Stem cell property epithelial-to-mesenchymal transition is a core transcriptional network for predicting cetuximab (Erbitux™) efficacy in KRAS wild-type tumor cells

Therapeutic antibodies for the prevention and treatment of cancer

The developments of antibodies for cancer therapeutics have made remarkable success in recent years. There are multiple factors contributing to the success of the biological molecule including origin of the antibody, isotype, affinity, avidity and mechanism of action. With better understanding of mechanism of cancer progression and immune manipulation, recombinant formats of antibodies are used to develop therapeutic modalities for manipulating the immune cells of patients by targeting specific molecules to control the disease. These molecules have been successful in minimizing the side effects instead caused by small molecules or systemic chemotherapy but because of the developing therapeutic resistance against these antibodies, combination therapy is thought to be the best bet for patient care. Here, in this review, we have discussed different aspects of antibodies in cancer therapy affecting their efficacy and mechanism of resistance with some relevant examples of the most studied molecules approved by the US FDA.

Facile calcium ion-regulated grafting of dense and highly stretched hyaluronan for selective mediation of cancer cells rolling under high-speed flow

The development of materials that selectively mediate the rolling of cancer cells is important for the high-throughput enrichment of high-speed cancer cells. Here we constructed a dense and stretched low molecular weight hyaluronic acid (HA_9.6k)-modified surface to selectively promote the rolling of CD44-high cancer cells. The HA surface (calcium ion-regulated HA_9.6k surface, Ca-rHA) was fabricated via a calcium ion-regulated method, where calcium ion incorporation induced the shrink of HA_9.6k chains to achieve the highest reported grafting density of about 2.73 ± 0.20 × 10⁴ HA chains μm^-2. Upon the removal of calcium ions, the dense HA_9.6k chains switched to a highly stretched conformation. The high density and flexibility of Ca-rHA bearing abundant binding sites enhanced the rolling of CD44-high cancer cells and reduced the velocity of cells from 1389 µm s^-1 to 99 µm s^-1 (7%), comparable to that of the physiological rolling event and outperforming traditional grafting-to HA and E-selectin, without causing phenotypic changes. When processing complex samples under high-speed flow, Ca-rHA selectively mediated the rolling of cancer cells and enriched their ratio to peripheral blood mononuclear cells from 1:1 to 15:1. As the only reported artificial biomaterial capable of selectively mediating the rolling of cancer cells under a physiological high-speed flow, Ca-rHA holds promise in enriching intact cells for downstream analysis in the clinics by encouraging the surface-cell contacts. STATEMENT OF SIGNIFICANCE: The development of materials that selectively mediate the rolling of cancer cells is important for the high-throughput enrichment of cancer cells rolling under high-speed flow, yet is less reported. To selectively promote the rolling of cancer stem cell marker CD44-high cancer cells, a surface with dense and stretched low molecular weight hyaluronic acid (HA_9.6k) was constructed. With Ca²⁺ regulation, HA_9.6k chains shrank to achieve the highest reported grafting density of 2.73 ± 0.20 × 10⁴ chains μm^-2 and further switched to a highly stretched conformation after the removal of Ca²⁺ ions. As the only reported artificial biomaterial capable of selectively mediating the rolling of cancer cells under a physiological high-speed flow, this Ca²⁺-regulated HA_9.6k surface holds promise in enriching intact cells for downstream analysis in the clinics.

The HER family as therapeutic targets in colorectal cancer

The human epidermal growth factor receptor (HER, ErbB) family has four members, epidermal growth factor receptor (EGFR), HER2, HER3, and HER4. Although distinct in ligands and functions, all of the HER family members are receptor tyrosine kinases playing important roles in the pathogenesis of cancers. In the era of precision medicine, the HER family is one of the most important and successful cancer therapeutic targets, hallmarked by the approval of anti-EGFR therapies for the treatment of colorectal cancer and non-small cell lung cancer, and anti-HER2 therapies for the treatment of breast cancer and gastric cancer. This review briefly discusses how HER family members were discovered, their functions and roles in cancer, and most importantly, the developmental history and recent updates of therapies targeting HER family members, with colorectal cancer as a focus. We also discussed the patient selection and drug resistance to anti-EGFR therapies in the treatment of colorectal cancer.

Resistance to anti-EGFR therapies in metastatic colorectal cancer: underlying mechanisms and reversal strategies

Cetuximab and panitumumab are monoclonal antibodies (mAbs) against epidermal growth factor receptor (EGFR) that are effective agents for metastatic colorectal cancer (mCRC). Cetuximab can prolong survival by 8.2 months in RAS wild-type (WT) mCRC patients. Unfortunately, resistance to targeted therapy impairs clinical use and efficiency. The mechanisms of resistance refer to intrinsic and extrinsic alterations of tumours. Multiple therapeutic strategies have been investigated extensively to overcome resistance to anti-EGFR mAbs. The intrinsic mechanisms include EGFR ligand overexpression, EGFR alteration, RAS/RAF/PI3K gene mutations, ERBB2/MET/IGF-1R activation, metabolic remodelling, microsatellite instability and autophagy. For intrinsic mechanisms, therapies mainly cover the following: new EGFR-targeted inhibitors, a combination of multitargeted inhibitors, and metabolic regulators. In addition, new cytotoxic drugs and small molecule compounds increase the efficiency of cetuximab. Extrinsic alterations mainly disrupt the tumour microenvironment, specifically immune cells, cancer-associated fibroblasts (CAFs) and angiogenesis. The directions include the modification or activation of immune cells and suppression of CAFs and anti-VEGFR agents. In this review, we focus on the mechanisms of resistance to anti-EGFR monoclonal antibodies (anti-EGFR mAbs) and discuss diverse approaches to reverse resistance to this therapy in hopes of identifying more mCRC treatment possibilities.

Germ line polymorphisms of genes involved in pluripotency transcription factors predict efficacy of cetuximab in metastatic colorectal cancer

BACKGROUND

Cancer stem cells (CSCs) are primarily maintained by a network of pluripotency transcription factors (PTFs). Given a close relationship of CSC regulation with epidermal growth factor receptor and vascular endothelial growth factor signalling, we investigated whether single-nucleotide polymorphisms (SNPs) in PTF genes are related to the efficacy of cetuximab and/or bevacizumab in patients with metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

Genomic and clinical data from three independent clinical trial cohorts were tested: cetuximab cohort (FOLFIRI/cetuximab arm in FIRE-3, n = 129), bevacizumab cohort 1 (FOLFIRI/bevacizumab arm in FIRE-3, n = 107) and bevacizumab cohort 2 (FOLFIRI/bevacizumab arm in TRIBE, n = 215). Genomic DNA extracted from blood samples was genotyped, and ten SNPs were tested for association with clinical outcomes.

RESULTS

In the cetuximab cohort, four SNPs were significantly associated with progression-free survival in univariate analysis: NANOG rs11055767 (any A allele vs C/C, hazard ratio [HR] = 0.62, 95% confidence interval [CI] = 0.42-0.94, p = 0.02), NANOG rs10744044 (any A allele vs G/G, HR = 0.59, 95% CI = 0.39-0.90, p = 0.01), NANOGP8 rs2168958 (any C allele vs A/A, HR = 2.12, 95% CI = 1.36-3.29, p < 0.001) and NANOGP8 rs2279066 (any C allele vs T/T, HR = 1.80, 95% CI = 1.06-1.68, p = 0.03). Multivariate analysis confirmed the significant associations for NANOGP8 rs2168958 and NANOGP8 rs2279066. In either bevacizumab cohort, no significant associations were observed in univariate analysis.

CONCLUSIONS

Germ line polymorphisms in the PTF genes could be predictive markers for cetuximab in mCRC.

Target specific tight junction modulators

Intercellular tight junctions represent a formidable barrier against paracellular drug absorption at epithelia (e.g., nasal, intestinal) and the endothelium (e.g., blood-brain barrier). In order to enhance paracellular transport of drugs and increase their bioavailability and organ deposition, active excipients modulating tight junctions have been applied. First-generation of permeation enhancers (PEs) acted by unspecific interactions, while recently developed PEs address specific physiological mechanisms. Such target specific tight junction modulators (TJMs) have the advantage of a defined specific mechanism of action. To date, merely a few of these novel active excipients has entered into clinical trials, as their lack in safety and efficiency in vivo often impedes their commercialisation. A stronger focus on the development of such active excipients would result in an economic and therapeutic improvement of current and future drugs.

The Real-Life Data of BRAF Mutation on the Treatment of Colorectal Cancer: a TOG Study

PURPOSE

Colorectal cancer is the third leading diagnosis accounting for nearly 10% of all new cancers worldwide. The distinct features among BRAF mutant colorectal cancers make these tumor groups hard to treat for oncologists. The median overall survival (OS) of these types of cancers is reported to be 9 to 14 months.

METHODS

The study was declared on the Turkish Oncology Study Group Conference and approved. The patients' data was received from the centers who confirmed to participate. The BRAF-mutated patients were included in the study. The demographic features (age, gender, etc.), type of mutation, tumor localizations, histology, microsatellite instability (MSI) status, metastasis patterns chemotherapeutic agents and progression, and death times were recorded.

RESULTS

Thirty-nine patients were enrolled in the study. Sixteen patients had concurrent KRAS mutations, while 7 had NRAS mutations. Most of the patients received doublet chemotherapies in combination with anti-VEGF agents in the first and second line of the treatment. There was a significant difference in OS according to the stage which showed a decreased survival in stage IV patients at the time of diagnosis. Concurrent KRAS mutation resulted in increased OS. The median OS was 47 and 24 months favoring the KRAS mutant group. The patients whose primary tumor operated had better survival when compared with other patients. The median OS of the operated group was 47 months, while the non-operated group was 24 months. Liver metastasis was related to worse prognosis at the time of diagnosis in univariate analysis.

CONCLUSION

In our study we found a high concurrent RAS mutation ratio in a BRAF mutant patient group which was different from prior studies. The concurrent mutations resulted in a favorable outcome in terms of OS which is also different from the current knowledge. More prospective studies are needed especially BRAF-mutated patient population and especially with concurrent RAS mutations.

Monoclonal Antibodies in Cancer Therapy

Monoclonal antibody-based immunotherapy is now considered to be a main component of cancer therapy, alongside surgery, radiation, and chemotherapy. Monoclonal antibodies possess a diverse set of clinically relevant mechanisms of action. In addition, antibodies can directly target tumor cells while simultaneously promoting the induction of long-lasting anti-tumor immune responses. The multifaceted properties of antibodies as a therapeutic platform have led to the development of new cancer treatment strategies that will have major impacts on cancer care. This review focuses on the known mechanisms of action, current clinical applications for the treatment of cancer, and mechanisms of resistance of monoclonal antibody therapy. We further discuss how monoclonal antibody-based strategies have moved towards enhancing anti-tumor immune responses by targeting immune cells instead of tumor antigens as well as some of the current combination therapies.

Structure-based Design of JOC-x, a Conjugatable Tumor Tight Junction Opener to Enhance Cancer Therapy

Disorganized intercellular junctions are critical for maintaining the integrity of solid epithelial tumors and prevent the infiltration of oncological therapies into the bulk of the malignancy. We have developed small, recombinant proteins which bind a critical junction protein, desmoglein 2, triggering the transient and specific opening of tumor tight junctions allowing for infiltration of the tumor with immune cells, oncolytic viruses, drugs, and other therapeutics. Our new molecule, JOC-x, is a promising candidate for a new class of tumor-targeting agents that accumulate both around and within tumors and remodel the tumor microenvironment. Native cysteines were removed from the parental protein, JO-4, followed by addition of a single cysteine to allow for convenient attachment of various payloads that can be targeted directly to the tumor. Our tumor-targeting protein exhibits high avidity, minimal aggregation, and is easily purified at good yields from E. coli. For proof of concept, we demonstrate effective conjugation to biotin as a model for flexible co-targeting, addition of metal ion chelators as models for imaging and radiotherapy, and linkage of the TLR3 agonist poly(I:C) as a model immune-oncologic agent. This second-generation cancer co-therapeutic protein is optimized for activity and primed for cGMP manufacture in preparation for upcoming clinical studies.

Systems analysis identifies potential target genes to overcome cetuximab resistance in colorectal cancer cells

Cetuximab (CTX), a monoclonal antibody against epidermal growth factor receptor, is being widely used for colorectal cancer (CRC) with wild-type (WT) KRAS. However, its responsiveness is still very limited and WT KRAS is not enough to indicate such responsiveness. Here, by analyzing the gene expression data of CRC patients treated with CTX monotherapy, we have identified DUSP4, ETV5, GNB5, NT5E, and PHLDA1 as potential targets to overcome CTX resistance. We found that knockdown of any of these five genes can increase CTX sensitivity in KRAS WT cells. Interestingly, we further found that GNB5 knockdown can increase CTX sensitivity even for KRAS mutant cells. We unraveled that GNB5 overexpression contributes to CTX resistance by modulating the Akt signaling pathway from experiments and mathematical simulation. Overall, these results indicate that GNB5 might be a promising target for combination therapy with CTX irrespective of KRAS mutation.

Impact of BRAF and RAS mutations on first-line efficacy of FOLFIRI plus cetuximab versus FOLFIRI plus bevacizumab: analysis of the FIRE-3 (AIO KRK-0306) study

BACKGROUND

RAS and BRAF mutations have been identified as negative prognostic factors in metastatic colorectal cancer. Efficacy of 5-fluorouracil, leucovorin, irinotecan (FOLFIRI) plus bevacizumab in patients with RAS-mutant tumours needs to be further evaluated. Whether to treat patients with BRAF-mutant tumours with either bevacizumab or anti-epidermal growth factor receptor (EGFR) antibodies remains unclear.

METHODS

Patients treated within the FIRE-3 trial were retrospectively tested for BRAF and RAS mutations using formalin fixated paraffin embedded (FFPE) tumour material applying pyrosequencing for KRAS and NRAS exon 2, 3 and 4 mutations as far as for BRAF mutations. Survival analysis was done using Kaplan-Meier estimation and differences were expressed using the log-rank test. Overall response rate (ORR) was compared using Fisher's exact test. Data from a central independent radiological response evaluation were used to calculate early tumour shrinkage (ETS) and depth of response (DpR).

RESULTS

Overall, 188 patients with RAS-mutant tumours and 48 with BRAF-mutant tumours were identified. In BRAF-mutant patients, ORR was numerically higher in the cetuximab versus the bevacizumab arm (52% versus 40%), while comparable results were achieved for progression-free survival (PFS; hazard ratio [HR] = 0.84, p = 0.56) and overall survival (OS; HR 0.79, p = 0.45). RAS mutation was associated with a trend towards lower ORR (37% versus 50.5%, p = 0.11) and shorter PFS (7.4 versus 9.7 months; HR 1.25; p = 0.14) in patients receiving FOLFIRI plus cetuximab versus bevacizumab, but OS was comparable (19.1 versus 20.1 months; HR 1.05; p = 0.73), respectively. ETS identified subgroups sensitive to cetuximab-based treatment in both BRAF- (9/17) and RAS-mutant (18/48) patients and was associated with significantly longer OS. DpR was comparable between both treatment arms in RAS- and BRAF-mutant patients, respectively.

CONCLUSIONS

In BRAF- and RAS-mutant patients, cetuximab- and bevacizumab-based treatment had comparable survival times. ETS represents an early parameter associated with the benefit from anti-EGFR, while this was not the case with vascular endothelial growth factor A blockade.

Consensus molecular subtypes and the evolution of precision medicine in colorectal cancer

Critical driver genomic events in colorectal cancer have been shown to affect the response to targeted agents that were initially developed under the 'one gene, one drug' paradigm of precision medicine. Our current knowledge of the complexity of the cancer genome, clonal evolution patterns under treatment pressure and pharmacodynamic effects of target inhibition support the transition from a one gene, one drug approach to a 'multi-gene, multi-drug' model when making therapeutic decisions. Better characterization of the transcriptomic subtypes of colorectal cancer, encompassing tumour, stromal and immune components, has revealed convergent pathway dependencies that mandate a 'multi-molecular' perspective for the development of therapies to treat this disease.

Metalloprotease-disintegrin ADAM12 actively promotes the stem cell-like phenotype in claudin-low breast cancer

BACKGROUND

ADAM12 is upregulated in human breast cancers and is a predictor of chemoresistance in estrogen receptor-negative tumors. ADAM12 is induced during epithelial-to-mesenchymal transition, a feature associated with claudin-low breast tumors, which are enriched in cancer stem cell (CSC) markers. It is currently unknown whether ADAM12 plays an active role in promoting the CSC phenotype in breast cancer cells.

METHODS

ADAM12 expression was downregulated in representative claudin-low breast cancer cell lines, SUM159PT and Hs578T, using siRNA transfection or inducible shRNA expression. Cell characteristics commonly associated with the CSC phenotype in vitro (cell migration, invasion, anoikis resistance, mammosphere formation, ALDH activity, and expression of the CD44 and CD24 cell surface markers) and in vivo (tumor formation in mice using limiting dilution transplantation assays) were evaluated. RNA sequencing was performed to identify global gene expression changes after ADAM12 knockdown.

RESULTS

We found that sorted SUM159PT cell populations with high ADAM12 levels had elevated expression of CSC markers and an increased ability to form mammospheres. ADAM12 knockdown reduced cell migration and invasion, decreased anoikis resistance, and compromised mammosphere formation. ADAM12 knockdown also diminished ALDEFLUOR⁺ and CD44^hi/CD24^-/lo CSC-enriched populations in vitro and reduced tumorigenesis in mice in vivo. RNA sequencing identified a significant overlap between ADAM12- and Epidermal Growth Factor Receptor (EGFR)-regulated genes. Consequently, ADAM12 knockdown lowered the basal activation level of EGFR, and this effect was abolished by batimastat, a metalloproteinase inhibitor. Furthermore, incubation of cells with exogenously added EGF prevented the downregulation of CD44^hi/CD24^-/lo cell population by ADAM12 knockdown.

CONCLUSIONS

These results indicate that ADAM12 actively supports the CSC phenotype in claudin-low breast cancer cells via modulation of the EGFR pathway.

Systems pharmacology and enhanced pharmacodynamic models for understanding antibody-based drug action and toxicity

Pharmacokinetic (PK) and pharmacodynamic (PD) models seek to describe the temporal pattern of drug exposures and their associated pharmacological effects produced at micro- and macro-scales of organization. Antibody-based drugs have been developed for a large variety of diseases, with effects exhibited through a comprehensive range of mechanisms of action. Mechanism-based PK/PD and systems pharmacology models can play a major role in elucidating and integrating complex antibody pharmacological properties, such as nonlinear disposition and dynamical intracellular signaling pathways triggered by ligation to their cognate targets. Such complexities can be addressed through the use of robust computational modeling techniques that have proven powerful tools for pragmatic characterization of experimental data and for theoretical exploration of antibody efficacy and adverse effects. The primary objectives of such multi-scale mathematical models are to generate and test competing hypotheses and to predict clinical outcomes. In this review, relevant systems pharmacology and enhanced PD (ePD) models that are used as predictive tools for antibody-based drug action are reported. Their common conceptual features are highlighted, along with approaches used for modeling preclinical and clinically available data. Key examples illustrate how systems pharmacology and ePD models codify the interplay among complex biology, drug concentrations, and pharmacological effects. New hybrid modeling concepts that bridge cutting-edge systems pharmacology models with established PK/ePD models will be needed to anticipate antibody effects on disease in subpopulations and individual patients.

Epithelial Junction Opener Improves Oncolytic Adenovirus Therapy in Mouse Tumor Models

A central resistance mechanism in solid tumors is the maintenance of epithelial junctions between malignant cells that prevent drug penetration into the tumor. Human adenoviruses (Ads) have evolved mechanisms to breach epithelial barriers. For example, during Ad serotype 3 (Ad3) infection of epithelial tumor cells, massive amounts of subviral penton-dodecahedral particles (PtDd) are produced and released from infected cells to trigger the transient opening of epithelial junctions, thus facilitating lateral virus spread. We show here that an Ad3 mutant that is disabled for PtDd production is significantly less effective in killing of epithelial human xenograft tumors than the wild-type Ad3 virus. Intratumoral spread and therapeutic effect of the Ad3 mutant was enhanced by co-administration of a small recombinant protein (JO; produced in Escherichia coli) that incorporated the minimal junction opening domains of PtDd. We then demonstrated that co-administration of JO with replication-competent Ads that do not produce PtDd (Ad5, Ad35) resulted in greater attenuation of tumor growth than virus injection alone. Furthermore, we genetically modified a conditionally replicating Ad5-based oncolytic Ad (Ad5Δ24) to express a secreted form of JO upon replication in tumor cells. The JO-expressing virus had a significantly greater antitumor effect than the unmodified AdΔ24 version. Our findings indicate that epithelial junctions limit the efficacy of oncolytic Ads and that this problem can be address by co-injection or expression of JO. JO has also the potential for improving cancer therapy with other types of oncolytic viruses.

Prognostic Impact of Primary Tumor Location on Clinical Outcomes of Metastatic Colorectal Cancer Treated With Cetuximab Plus Oxaliplatin-Based Chemotherapy: A Subgroup Analysis of the JACCRO CC-05/06 Trials

INTRODUCTION

Primary tumor location is a critical prognostic factor in metastatic colorectal cancer (mCRC); however, it remains unclear whether tumor location is a predictor of the response to cetuximab treatment. It is also uncertain if BRAF mutation contributes to the impact of tumor location on survival. We assessed the prognostic impact of tumor location on clinical outcomes in mCRC patients treated with first-line cetuximab chemotherapy.

PATIENTS AND METHODS

The associations of tumor location with overall survival and progression-free survival were evaluated in mCRC patients with KRAS exon 2 wild-type tumors who were enrolled onto 2 clinical trials: JACCRO CC-05 of cetuximab plus FOLFOX (n = 57, UMIN000004197) and CC-06 of cetuximab plus SOX (n = 61, UMIN000007022). Tumors proximal or from splenic flexure to rectum were defined as right-sided or left-sided, respectively. In addition, exploratory RAS and BRAF mutation analyses were performed.

RESULTS

A total of 110 patients were assessable for tumor location; 90 had left-sided tumors. Left-sided tumors were significantly associated with longer overall survival (36.2 vs. 12.6 months, hazard ratio = 0.28, P < .0001) and progression-free survival (11.1 vs. 5.6 months, hazard ratio = 0.47, P = .0041) than right-sided tumors; similar results were obtained in multivariate analysis. A subanalysis showed that the association was evident in the FOLFOX group and that tumor location was an independent prognostic factor irrespective of BRAF status in RAS wild-type patients.

CONCLUSION

Primary tumor location might be a predictor of survival independent of BRAF status in mCRC patients who receive first-line cetuximab combined with oxaliplatin-based chemotherapy.

Combined assessment of EGFR-related molecules to predict outcome of 1st-line cetuximab-containing chemotherapy for metastatic colorectal cancer

Several studies have reported that epidermal growth factor receptor (EGFR)-related molecules may serve as predictors of cetuximab treatment for metastatic colorectal cancer (mCRC), such as EGFR gene copy number (GCN), expression of 2 ligands of EGFR, amphiregulin (AREG) and epiregulin (EREG), and EGFR CA simple sequence repeat 1 (CA-SSR1) polymorphism; however, these biomarkers still remain not useful in clinical practice since they have been evaluated using cohorts with patients treated in various settings of chemotherapy. We therefore analyzed associations of mRNA expression of AREG and EREG, EGFR GCN, and CA-SSR1 polymorphism [short (S;≤ 19) / long (L; ≥ 20)] with clinical outcomes in 77 Japanese patients with KRAS exon 2 wild-type mCRC enrolled in phase II trials of FOLFOX (n = 28/57, UMIN000004197) or SOX (n = 49/67, UMIN000007022) plus cetuximab as first-line therapy. High AREG expression correlated with significantly better progression-free survival (median 11.6 vs. 66 months, HR 0.52, P = 0.037); moreover, it remained statistically significant in multivariate analysis (HR: 0.48, P = 0.027). S/S genotype of CA-SSR1 predicted severe skin toxicity (P = 0.040). Patients with both AREG-low and EGFR low-GCN had significantly shorter overall survival than the others (median 22.2 vs. 42.8 months, HR 2.34, P = 0.042). The multivariate analysis showed that molecular status with both AREG-low and EGFR low-GCN was a predictor of worse survival (P = 0.006). In conclusion, AREG mRNA expression and EGFR CA-SSR1 polymorphism predict survival and skin toxicity, respectively, of initial chemotherapy with cetuximab. Our results also suggest potential prognostic value of the combined assessment of AREG and EGFR GCN for first-line cetuximab treatment.

Preclinical safety and efficacy studies with an affinity-enhanced epithelial junction opener and PEGylated liposomal doxorubicin

A central treatment resistance mechanism in solid tumors is the maintenance of epithelial junctions between malignant cells that prevent drug penetration into the tumor. We have developed a small recombinant protein (JO-1) that triggers the transient opening of intercellular junctions and thus increases the efficacy of monoclonal antibodies and chemotherapeutic drugs without causing toxicity in mouse tumor models. Here, we provide data toward the clinical translation of an affinity-enhanced version of JO-1, which we call JO-4, in combination with PEGylated liposomal doxorubicin (PLD)/Doxil for ovarian cancer therapy. We have presented X-ray crystallography data suggesting a structural basis for the higher affinity of JO-4 to DSG2. We also confirmed JO-4 efficacy in a xenograft model with primary ovarian cancer cells showing that JO-4 can salvage Doxil therapy when given at a dose that was threefold lower than the therapeutic dose. Furthermore, we tested the safety of intravenous JO-4 alone and in combination with Doxil in Macaca fascicularis, an adequate animal model for predicting toxicity in humans. Our studies did not show critical JO-4-related toxicity or an increase of Doxil-related side effects. Our efficacy and safety data will help to support an Investigational new drug-filing for a JO-4/Doxil combination treatment.

Gene expression profiling for targeted cancer treatment

INTRODUCTION

There is certain degree of frustration and discontent in the area of microarray gene expression data analysis of cancer datasets. It arises from the mathematical problem called 'curse of dimensionality,' which is due to the small number of samples available in training sets, used for calculating transcriptional signatures from the large number of differentially expressed (DE) genes, measured by microarrays. The new generation of causal reasoning algorithms can provide solutions to the curse of dimensionality by transforming microarray data into activity of a small number of cancer hallmark pathways. This new approach can make feature space dimensionality optimal for mathematical signature calculations.

AREAS COVERED

The author reviews the reasons behind the current frustration with transcriptional signatures derived from DE genes in cancer. He also provides an overview of the novel methods for signature calculations based on differentially variable genes and expression regulators. Furthermore, the authors provide perspectives on causal reasoning algorithms that use prior knowledge about regulatory events described in scientific literature to identify expression regulators responsible for the differential expression observed in cancer samples.

EXPERT OPINION

The author advocates causal reasoning methods to calculate cancer pathway activity signatures. The current challenge for these algorithms is in ensuring quality of the knowledgebase. Indeed, the development of cancer hallmark pathway collections, together with statistical algorithms to transform activity of expression regulators into pathway activity, are necessary for causal reasoning to be used in cancer research.

Overcoming physical barriers in cancer therapy

Most solid tumors are of epithelial origin and, although malignant cells are de-differentiated, they maintain intercellular junctions, a key feature of epithelial cells, both in the primary tumor as well as in metastatic lesions. These intercellular junctions represent a protective mechanism against attacks by the host’s immune system and pose as physical barriers that prevent intratumoral penetration and dissemination of cancer therapeutics. A key protein of epithelial junctions is desmoglein 2 (DSG2). DSG2 is consistently upregulated in all cancers analyzed. Recently, we demonstrated that a group of human adenoviruses (Ad serotypes 3, 7, 11 and 14) use DSG2 as a primary attachment receptor for the infection of cells. We subsequently created a small recombinant protein derived from Ad serotype 3, which binds to DSG2 and triggers transient opening of epithelial intercellular junctions. We named the protein “JO-1” (“junction opener -1”). JO-1 is a small protein that can easily be produced in E. coli. JO-1 binding to and clustering of DSG2 triggers an epithelial-to-mesenchymal-transition that results in transient opening of epithelial junctions. We have shown in over 25 xenograft tumor models that the intravenous injection of JO-1 increased the efficacy of monoclonal and chemotherapy, subsequently reducing the required treatment dose and concomitantly reducing the toxic side effect of these treatments. The application of JO-1 has not been associated with toxicities in safety studies performed in human DSG2-transgenic mice and monkeys.

Intestinal stem cells and the colorectal cancer microenvironment

Colorectal cancer (CRC) remains a highly fatal condition in part due to its resilience to treatment and its propensity to spread beyond the site of primary occurrence. One possible avenue for cancer to escape eradication is via stem-like cancer cells that, through phenotypic heterogeneity, are more resilient than other tumor constituents and are key contributors to cancer growth and metastasis. These proliferative tumor cells are theorized to possess many properties akin to normal intestinal stem cells. Not only do these CRC “stem” cells demonstrate similar restorative ability, they also share many cell pathways and surface markers in common, as well as respond to the same key niche stimuli. With the improvement of techniques for epithelial stem cell identification, our understanding of CRC behavior is also evolving. Emerging evidence about cellular plasticity and epithelial mesenchymal transition are shedding light onto metastatic CRC processes and are also challenging fundamental concepts about unidirectional epithelial proliferation. This review aims to reappraise evidence supporting the existence and behavior of CRC stem cells, their relationship to normal stem cells, and their possible dependence on the stem cell niche.

Qualitative changes in the proteome of extracellular vesicles accompanying cancer cell transition to mesenchymal state

Transitions of the cancer cell phenotype between epithelial and mesenchymal states (EMT) are likely to alter the patterns of intercellular communication. In this regard we have previously documented that EMT-like changes trigger quantitative rearrangements in exosomal vesicle emission in A431 cancer cells driven by oncogenic epidermal growth factor receptor (EGFR). Here we report that extracellular vesicles (EVs) produced by these cancer cells in their epithelial and mesenchymal states exhibit profound qualitative differences in their proteome. Thus, induction of the EMT-like state through blockade of E-cadherin and EGFR stimulation provoked a mesenchymal shift in cellular morphology and enrichment in the CD44-high/CD24-low immunophenotype, often linked to cellular stemness. This change also resulted in reprogramming of the EV-related proteome (distinct from that of corresponding cells), which contained 30 unique protein signals, and revealed enrichment in pathways related to cellular growth, cell-to-cell signaling, and cell movement. Some of the most prominent EV-related proteins were validated, including integrin α2 and tetraspanin CD9. We propose that changes in cellular differentiation status translate into unique qualitative rearrangements in the cargo of EVs, a process that may have implications for intercellular communication and could serve as source of new biomarkers to detect EMT-like processes in cancer.

Strategies to increase drug penetration in solid tumors

Despite significant improvement in modalities for treatment of cancer that led to a longer survival period, the death rate of patients with solid tumors has not changed during the last decades. Emerging studies have identified several physical barriers that limit the therapeutic efficacy of cancer therapeutic agents such as monoclonal antibodies, chemotherapeutic agents, anti-tumor immune cells, and gene therapeutics. Most solid tumors are of epithelial origin and, although malignant cells are de-differentiated, they maintain intercellular junctions, a key feature of epithelial cells, both in the primary tumor as well as in metastatic lesions. Furthermore, nests of malignant epithelial tumor cells are shielded by layers of extracellular matrix (ECM) proteins (e.g., collagen, elastin, fibronectin, laminin) whereby tumor vasculature rarely penetrates into the tumor nests. In this chapter, we will review potential strategies to modulate the ECM and epithelial junctions to enhance the intratumoral diffusion and/or to remove physical masking of target receptors on malignant cells. We will focus on peptides that bind to the junction protein desmoglein 2 and trigger intracellular signaling, resulting in the transient opening of intercellular junctions. Intravenous injection of these junction openers increased the efficacy and safety of therapies with monoclonal antibodies, chemotherapeutics, and T cells in mouse tumor models and was safe in non-human primates. Furthermore, we will summarize approaches to transiently degrade ECM proteins or downregulate their expression. Among these approaches is the intratumoral expression of relaxin or decorin after adenovirus- or stem cell-mediated gene transfer. We will provide examples that relaxin-based approaches increase the anti-tumor efficacy of oncolytic viruses, monoclonal antibodies, and T cells.

Anti-epidermal growth factor receptor therapy in head and neck squamous cell carcinoma: focus on potential molecular mechanisms of drug resistance

Targeted therapy against the epidermal growth factor receptor (EGFR) is one of the most promising molecular therapeutics for head and neck squamous cell carcinoma (HNSCC). EGFR is overexpressed in a wide range of malignancies, including HNSCC, and initiates important signal transduction pathways in HNSCC carcinogenesis. However, primary and acquired resistance are serious problems and are responsible for low single-agent response rate and tumor recurrence. Therefore, an improved understanding of the molecular mechanisms of resistance to EGFR inhibitors may provide valuable indications to identify biomarkers that can be used clinically to predict response to EGFR blockade and to establish new treatment options to overcome resistance. To date, no predictive biomarker for HNSCC is available in the clinic. Therapeutic resistance to anti-EGFR therapy may arise from mechanisms that can compensate for reduced EGFR signaling and/or mechanisms that can modulate EGFR-dependent signaling. In this review, we will summarize some of these molecular mechanisms and describe strategies to overcome that resistance.

EMT-activating transcription factors in cancer: beyond EMT and tumor invasiveness

Cancer is a complex multistep process involving genetic and epigenetic changes that eventually result in the activation of oncogenic pathways and/or inactivation of tumor suppressor signals. During cancer progression, cancer cells acquire a number of hallmarks that promote tumor growth and invasion. A crucial mechanism by which carcinoma cells enhance their invasive capacity is the dissolution of intercellular adhesions and the acquisition of a more motile mesenchymal phenotype as part of an epithelial-to-mesenchymal transition (EMT). Although many transcription factors can trigger it, the full molecular reprogramming occurring during an EMT is mainly orchestrated by three major groups of transcription factors: the ZEB, Snail and Twist families. Upregulated expression of these EMT-activating transcription factors (EMT-ATFs) promotes tumor invasiveness in cell lines and xenograft mice models and has been associated with poor clinical prognosis in human cancers. Evidence accumulated in the last few years indicates that EMT-ATFs also regulate an expanding set of cancer cell capabilities beyond tumor invasion. Thus, EMT-ATFs have been shown to cooperate in oncogenic transformation, regulate cancer cell stemness, override safeguard programs against cancer like apoptosis and senescence, determine resistance to chemotherapy and promote tumor angiogenesis. This article reviews the expanding portfolio of functions played by EMT-ATFs in cancer progression.

Targeting a novel onco-glycoprotein antigen at tumoral pancreatic cell surface by mAb16D10 induces cell death

The mAb16D10 was raised against a pathological onco-glycoform of bile salt-dependent lipase isolated from the pancreatic juice of a patient suffering from a pancreatic adenocarcinoma. We previously showed that mAb16D10 specifically discriminates human pancreatic tumor tissues from other cancer and nontumor tissues. In this study, we report that mAb16D10 inhibited the proliferation of only human pancreatic tumor cells expressing 16D10 plasma membrane Ag. Interaction of mAb16D10 with its cognate surface Ag on pancreatic cells promoted cell death by activation of the p53- and caspase-dependent apoptotic pathway, and silencing of p53 decreased cell death. The decreased proliferation was also partly due to cell cycle arrest in G1/S phase, mAb16D10 triggering of glycogen synthase kinase-3β (GSK-3β) activation, degradation of β-catenin, and decreased expression of cyclin D1. GSK-3β positively affected p53 expression in pancreatic tumor cells after mAb16D10 binding. Inhibition of GSK-3β activity reversed the effects induced by mAb16D10 in SOJ-6 cells, supporting the pivotal role of GSK-3β signaling in the mechanisms of action induced by mAb16D10. Also, mAb16D10 cell treatment led to membrane overexpression of E-cadherin. Both E-cadherin and tumor Ag were localized in membrane lipid cholesterol-rich microdomains and are thought to belong to signaling platforms involved in the induction of cell cycle arrest and cell death. Overall, this study reveals that mAb16D10 holds great potential to prevent pancreatic tumor proliferation by apoptotic cell death, thus promising therapeutic prospects for treatment of pancreatic adenocarcinoma, a highly lethal disease.

A comparison of epithelial-to-mesenchymal transition and re-epithelialization

Wound healing and cancer metastasis share a common starting point, namely, a change in the phenotype of some cells from stationary to motile. The term, epithelial-to-mesenchymal transition (EMT) describes the changes in molecular biology and cellular physiology that allow a cell to transition from a sedentary cell to a motile cell, a process that is relevant not only for cancer and regeneration, but also for normal development of multicellular organisms. The present review compares the similarities and differences in cellular response at the molecular level as tumor cells enter EMT or as keratinocytes begin the process of re-epithelialization of a wound. Looking toward clinical interventions that might modulate these processes, the mechanisms and outcomes of current and potential therapies are reviewed for both anti-cancer and pro-wound healing treatments related to the pathways that are central to EMT. Taken together, the comparison of re-epithelialization and tumor EMT serves as a starting point for the development of therapies that can selectively modulate different forms of EMT.

Cross-suppression of EGFR ligands amphiregulin and epiregulin and de-repression of FGFR3 signalling contribute to cetuximab resistance in wild-type KRAS tumour cells

BACKGROUND

In addition to the mutational status of KRAS, the epidermal growth factor receptor (EGFR) ligands amphiregulin (AREG) and epiregulin (EREG) might function as bona fide biomarkers of cetuximab (Ctx) sensitivity for most EGFR-driven carcinomas.

METHODS

Lentivirus-delivered small hairpin RNAs were employed to specifically reduce AREG or EREG gene expression in wild-type KRAS A431 squamous cell carcinoma cells. Colony-forming assays were used to monitor the impact of AREG and EREG knockdown on Ctx efficacy. Amphiregulin and EREG protein expression levels were assessed by quantitative ELISA in parental A431 cells and in pooled populations of A431 cells adapted to grow in the presence of Ctx. A phosphoproteomic platform was used to measure the relative level of phosphorylation of 42 distinct receptor tyrosine kinases before and after the acquisition of resistance to Ctx.

RESULTS

Stable gene silencing of either ligand was found to notably reduce the expression of the other ligand. Parental A431 cells with normal expression levels of AREG/EREG exhibited significantly increased growth inhibition in response to Ctx, compared with derivatives that are engineered to produce minimal AREG/EREG. The parental A431 cells acutely treated with Ctx exhibited reduced basal expression levels of AREG/EREG. Pooled populations of Ctx-resistant A431 cells expressed significantly lower levels of AREG/EREG and were insensitive to the downregulatory effects of Ctx. Phosphoproteomic screen identified a remarkable hyperactivation of FGFR3 in Ctx-resistant A431 cells, which gained sensitivity to the cytotoxic and apoptotic effects of the FGFR3 TK inhibitor PD173074. The A431 parental cells acutely treated with Ctx rapidly activated FGFR3 and their concomitant exposure to Ctx and PD173074 resulted in synergistic apoptosis.

CONCLUSION

Cross-suppression of AREG/EREG expression may explain the tight co-expression of AREG and EREG, as well as their tendency to be more highly expressed than other EGFR ligands to determine Ctx efficacy. The positive selection for Ctx-resistant tumour cells exhibiting AREG/EREG cross-suppression may have an important role in the emergence of Ctx resistance. As de-repression of FGFR3 activity rapidly replaces the loss of EGFR-ligand signalling in terms of cell proliferation and survival, combinations of Ctx and FGFR3-targeted drugs may be a valuable strategy to enhance the efficacy of single Ctx while preventing or delaying acquired resistance to Ctx.

Coadministration of epithelial junction opener JO-1 improves the efficacy and safety of chemotherapeutic drugs

PURPOSE

Epithelial junctions between tumor cells inhibit the penetration of anticancer drugs into tumors. We previously reported on recombinant adenovirus serotype 3-derived protein (JO-1), which triggers transient opening of intercellular junctions in epithelial tumors through binding to desmoglein 2 (DSG2), and enhances the antitumor effects of several therapeutic monoclonal antibodies. The goal of this study was to evaluate whether JO-1 cotherapy can also improve the efficacy of chemotherapeutic drugs.

EXPERIMENTAL DESIGN

The effect of intravenous application of JO-1 in combination with several chemotherapy drugs, including paclitaxel/Taxol, nanoparticle albumin-bound paclitaxel/Abraxane, liposomal doxorubicin/Doxil, and irinotecan/Camptosar, was tested in xenograft models for breast, colon, ovarian, gastric and lung cancer. Because JO-1 does not bind to mouse cells, for safety studies with JO-1, we also used human DSG2 (hDSG2) transgenic mice with tumors that overexpressed hDSG2.

RESULTS

JO-1 increased the efficacy of chemotherapeutic drugs, and in several models overcame drug resistance. JO-1 treatment also allowed for the reduction of drug doses required to achieve antitumor effects. Importantly, JO-1 coadmininstration protected normal tissues, including bone marrow and intestinal epithelium, against toxic effects that are normally associated with chemotherapeutic agents. Using the hDSG2-transgenic mouse model, we showed that JO-1 predominantly accumulates in tumors. Except for a mild, transient diarrhea, intravenous injection of JO-1 (2 mg/kg) had no critical side effects on other tissues or hematologic parameters in hDSG2-transgenic mice.

CONCLUSIONS

Our preliminary data suggest that JO-1 cotherapy has the potential to improve the therapeutic outcome of cancer chemotherapy.

Basal/HER2 breast carcinomas: integrating molecular taxonomy with cancer stem cell dynamics to predict primary resistance to trastuzumab (Herceptin)

High rates of inherent primary resistance to the humanized monoclonal antibody trastuzumab (Herceptin) are frequent among HER2 gene-amplified breast carcinomas in both metastatic and adjuvant settings. The clinical efficacy of trastuzumab is highly correlated with its ability to specifically and efficiently target HER2-driven populations of breast cancer stem cells (CSCs). Intriguingly, many of the possible mechanisms by which cancer cells escape trastuzumab involve many of the same biomarkers that have been implicated in the biology of CS-like tumor-initiating cells. In the traditional, one-way hierarchy of CSCs in which all cancer cells descend from special self-renewing CSCs, HER2-positive CSCs can occur solely by self-renewal. Therefore, by targeting CSC self-renewal and resistance, trastuzumab is expected to induce tumor shrinkage and further reduce breast cancer recurrence rates when used alongside traditional therapies. In a new, alternate model, more differentiated non-stem cancer cells can revert to trastuzumab-refractory, CS-like cells via the activation of intrinsic or microenvironmental paths-to-stemness, such as the epithelial-to-mesenchymal transition (EMT). Alternatively, stochastic transitions of trastuzumab-responsive CSCs might also give rise to non-CSC cellular states that lack major attributes of CSCs and, therefore, can remain "hidden" from trastuzumab activity. Here, we hypothesize that a better understanding of the CSC/non-CSC social structure within HER2-overexpressing breast carcinomas is critical for trastuzumab-based treatment decisions in the clinic. First, we decipher the biological significance of CSC features and the EMT on the molecular effects and efficacy of trastuzumab in HER2-positive breast cancer cells. Second, we reinterpret the genetic heterogeneity that differentiates trastuzumab-responders from non-responders in terms of CSC cellular states. Finally, we propose that novel predictive approaches aimed at better forecasting early tumor responses to trastuzumab should identify biological determinants that causally underlie the intrinsic flexibility of HER2-positive CSCs to "enter" into or "exit" from trastuzumab-sensitive states. An accurate integration of CSC cellular states and EMT-related biomarkers with the currently available breast cancer molecular taxonomy may significantly improve our ability to make a priori decisions about whether patients belonging to HER2 subtypes differentially enriched with a "mesenchymal transition signature" (e.g., luminal/HER2 vs. basal/HER2) would distinctly benefit from trastuzumab-based therapy ab initio.

Epithelial junction opener JO-1 improves monoclonal antibody therapy of cancer

The efficacy of monoclonal antibodies (mAb) used to treat solid tumors is limited by intercellular junctions which tightly link epithelial tumor cells to each another. In this study, we define a small, recombinant adenovirus serotype 3-derived protein, termed junction opener 1 (JO-1), which binds to the epithelial junction protein desmoglein 2 (DSG2). In mouse xenograft models employing Her2/neu- and EGFR-positive human cancer cell lines, JO-1 mediated cleavage of DSG2 dimers and activated intracellular signaling pathways which reduced E-cadherin expression in tight junctions. Notably, JO-1-triggered changes allowed for increased intratumoral penetration of the anti-Her2/neu mAb trastuzumab (Herceptin) and improved access to its target receptor, Her2/neu, which is partly trapped in tight junctions. This effect translated directly into increased therapeutic efficacy of trastuzumab in mouse xenograft models using breast, gastric, and ovarian cancer cells that were Her2/neu-positive. Furthermore, combining JO-1 with the EGFR-targeting mAb cetuximab (Erbitux) greatly improved therapeutic outcomes in a metastatic model of EGFR-positive lung cancer. A combination of JO-1 with an approach that triggered transient degradation of tumor stroma proteins elicited eradication of tumors. Taken together, our findings offer preclinical proof of concept to employ JO-1 in combination with mAb therapy.

Antitumour efficacy of MEK inhibitors in human lung cancer cells and their derivatives with acquired resistance to different tyrosine kinase inhibitors

Background:

To study the molecular mechanisms regulating cancer cell resistance to four different tyrosine kinase inhibitors (TKIs): erlotinib, gefitinib, vandetanib and sorafenib.

Methods:

An in vitro model of acquired resistance to these TKIs was developed by continuously treating the human lung adenocarcinoma cell line CALU-3 with escalating doses of each drug. Transcriptional profiling was performed with Agilent whole genome microarrays. Western blot analysis, enzyme-linked immunosorbent (ELISA), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell proliferation, migration, invasion and anchorage-independent colony growth assays were conducted in vitro and experiments with established xenografts in athymic nude mice were performed in vivo in parental (P) and TKI-resistant (R) CALU-3 cell lines.

Results:

As compared with P-CALU-3 cells, in TKI-R CALU-3 cell lines a significant increase in the expression of activated, phosphorylated MET, IGF-1R, AKT, MEK, MAPK and of survivin was observed. Downregulation of E-cadherin and amphiregulin mRNAs and upregulation of vimentin, VE-cadherin, HIF-1α and vascular endothelial growth factor receptor-1 mRNAs were observed in all four TKI-R CALU-3 cell lines. All four TKI-R CALU-3 cells showed increased invasion, migration and anchorage-independent growth. Together, these data suggest epithelial to mesenchymal transition (EMT) in TKI-R CALU-3 cells. Treatment with several agents that target AKT, MET or IGF-1R did not affect TKI-R CALU-3 cell proliferation. In contrast, treatment with MSC19363669B and selumetinib, two selective MEK inhibitors, caused inhibition of cell proliferation, invasion, migration, anchorage-independent growth in vitro and of tumour growth in vivo of all four TKI-R CALU-3 cell lines.

Conclusion:

These data suggest that resistance to four different TKIs is characterised by EMT, which is MEK-inhibitor sensitive in human CALU-3 lung adenocarcinoma.