresentation has persisted within solid organ tumor trials but is less notable in hematologic trials. Additional work is required to identify drivers of such disparity. IMPLICATIONS FOR PRACTICE: Adequate gender representation in clinical trials is a matter of health equity. This study demonstrates that women remain underrepresented in trials across hematological and solid organ trials compared with cancer incidence and mortality in women, with the disparity worse in a number of solid organ tumor types. There are thus still significant improvements to be made regarding adequate representation of women in trials. Studies exploring the reasons for ongoing disparity in gender representation are warranted to help clinicians to rectify this.

TP53 loss creates therapeutic vulnerability in colorectal cancer.

TP53, a well-known tumour suppressor gene that encodes p53, is frequently inactivated by mutation or deletion in most human tumours. A tremendous effort has been made to restore p53 activity in cancer therapies. However, no effective p53-based therapy has been successfully translated into clinical cancer treatment owing to the complexity of p53 signalling. Here we demonstrate that genomic deletion of TP53 frequently encompasses essential neighbouring genes, rendering cancer cells with hemizygous TP53 deletion vulnerable to further suppression of such genes. POLR2A is identified as such a gene that is almost always co-deleted with TP53 in human cancers. It encodes the largest and catalytic subunit of the RNA polymerase II complex, which is specifically inhibited by α-amanitin. Our analysis of The Cancer Genome Atlas (TCGA) and Cancer Cell Line Encyclopedia (CCLE) databases reveals that POLR2A expression levels are tightly correlated with its gene copy numbers in human colorectal cancer. Suppression of POLR2A with α-amanitin or small interfering RNAs selectively inhibits the proliferation, survival and tumorigenic potential of colorectal cancer cells with hemizygous TP53 loss in a p53-independent manner. Previous clinical applications of α-amanitin have been limited owing to its liver toxicity. However, we found that α-amanitin-based antibody-drug conjugates are highly effective therapeutic agents with reduced toxicity. Here we show that low doses of α-amanitin-conjugated anti-epithelial cell adhesion molecule (EpCAM) antibody lead to complete tumour regression in mouse models of human colorectal cancer with hemizygous deletion of POLR2A. We anticipate that inhibiting POLR2A will be a new therapeutic approach for human cancers containing such common genomic alterations.

It Is Time to Re-Evaluate the Peer Review Process for Preclinical Research.

Problems in peer review, the backbone of maintaining high standards in scientific publishing, have led to wide spread discontent within the scientific community. Training in the peer review process and a simpler format to assist in decision making are possible courses to improve and expedite the process of peer review and scientific publishing.

Intracrine VEGF signalling mediates colorectal cancer cell migration and invasion.

BACKGROUND: Vascular endothelial growth factor (VEGF) and its receptors (VEGFRs) are key regulators of angiogenesis, affecting endothelial cell survival and function. However, the effect of VEGF-VEGFR signalling on tumour cell function is not well understood. Our previous studies in colorectal cancer (CRC) cells have demonstrated an intracrine VEGF/VEGFR1 signalling mechanism that mediates CRC cell survival and chemo-sensitivity. Since extracellular VEGF signalling regulates migration of endothelial cells and various tumour cells, we attempted to determine whether intracrine VEGF signalling affects CRC cell motility. METHODS: Migration and invasion of CRC cells, with and without VEGF or VEGFR1 depletion, were assayed using transwell migration chambers. Changes in cell morphology, epithelial-mesenchymal transition (EMT) markers, and markers of cell motility were assessed by immunostaining and western blot. RESULTS: Depletion of intracellular VEGF and VEGFR1 in multiple CRC cell lines led to strong inhibition of migration and invasion of CRC cells. Except for Twist, there were no significant differences in markers of EMT between control and VEGF/VEGFR1-depleted CRC cells. However, VEGF/VEGFR1-depleted CRC cells demonstrated a significant reduction in levels of phosphorylated focal adhesion kinase and its upstream regulators pcMET and pEGFR. CONCLUSIONS: Inhibition of intracrine VEGF signalling strongly inhibits CRC cell migration and invasion by regulating proteins involved in cell motility.

Antiangiogenic therapy in oncology: current status and future directions.

Angiogenesis, the formation of new blood vessels from pre-existing vessels, has been validated as a target in several tumour types through randomised trials, incorporating vascular endothelial growth factor (VEGF) pathway inhibitors into the therapeutic armoury. Although some tumours such as renal cell carcinoma, ovarian and cervical cancers, and pancreatic neuroendocrine tumours are sensitive to these drugs, others such as prostate cancer, pancreatic adenocarcinoma, and melanoma are resistant. Even when drugs have yielded significant results, improvements in progression-free survival, and, in some cases, overall survival, are modest. Thus, a crucial issue in development of these drugs is the search for predictive biomarkers-tests that predict which patients will, and will not, benefit before initiation of therapy. Development of biomarkers is important because of the need to balance efficacy, toxicity, and cost. Novel combinations of these drugs with other antiangiogenics or other classes of drugs are being developed, and the appreciation that these drugs have immunomodulatory and other modes of action will lead to combination regimens that capitalise on these newly understood mechanisms.

Intracellular signaling in tumor and endothelial cells: The expected and, yet again, the unexpected.

In this issue of Cancer Cell, Phung and coworkers demonstrate that sustained endothelial activation of Akt by expression of constitutively activated Akt1 (myrAkt1) leads to blood vessels that essentially recapitulate the complex structural and functional abnormalities of tumor vessels. The authors provide evidence that rapamycin inhibition of PI3K/Akt/mTOR signaling in endothelial cells (ECs), by either reducing Akt activity or blocking mTOR, reverses the pathologic effects associated with excess VEGF signaling in the tumor vasculature. However, unexpected findings following mTOR inhibition in vivo highlight the seemingly paradoxical and complex effects of rapamycin on various cell types within the tumor microenvironment.

Morbidity of staged proctectomy after hepatectomy for colorectal cancer: a matched case-control analysis.

BACKGROUND: Proctectomy after hepatectomy, or the reverse approach, is an alternative to traditional sequencing for advanced liver metastases with asymptomatic colorectal primary tumors. We sought to evaluate the surgical morbidity of proctectomy for colorectal cancer after previous liver surgery. METHODS: A single-institution colorectal database was queried for patients treated with proctectomy after previous hepatectomy from 2003 to 2011. Reverse-approach patients (n = 31) were matched 1:2 with a cohort of standard proctectomy patients (n = 62) using operation, age, gender, and surgeon. Perioperative factors were analyzed by univariate/multivariate models for associations with complications graded by Dindo-Clavien criteria. RESULTS: Thirty-one patients with adenocarcinoma ≤ 20 cm from the anal verge underwent proctectomy after hepatectomy. Median time from hepatectomy to proctectomy was 5.1 months. Median tumor distance was 8.5 cm. Before proctectomy, patients underwent 28 (90 %) major hepatectomies and 7 (22 %) portal vein embolizations. There were no perioperative deaths. Reverse-approach patients did not differ from control patients in operation, demographics, body mass index (BMI), comorbidities, tumor distance, operative time, estimated blood loss, length of stay, or complication rates (p > 0.05). Grade 2 or higher complications developed in 42 % of reverse-approach and 27 % of standard proctectomies (p = 0.17). Grade 3 or higher complications developed in 10 % and 8 %, respectively (p = 1.00). Independent predictors of complications of grade 2 or higher were BMI ≥30 kg/m(2) (p = 0.007), operative time ≥300 min (p = 0.012), intraoperative transfusion (p = 0.044), concurrent procedures (p = 0.024), and age ≥50 years (p = 0.030). CONCLUSIONS: Risk factors for morbidity of staged proctectomy are similar to those for standard proctectomy. In selected patients, the reverse-approach proctectomy is safe with acceptable morbidity.

Combining MEK and SRC inhibitors for treatment of colorectal cancer demonstrate increased efficacy in vitro but not in vivo.

Metastatic colorectal cancer (mCRC) is the second leading cause of cancer deaths in the United States. More than 50% of patients with mCRC harbor mutations of the oncogenic driver RAS (KRAS or NRAS). Because directly targeting most mutations of RAS is technically challenging, researchers have concentrated on targeting MEK, a downstream mediator of RAS. However, targeting MEK as single-agent therapy is ineffective in patients with mCRC. We hypothesize that combining a MEK inhibitor with other agents can enhance the efficacy of MEK targeting in mCRC. Unbiased high-throughput screening (HTS) was performed to identify drugs that enhance the efficacy of MEK inhibitors. HTS was performed with KRAS-mutated CRC cells using the MEK inhibitor trametinib as a "backbone" and two "clinically ready" compound libraries approved by the U.S. Food and Drug Administration or in clinical trials. HTS demonstrated that the combination of the SRC inhibitor dasatinib and trametinib was synergistic in CRC cells in vitro (MTT and colony formation assays). Analysis of markers for cell proliferation and apoptosis using fluorescence-activated cell sorting, reverse-phase protein array, or Western blotting demonstrated decreased cell proliferation and increased cell death when targeting both SRC and MEK as compared to single agents in multiple CRC cell lines. However, combining dasatinib and trametinib in vivo at doses in mice equivalent to doses used in humans failed to significantly enhance the antitumor activity of trametinib when compared to that of trametinib alone. These results underscore the importance of performing careful preclinical in vivo validation studies using clinically relevant doses as a prerequisite for translating in vitro findings to the clinic.

Vincristine Enhances the Efficacy of MEK Inhibitors in Preclinical Models of KRAS-mutant Colorectal Cancer.

Mutations in KRAS are found in more than 50% of tumors from patients with metastatic colorectal cancer (mCRC). However, direct targeting of most KRAS mutations is difficult; even the recently developed KRASG12C inhibitors failed to show significant benefit in patients with mCRC. Single agents targeting mitogen-activated protein kinase kinase (MEK), a downstream mediator of RAS, have also been ineffective in colorectal cancer. To identify drugs that can enhance the efficacy of MEK inhibitors, we performed unbiased high-throughput screening using colorectal cancer spheroids. We used trametinib as the anchor drug and examined combinations of trametinib with the NCI-approved Oncology Library version 5. The initial screen, and following focused validation screens, identified vincristine as being strongly synergistic with trametinib. In vitro, the combination strongly inhibited cell growth, reduced clonogenic survival, and enhanced apoptosis compared with monotherapies in multiple KRAS-mutant colorectal cancer cell lines. Furthermore, this combination significantly inhibited tumor growth, reduced cell proliferation, and increased apoptosis in multiple KRAS-mutant patient-derived xenograft mouse models. In vivo studies using drug doses that reflect clinically achievable doses demonstrated that the combination was well tolerated by mice. We further determined that the mechanism underlying the synergistic effect of the combination was due to enhanced intracellular accumulation of vincristine associated with MEK inhibition. The combination also significantly decreased p-mTOR levels in vitro, indicating that it inhibits both RAS-RAF-MEK and PI3K-AKT-mTOR survival pathways. Our data thus provide strong evidence that the combination of trametinib and vincristine represents a novel therapeutic option to be studied in clinical trials for patients with KRAS-mutant mCRC. SIGNIFICANCE: Our unbiased preclinical studies have identified vincristine as an effective combination partner for the MEK inhibitor trametinib and provide a novel therapeutic option to be studied in patients with KRAS-mutant colorectal cancer.

Genetic variants within ultraconserved elements and susceptibility to right- and left-sided colorectal adenocarcinoma.

We investigated whether single nucleotide polymorphisms within ultraconserved elements (UCEs) are associated with susceptibility to overall colorectal cancer (CRC) and susceptibility to tumor site-specific CRC. The study included 787 CRC patients and 551 healthy controls. The study comprised of a training set (520 cases and 341 controls) and a replication set (267 cases and 210 controls). We observed associations in rs7849 and rs1399685 with CRC risk. For example, a dose-dependent trend (per-allele odds ratio (OR), 0.78; 95% confidence interval (CI), 0.63-1.00; P for trend = 0.05) associated with the variant allele of rs7849 in the training set. The significant trend toward a decrease in CRC risk was confirmed in the replication set (per-allele OR, 0.72; 95% CI, 0.52-0.99; P for trend = 0.044). When stratified by tumor location, for left-sided CRC (LCRC) risk, significant association was observed for the variant-containing genotypes of rs1399685 (OR, 1.77; 95% CI, 1.02-3.06) and the risk was replicated in the replication population (OR, 2.04; 95% CI, 1.02-4.07). The variant genotypes of rs9784100 and rs7849 conferred decreased risk but the associations were not replicated. Three right-sided CRC (RCRC) susceptibility loci were identified in rs6124509, rs4243289 and rs12218935 but none of the loci was replicated. Joint effects and potential higher order gene-gene interactions among significant variants further categorized patients into different risk groups. Our results strongly suggest that several genetic variants in the UCEs may contribute to CRC susceptibility, individually and jointly, and that different genetic etiology may be involved in RCRC and LCRC.

GWAS-identified colorectal cancer susceptibility loci associated with clinical outcomes.

Recent genome-wide association studies (GWAS) have identified several common susceptibility loci associated with the risk of colorectal cancer (CRC). However, whether these loci affect clinical outcomes of CRC is not clear. In this study, we genotyped 26 single nucleotide polymorphisms (SNPs) in 10 GWAS-identified CRC susceptibility regions and evaluated their associations with survival and recurrence in 285 stage II and III patients receiving fluorouracil-based adjuvant chemotherapy. Only one SNP, rs10318 (15q13.3), was significantly associated with recurrence for patients with stage II disease. Three SNPs: rs10749971 (11q23.1), rs961253 (20p12.3) and rs355527 (20p12.3) in two regions were significantly associated with recurrence for patients with stage III disease. Five SNPs: rs961253 (20p12.3), rs355527 (20p12.3), rs4464148 (18q21.1), rs6983267 (8q24.21) and rs10505477 (8q24.21) in three regions were significantly associated with survival for patients with stage III disease. Cumulative effects of multiple unfavorable genotypes were observed for recurrence and survival in patients with stage III CRC. Our results suggest that cancer susceptibility loci may also affect the prognosis of CRC patients receiving fluorouracil-based adjuvant chemotherapy.

Identification of polymorphisms in ultraconserved elements associated with clinical outcomes in locally advanced colorectal adenocarcinoma.

BACKGROUND: Ultraconserved elements (UCEs) are noncoding genomic sequences that completely identical among human, mouse, and rat species and harbor critical biologic functions. The authors hypothesized that single nucleotide polymorphisms (SNPs) within UCEs are associated with clinical outcomes in patients with colorectal cancer (CRC). METHODS: Forty-eight SNPs within UCEs were genotyped in 662 patients with stage I through III CRC. The associations between genotypes and recurrence and survival were analyzed in patients with stage II or III CRC who received fluoropyrimidine-based adjuvant chemotherapy using a training and validation design. The training set included 115 patients with stage II disease and 170 patients with stage III disease, and the validation set included 88 patients with stage II disease and 112 patients with stage III disease. RESULTS: Eight SNPs were associated with clinical outcomes stratified by disease stage. In particular, for patients with stage II CRC who had at least 1 variant allele of reference SNP sequence 7849 (rs7849), a consistent association with increased recurrence risk was observed in the training set (hazard ratio [HR], 2.39; 95% confidence interval [CI], 1.04-5.52), in the replication set (HR, 3.70; 95% CI, 1.42-9.64), and in a meta-analysis (HR, 2.89; 95% CI, 1.54-5.41). Several other SNPs were significant in the training set but not in the validation set. These included rs2421099, rs16983007, and rs10211390 for recurrence and rs6590611 for survival in patients with stage II disease; and SNPs rs6124509 and rs11195893 for recurrence in patients with stage III disease. In addition, a significant cumulative effect was observed of multiple risk genotypes and potential gene-gene interactions on recurrence risk. CONCLUSIONS: To the authors' knowledge, this is the first study to evaluate the association between SNPs within UCEs and clinical outcome in patients with CRC. The results suggested that SNPs within UCEs may be valuable prognostic biomarkers for patients with locally advanced CRC who receive 5-fluorouracil-based chemotherapy.

Identification of cancer stem cells in human gastrointestinal carcinoid and neuroendocrine tumors.

BACKGROUND & AIMS: Metastatic gastrointestinal neuroendocrine tumors (NETs) frequently are refractory to chemotherapy. Chemoresistance in various malignancies has been attributed to cancer stem cells (CSCs). We sought to identify gastrointestinal neuroendocrine CSCs (N-CSCs) in surgical specimens and a NET cell line and to characterize novel N-CSC therapeutic targets. METHODS: Human gastrointestinal NETs were evaluated for CSCs using the Aldefluor (Stemcell Technologies, Vancouver, Canada) assay. An in vitro, sphere-forming assay was performed on primary NET cells. CNDT2.5, a human midgut carcinoid cell line, was used for in vitro (sphere-formation) and in vivo (tumorigenicity assays) CSC studies. N-CSC protein expression was characterized using Western blotting. In vivo, systemic short interfering RNA administration targeted Src. RESULTS: By using the Aldefluor assay, aldehyde dehydrogenase-positive (ALDH+) cells comprised 5.8% ± 1.4% (mean ± standard error of the mean) of cells from 19 patient samples. Although many primary cell lines failed to grow, CNDT96 ALDH+ cells formed spheres in anchorage-independent conditions, whereas ALDH- cells did not. CNDT2.5 ALDH+ cells formed spheres, whereas ALDH- cells did not. In vivo, ALDH+ CNDT2.5 cells generated more tumors, with shorter latency than ALDH- or sham-sorted cells. Compared with non-CSCs, ALDH+ cells demonstrated increased expression of activated Src, Erk, Akt, and mammalian target of rapamycin (mTOR). In vivo, anti-Src short interfering RNA treatment of ALDH+ tumors reduced tumor mass by 91%. CONCLUSIONS: CSCs are present in NETs, as shown by in vitro sphere formation and in vivo tumorigenicity assays. Src was activated in N-CSCs and represents a potential therapeutic target in gastrointestinal NETs.

Cytospin-A Regulates Colorectal Cancer Cell Division and Migration by Modulating Stability of Microtubules and Actin Filaments.

Proteins that interact with cytoskeletal elements play important roles in cell division and are potentially important targets for therapy in cancer. Cytospin-A (CYTSA), a protein known to interact with actin and microtubules, has been previously described to be important in various developmental disorders, including oblique facial clefting. We hypothesized that CYTSA plays an important role in colorectal cancer (CRC) cell division. The effects of CYTSA depletion on CRC cell proliferation were analyzed using cell growth assays, microscopic analyses of live and fixed cells, and time-lapse imaging. CYTSA depletion led to inhibition of cell proliferation, significant increases in CRC cell death, and accumulation of doublet cells during and following cell division. Depletion of CYTSA also resulted in strong inhibition of CRC cell migration and invasion. Mechanistically, CYTSA depletion resulted in significant decreases in the stability of microtubules and altered polymerization of actin filaments in CRC cells. Finally, bioinformatic analyses were performed to determine the correlation between CYTSA expression and survival of patients with CRC. Interestingly, a strong correlation between high CYTSA expression and poor survival was observed in the TCGA adenocarcinoma data set but not in an independent data set. Since inhibiting CYTSA significantly reduces CRC cell proliferation, migration, and invasion, targeting CYTSA may be a potential novel therapeutic option for patients with metastatic CRC.

Overall Survival in Phase 3 Clinical Trials and the Surveillance, Epidemiology, and End Results Database in Patients With Metastatic Colorectal Cancer, 1986-2016: A Systematic Review.

Importance: Phase 3 trials for patients with metastatic colorectal cancer (mCRC) have been conducted with varying designs and often with surrogate end points for overall survival (OS). Objectives: To critically examine the factors associated with clinically relevant improvement in OS (defined as ≥2 months) in these trials and to evaluate their association with outcomes reflected in Surveillance, Epidemiology, and End Results (SEER) registry data. Evidence Review: Medline, EMBASE, Cochrane, Web of Science, ClinicalTrials.gov, EU Clinical Trials Register, and the International Clinical Trials Registry Platform were searched for phase 3 trials of systemic therapy for patients with mCRC by decade (1986-1996, 1997-2006, and 2007-2016), excluding early or pilot studies, studies that did not involve an anticancer drug, studies on cancer screening and prevention, reports of pooled data from multiple trials, and studies with nonpharmaceutical approaches. The association of drug development with OS outside the clinical trial setting was evaluated using data from the SEER registry, including adult patients with a primary cancer site in the colon or rectum, including adenocarcinoma, mucinous adenocarcinoma, or signet ring cell carcinoma; a distant stage; and receipt of chemotherapy as first-line therapy. Kaplan-Meier curves and log-rank tests were used to assess OS. Findings: The literature search identified 150 phase III clinical trials with 77 494 total enrollments, and 67 126 patients with mCRC were identified from the SEER database. Significant increases in survival were noted over time, best reflected in the experimental arm of first-line therapy (OS increased by 5.7 months per 10 years; 95% CI, 4.7-6.6 months; progression-free survival increased by 1.4 months per 10 years; 95% CI, 0.7-2.1 months). Although 69 of 148 trials (46.6%) met their predefined primary end point (including 20 of 44 trials [45.5%] with OS as the primary end point), only 35 of 132 trials (26.5%) resulted in improvement in OS by 2 months or more (including 13 of 42 trials [31.0%] with OS as the primary end point). Multivariable logistic regression showed that third-line therapies or later (odds ratio, 0.57; 95% CI, 0.51-0.63) and funding by pharmaceutical companies (odds ratio, 0.57; 95% CI, 0.54-0.60) were less often associated with improvement in OS. Furthermore, there was a decrease in the novelty of targets and agents over time, with trials that evaluated regimens composed entirely of previously approved drugs for mCRC increasing from 28% to 50%. Data from the SEER database showed that median OS increased from 12 months (95% CI, 12-13 months) (1986-1996) to 21 months (95% CI, 21-22 months) (2007-2015) (P < .001), but the 5-year OS continued to be low at 12.2% in 2011. Conclusions and Relevance: In this systematic review, OS for patients with mCRC appeared to improve significantly in trials, translating into meaningful benefits outside the clinical trial setting; however, these advances, although significant cumulatively, are largely incremental individually. These data should be a call to aim for larger gains from future trials with novel drugs, building on the increasing understanding of the biology of mCRC and sophisticated translational research tools.