Characterization of DNA topoisomerase I in three SN-38 resistant human colon cancer cell lines reveals a new pair of resistance-associated mutations

A new TROP2-targeting antibody-drug conjugate shows potent antitumor efficacy in breast and lung cancers

Trophoblast cell surface antigen 2 (Trop2) is considered to be an attractive therapeutic target in cancer treatments. We previously generated a new humanized anti-Trop2 antibody named hIMB1636, and designated it as an ideal targeting carrier for cancer therapy. Lidamycin (LDM) is a new antitumor antibiotic, containing an active enediyne chromophore (AE) and a noncovalently bound apoprotein (LDP). AE and LDP can be separated and reassembled, and the reassembled LDM possesses cytotoxicity similar to that of native LDM; this has made LDM attractive in the preparation of gene-engineering drugs. We herein firstly prepared a new fusion protein hIMB1636-LDP composed of hIMB1636 and LDP by genetic engineering. This construct showed potent binding activities to recombinant antigen with a KD value of 4.57 nM, exhibited binding to Trop2-positive cancer cells and internalization and transport to lysosomes, and demonstrated powerful tumor-targeting ability in vivo. We then obtained the antibody-drug conjugate (ADC) hIMB1636-LDP-AE by molecular reconstitution. In vitro, hIMB1636-LDP-AE inhibited the proliferation, migration, and tumorsphere formation of tumor cells with half-maximal inhibitory concentration (IC50) values at the sub-nanomolar level. Mechanistically, hIMB1636-LDP-AE induced apoptosis and cell-cycle arrest. In vivo, hIMB1636-LDP-AE also inhibited the growth of breast and lung cancers in xenograft models. Moreover, compared to sacituzumab govitecan, hIMB1636-LDP-AE showed more potent antitumor activity and significantly lower myelotoxicity in tumors with moderate Trop2 expression. This study fully revealed the potent antitumor efficacy of hIMB1636-LDP-AE, and also provided a new preparation method for LDM-based ADC, as well as a promising candidate for breast cancer and lung cancer therapeutics.

Could a Long-Acting Prodrug of SN-38 be Efficacious in Sacituzumab Govitecan-Resistant Tumors?

We previously proposed that sacituzumab govitecan (SG, Trodelvy®) likely acts as a simple prodrug of systemic SN-38 as well as an antibody drug conjugate (ADC). In the present commentary, we assess whether a long-acting SN-38 prodrug, such as PLX038, might be efficacious in SG-resistant patients. We first describe possible mechanisms of action of SG, with new insights on pharmacokinetics and TROP2 receptor occupancy. We argue that SG is not an optimal conventional ADC and that the amount of systemic SN-38 spontaneously hydrolyzed from the ADC is so high it must have activity. Then, we describe the concept of time-over-target as related to the pharmacology of SG and PLX038 as SN-38 prodrugs. To be clear, we are not in any way suggesting that PLX038 or any SN-38 prodrug is superior to SG as an anticancer agent. Clearly, SG has the benefit over antigen-independent SN-38 prodrugs in that it targets cells with the TROP2 receptor. However, we surmise that PLX038 should be a more efficacious and less toxic prodrug of systemic SN-38 than SG. Finally, we suggest possible mechanisms of SG resistance and how PLX038 might perform in the context of each. Taken together, we argue that-contrary to many opinions-SG does not exclusively act as a conventional ADC, and propose that PLX038 may be efficacious in some settings of SG-resistance.

Design and synthesis of multivalent drug delivery system with CA IX inhibitors as ligands

A multivalent ligand delivery system holds tremendous potential in the field of tumor-targeted drug delivery. It addresses the challenges posed by the low affinity between small molecule ligand receptors and the rapid metabolism of small molecule drug conjugates (SMDCs) in vivo. Notably, existing multivalent ligand systems have demonstrated significant anti-tumor activity in various tumor models. In this study, we have developed a novel multivalent ligand delivery system for SN38, utilizing acetazolamide, a carbonic anhydrase IX (CA IX) inhibitor, as the target ligand. Our multivalent ligand delivery systems exhibited superior metabolic stability and enhanced targeting specificity compared to SMDC molecules. Furthermore, they demonstrated improved anti-proliferation activity, addressing the existing challenges associated with the low receptor affinity and rapid metabolism of SMDCs.

Resistance to TOP-1 Inhibitors: Good Old Drugs Still Can Surprise Us

Irinotecan (SN-38) is a potent and broad-spectrum anticancer drug that targets DNA topoisomerase I (Top1). It exerts its cytotoxic effects by binding to the Top1-DNA complex and preventing the re-ligation of the DNA strand, leading to the formation of lethal DNA breaks. Following the initial response to irinotecan, secondary resistance is acquired relatively rapidly, compromising its efficacy. There are several mechanisms contributing to the resistance, which affect the irinotecan metabolism or the target protein. In addition, we have demonstrated a major resistance mechanism associated with the elimination of hundreds of thousands of Top1 binding sites on DNA that can arise from the repair of prior Top1-dependent DNA cleavages. Here, we outline the major mechanisms of irinotecan resistance and highlight recent advancements in the field. We discuss the impact of resistance mechanisms on clinical outcomes and the potential strategies to overcome resistance to irinotecan. The elucidation of the underlying mechanisms of irinotecan resistance can provide valuable insights for the development of effective therapeutic strategies.

Rabbit derived VL single-domains as promising scaffolds to generate antibody-drug conjugates

Antibody-drug conjugates (ADCs) are among the fastest-growing classes of therapeutics in oncology. Although ADCs are in the spotlight, they still present significant engineering challenges. Therefore, there is an urgent need to develop more stable and effective ADCs. Most rabbit light chains have an extra disulfide bridge, that links the variable and constant domains, between Cys80 and Cys171, which is not found in the human or mouse. Thus, to develop a new generation of ADCs, we explored the potential of rabbit-derived VL-single-domain antibody scaffolds (sdAbs) to selectively conjugate a payload to Cys80. Hence, a rabbit sdAb library directed towards canine non-Hodgkin lymphoma (cNHL) was subjected to in vitro and in vivo phage display. This allowed the identification of several highly specific VL-sdAbs, including C5, which specifically target cNHL cells in vitro and present promising in vivo tumor uptake. C5 was selected for SN-38 site-selective payload conjugation through its exposed free Cys80 to generate a stable and homogenous C5-DAB-SN-38. C5-DAB-SN-38 exhibited potent cytotoxicity activity against cNHL cells while inhibiting DNA-TopoI activity. Overall, our strategy validates a platform to develop a novel class of ADCs that combines the benefits of rabbit VL-sdAb scaffolds and the canine lymphoma model as a powerful framework for clinically translation of novel therapeutics for cancer.

Downregulation of MACC1 facilitates the reversal effect of verapamil on the chemoresistance to active metabolite of irinotecan in human colon cancer cells

The aim of this study is to investigate the reversal effect of verapamil (VER) on chemoresistance to irinotecan (CPT-11) in human colon cancer cells and relevant mechanisms. Cell counting kit-8 (CCK-8) test and colony-forming unit (CFU) experiment results show that VER strengthens the sensitivity of human colon cancer cell line HT29 to CPT-11 but has a small effect on SW480 cells. High-throughput transcriptome sequencing, RT-PCR, and Western blot results show that the inhibition of metastasis-associated in colon cancer-1 (MACC1) expression by VER is the key factor for reversal effect on chemoresistance to CPT-11. Transfection experiments further show that VER can reverse the resistance of human colon cancer cells to SN-38, the active metabolite of CPT-11, when MACC1 is overexpressed. The nude mouse transplantation tumor experiment provides an in vivo proof that VER can strengthen sensitivity to CPT-11 in drug-resistant human colon cancer cells, and the effect might be related to the inhibited expression of MACC1. In summary, VER might strengthen the reversal effect of VER on chemoresistance to CPT-11 in human colon cancer cells and facilitate the apoptosis of human colon cancer cells by downregulating MACC1 expression.

Intrinsically Disordered Protein Micelles as Vehicles for Convection-Enhanced Drug Delivery to Glioblastoma Multiforme

Lipid and micelle-based nanocarriers have been explored for anticancer drug delivery to improve accumulation and uptake in tumor tissue. As an experimental opportunity in this area, our lab has developed a protein-based micelle nanocarrier consisting of a hydrophilic intrinsically disordered protein (IDP) domain bound to a hydrophobic tail, termed IDP-2Yx2A. This construct can be used to encapsulate hydrophobic chemotherapeutics that would otherwise be too insoluble in water to be administered. In this study, we evaluate the in vivo efficacy of IDP-2Yx2A by delivering a highly potent but water-insoluble cancer drug, SN38, into glioblastoma multiforme (GBM) tumors via convection-enhanced delivery (CED). The protein carriers alone are shown to elicit minimal toxicity effects in mice; furthermore, they can encapsulate and deliver concentrations of SN38 that would otherwise be lethal without the carriers. CED administration of these drug-loaded micelles into mice bearing U251-MG GBM xenografts resulted in slowed tumor growth and significant increases in median survival times compared to nonencapsulated SN38 and PBS controls.

Cellular irinotecan resistance in colorectal cancer and overcoming irinotecan refractoriness through various combination trials including DNA methyltransferase inhibitors: a review

Treatment with pharmacological drugs for colorectal cancer (CRC) remains unsatisfactory. A major cause of failure in pharmacotherapy is the resistance of colon cancer cells to the drugs, creating an urgent issue. In this review, we summarize previous studies on the resistance of CRC cells to irinotecan and discuss possible reasons for refractoriness. Our review presents the following five major causes of irinotecan resistance in human CRC: (1) cellular irinotecan resistance is induced mainly through the increased expression of the drug efflux transporter, ABCG2; (2) cellular irinotecan resistance is also induced in association with a nuclear receptor, pregnane/steroid X receptor (PXR/SXR), which is enriched in the CYP3A4 gene enhancer region in CRC cells by exposing the cells to SN-38; (3) irinotecan-resistant cells possess either reduced DNA topoisomerase I (Top1) expression at both the mRNA and protein levels or Top1 missense mutations; (4) alterations in the tumor microenvironment lead to drug resistance through intercellular vesicle-mediated transmission of miRNAs; and (5) CRC stem cells are the most difficult targets to successfully treat CRC. In the clinical setting, CRC gradually develops resistance to initially effective irinotecan-based therapy. To solve this problem, several clinical trials, such as irinotecan plus cetuximab vs. cetuximab monotherapy, have been conducted. Another clinical trial on irinotecan plus guadecitabine, a DNA-methyltransferase inhibitor, has also been conducted.

Challenges and Opportunities to Develop Enediyne Natural Products as Payloads for Antibody-Drug Conjugates

Calicheamicin, the payload of the antibody-drug-conjugates (ADCs) gemtuzumab ozogamicin (Mylotarg^®) and inotuzumab ozogamicin (Besponsa^®), belongs to the class of enediyne natural products. Since the isolation and structural determination of the neocarzinostatin chromophore in 1985, the enediynes have attracted considerable attention for their value as DNA damaging agents in cancer chemotherapy. Due to their non-discriminatory cytotoxicity towards both cancer and healthy cells, the clinical utilization of enediyne natural products relies on conjugation to an appropriate delivery system, such as an antibody. Here we review the current landscape of enediynes as payloads of first-generation and next-generation ADCs.

Predictive biomarkers for sacituzumab govitecan efficacy in Trop-2-expressing triple-negative breast cancer

Sacituzumab govitecan (SG) is an antibody-drug conjugate composed of a humanized anti-Trop-2 IgG antibody conjugated via a hydrolysable linker to SN-38, the topoisomerase I-inhibitory active component of irinotecan. We investigated whether Trop-2-expression and homologous recombination repair (HRR) of SN-38-mediated double-strand DNA (dsDNA) breaks play a role in the sensitivity of triple-negative breast cancer (TNBC) to SG. Activation of HRR pathways, as evidenced by Rad51 expression, was assessed in SG-sensitive cell lines with low and moderate Trop-2-expression (SK-MES-1 squamous cell lung carcinoma and HCC1806 TNBC, respectively), compared to a low Trop-2-expressing, less SG-sensitive TNBC cell line (MDA-MB-231). Further, two Trop-2-transfectants of MDA-MB-231, C13 and C39 (4- and 25-fold higher Trop-2, respectively), were treated in mice with SG to determine whether increasing Trop-2 expression improves SG efficacy. SG mediated >2-fold increase in Rad51 in MDA-MB-231 but had no effect in SK-MES-1 or HCC1806, resulting in lower levels of dsDNA breaks in MDA-MB-231. SG and saline produced similar effects in parental MDA-MB-231 tumor-bearing mice (median survival time (MST) = 21d and 19.5d, respectively). However, in mice bearing higher Trop-2-expressing C13 and C39 tumors after Trop-2 transfection, SG provided a significant survival benefit, even compared to irinotecan (MST = 97d vs. 35d for C13, and 81d vs. 28d for C39, respectively; P < 0.0007). These results suggest that SG could provide better clinical benefit than irinotecan in patients with HRR-proficient tumors expressing high levels of Trop-2, as well as to patients with HRR-deficient tumors expressing low/moderate levels of Trop-2.

Irinotecan Induces Autophagy-Dependent Apoptosis and Positively Regulates ROS-Related JNK- and P38-MAPK Pathways in Gastric Cancer Cells

Background

Irinotecan (IRI) is considered an option for second-line treatment of advanced gastric cancer; however, acquired drug resistance currently limits its clinical application. Recently, many researchers have shown that autophagy plays a crucial role in the resistance of tumor cells to chemotherapy and radiotherapy. In this study, we investigated the relationship between autophagy and antitumor activity of IRI in gastric cancer cells.

Methods

We used MTT assay, flow cytometry and immunofluorescence staining to detect viability, apoptosis and autophagy in gastric cancer. Western blotting assay was used to determine the expression of LC3, Beclin-1, P62, cleaved PARP and Caspase 3. In vivo animal study was performed finally.

Results

We found that IRI treatment dose- and time-dependently inhibited growth and induced apoptosis in gastric cancer cells. Moreover, IRI treatment caused autophagy in these cells, whereas autophagy inhibitors—3-methyladenine (3-MA), chloroquine (CQ), and Beclin-1 small interfering RNA (siRNA)—suppressed cytotoxicity of IRI. A mechanistic analysis showed that IRI-induced autophagy and apoptosis were related to increased reactive oxygen species (ROS) accumulation and activation of the JNK- and p38-MAPK pathways. Further in vivo experiments revealed that IRI suppressed tumor growth, induced autophagy, and stimulated the JNK- and p38-MAPK pathways, whereas 3-MA attenuated these effects.

Conclusion

Taken together, these results indicate that IRI stimulates the ROS-related JNK- and p38-MAPK pathways to promote autophagy-dependent apoptosis. Thus, a combination of IRI with a pharmacological autophagy enhancer may be a promising therapeutic strategy against gastric cancer.

Personalized Drug Efficacy Monitoring Chip

Cancer drug resistance mechanisms such as tumor heterogeneity and adaptable feedback loops are prevalent issues facing cancer therapy development. Drug resistance can be unique to a cancer type and, most importantly, to each individual cancer patient. Consequently, testing different dosages and therapeutics directly on each individual patient sample (i.e., tumor and cancer cells) has compelling advantages compared to large scale in vitro drug testing and is a step toward personalized drug selection and effective treatment development. Recently, microfluidic-based chemo-sensitivity assays on patient biopsies have been proposed. Despite their novelty, these platforms usually rely on optical labels, optical equipment, or complex microfabricated channel geometries and structures. In this work, we proposed a novel lab on a chip platform capable of real-time and continuous screening of drug efficacy on (cancer) cell subpopulations without the need of labels or bulky readout optical equipment. In this platform, several label-free and rapid techniques have been implemented for the precise capturing of cells of interest in parallel with the real-time measurement and characterization of the effectiveness of candidate therapeutic agents. To demonstrate the utility of the platform, the effect of an apoptotic inducer, topoisomerase I inhibitor, 7-ethyl-10-hydrocamptothecin (SN38) on human colorectal carcinoma cancer cells (HCT 116) was used as a study model. Additionally, electrical results were optically verified to examine the continuous measurements of the biological mechanisms, specifically, apoptosis and necrosis, during therapeutic agent characterizations. The proposed device is a versatile platform which can also be easily redesigned for the automated and arrayed analysis of cell-drug interaction down to the single cell level. Our platform is another step toward enabling the personalized screening of drug efficacy on individual patients' samples that potentially leads to a better understanding of drug resistance and the optimization of patients' treatments.

Development of an enzyme‑linked immunosorbent assay for camptothecin

The use of camptothecin and its analogues has increased in clinical settings and in agriculture. Therefore, camptothecins and their derivatives, metabolites and degradation products are frequently found in the environment. Therefore, it is important to develop an ELISA for the quantification of camptothecins in human plasma, plants, animal tissues and other matrices. The present study developed a novel competitive indirect ELISA for camptothecin using a monoclonal antibody (MAb). In total, two haptens and various carrier proteins were tested to select the most suitable immunogen for the production of MAbs against camptothecin. Hapten 1 conjugated with keyhole limpet hemocyanin was selected for the preparation of MAb 5A3, and was used to establish a competitive indirect ELISA for camptothecin. A total of three derivatives of camptothecin used in clinical practice were examined. Topotecan showed an IC₅₀ value of 0.68 µg/ml with a detection limit of 0.19 µg/ml, belotecan showed an IC₅₀ value of 0.87 µg/ml with a detection limit of 0.22 µg/ml and irinotecan showed an IC₅₀ value of 2.85 µg/ml with a detection limit of 0.47 µg/ml. The cross-reactivity results suggested that the assay developed in the present study possessed a high sensitivity to camptothecin. Therefore, this immunoassay technique may be suitable for monitoring the levels of camptothecin in compound analysis, clinical applications, and analyses of food and environmental samples.

Camptothecin (CPT) and its derivatives are known to target topoisomerase I (Top1) as their mechanism of action: did we miss something in CPT analogue molecular targets for treating human disease such as cancer?

Camptothecin (CPT) was discovered from plant extracts more than 60 years ago. Since then, only two CPT analogues (irinotecan and topotecan) have been approved for cancer treatment, although several thousand CPT derivatives have been synthesized and many of them were actively studied in our research community over the past 6+ decades. In this review article, we briefly summarize: (1) the discovery and early development of CPTs, (2) the recognized CPT mechanism of action (MOA), (3) the synthesis of CPT and CPT analogues, and (4) the structure-activity relationship (SAR) of CPT and its analogues. Next, we provide evidence that certain CPT analogues can exert improved efficacy with low toxicity independently of topoisomerase I (Top1) inhibition; instead, these CPT analogues use novel MOAs by targeting important cancer survival-associated oncogenic proteins and/or by bypassing various treatment-resistant mechanisms. We then present a comprehensive review of the most advanced CPT analogues in clinical development, with the goal of resolving why no new CPTs have been FDA approved for cancer treatment, beyond irinotecan and topotecan. We argue that new CPT Top1 inhibitor drugs are unlikely being found to be significantly better than irinotecan and/or topotecan in terms of the overall antitumor activity and toxicity. The significance of CPT analogues that possess novel MOAs has not been sufficiently recognized so far. In our opinion, this is a research area with great potential to make a breakthrough for development of the next generation of CPT analogues that possess high efficacy (due to novel targets) and low toxicity (due to low inhibition of Top1 activity/function) for effective treatment of human disease, including cancer.

Assessing chemotherapeutic effectiveness using a paper-based tumor model

In vitro models for screening new cancer chemotherapeutics often rely on two-dimensional cultures to predict therapeutic potential. Unfortunately, the predictive power of these models is limited, as they fail to recapitulate the complex three-dimensional environments in tumors that promote a chemoresistant phenotype. In this study, we describe the preparation and characterization of paper-based cultures (PBCs) engineered to assess chemotherapeutic effectiveness in three dimensional, diffusion-limited environments. Similar environments are found in poorly vascularized tumors. Monotonic gradients develop across these cultures, which are assembled by stacking cell-laden paper scaffolds to yield thick tissue-like structures, and provide distinct chemical environments for each scaffold. After prolonged incubation, the scaffolds can simply be peeled apart and analyzed. Through fluorescence imaging, we determined that viable and proliferative cell populations were most abundant in scaffolds close to the nutrient-rich medium. By adjusting the cell density, we modulated the spatiotemporal evolution of oxygen gradients across the cultures and correlated these environmental changes with cellular sensitivity to SN-38 exposure. From these results, we showed that differences in the oxygen gradients produced cellular populations with significantly different chemosensitivities. Through this work, we highlight PBCs ability to serve as an analytical model capable of determining chemotherapeutic effectiveness under a range of chemical environments.

Chromatin determinants impart camptothecin sensitivity

Camptothecin-induced locking of topoisomerase 1 on DNA generates a physical barrier to replication fork progression and creates topological stress. By allowing replisome rotation, absence of the Tof1/Csm3 complex promotes the conversion of impending topological stress to DNA catenation and causes camptothecin hypersensitivity. Through synthetic viability screening, we discovered that histone H4 K16 deacetylation drives the sensitivity of yeast cells to camptothecin and that inactivation of this pathway by mutating H4 K16 or the genes SIR1-4 suppresses much of the hypersensitivity of tof1∆ strains towards this agent. We show that disruption of rDNA or telomeric silencing does not mediate camptothecin resistance but that disruption of Sir1-dependent chromatin domains is sufficient to suppress camptothecin sensitivity in wild-type and tof1∆ cells. We suggest that topoisomerase 1 inhibition in proximity of these domains causes topological stress that leads to DNA hypercatenation, especially in the absence of the Tof1/Csm3 complex. Finally, we provide evidence of the evolutionarily conservation of this mechanism.

Advantages of an optical nanosensor system for the mechanistic analysis of a novel topoisomerase I targeting drug: a case study

The continuous need for the development of new small molecule anti-cancer drugs calls for easily accessible sensor systems for measuring the effect of vast numbers of new drugs on their potential cellular targets. Here we demonstrate the use of an optical DNA biosensor to unravel the inhibitory mechanism of a member of a new family of small molecule human topoisomerase I inhibitors, the so-called indeno-1,5-naphthyridines. By analysing human topoisomerase I catalysis on the biosensor in the absence or presence of added drug complemented with a few traditional assays, we demonstrate that the investigated member of the indeno-1,5-naphthyridine family inhibited human topoisomerase I activity by blocking enzyme-DNA dissociation. To our knowledge, this represents the first characterized example of a small molecule drug that inhibits a post-ligation step of catalysis. The elucidation of a completely new and rather surprising drug mechanism-of-action using an optical real time sensor highlights the value of this assay system in the search for new topoisomerase I targeting small molecule drugs.

Validation and development of MTH1 inhibitors for treatment of cancer

BACKGROUND

Previously, we showed cancer cells rely on the MTH1 protein to prevent incorporation of otherwise deadly oxidised nucleotides into DNA and we developed MTH1 inhibitors which selectively kill cancer cells. Recently, several new and potent inhibitors of MTH1 were demonstrated to be non-toxic to cancer cells, challenging the utility of MTH1 inhibition as a target for cancer treatment.

MATERIAL AND METHODS

Human cancer cell lines were exposed in vitro to MTH1 inhibitors or depleted of MTH1 by siRNA or shRNA. 8-oxodG was measured by immunostaining and modified comet assay. Thermal Proteome profiling, proteomics, cellular thermal shift assays, kinase and CEREP panel were used for target engagement, mode of action and selectivity investigations of MTH1 inhibitors. Effect of MTH1 inhibition on tumour growth was explored in BRAF V600E-mutated malignant melanoma patient derived xenograft and human colon cancer SW480 and HCT116 xenograft models.

RESULTS

Here, we demonstrate that recently described MTH1 inhibitors, which fail to kill cancer cells, also fail to introduce the toxic oxidized nucleotides into DNA. We also describe a new MTH1 inhibitor TH1579, (Karonudib), an analogue of TH588, which is a potent, selective MTH1 inhibitor with good oral availability and demonstrates excellent pharmacokinetic and anti-cancer properties in vivo.

CONCLUSION

We demonstrate that in order to kill cancer cells MTH1 inhibitors must also introduce oxidized nucleotides into DNA. Furthermore, we describe TH1579 as a best-in-class MTH1 inhibitor, which we expect to be useful in order to further validate the MTH1 inhibitor concept.

Drug Resistance in Colorectal Cancer Cell Lines is Partially Associated with Aneuploidy Status in Light of Profiling Gene Expression

A priority in solving the problem of drug resistance is to understand the molecular mechanism of how a drug induces the resistance response within cells. Because many cancer cells exhibit chromosome aneuploidy, we explored whether changes of aneuploidy status result in drug resistance. Two typical colorectal cancer cells, HCT116 and LoVo, were cultured with the chemotherapeutic drugs irinotecan (SN38) or oxaliplatin (QxPt), and the non- and drug-resistant cell lines were selected. Whole exome sequencing (WES) was employed to evaluate the aneuploidy status of these cells, and RNAseq and LC-MS/MS were implemented to examine gene expression at both mRNA and protein level. The data of gene expression was well-matched with the genomic conclusion that HCT116 was a near diploid cell, whereas LoVo was an aneuploid cell with the increased abundance of mRNA and protein for these genes located at chromosomes 5, 7, 12, and 15. By comparing the genomic, transcriptomic, and proteomic data, the LoVo cells with SN38 tolerance showed an increased genome copy in chromosome 14, and the expression levels of the genes on this chromosome were also significantly increased. Thus, we first observed that SN38 could impact the aneuploidy status in cancer cells, which was partially associated with the acquired drug resistance.

Combining ABCG2 Inhibitors with IMMU-132, an Anti-Trop-2 Antibody Conjugate of SN-38, Overcomes Resistance to SN-38 in Breast and Gastric Cancers

Sacituzumab govitecan (IMMU-132), an SN-38-conjugated antibody-drug conjugate, is showing promising therapeutic results in a phase I/II trial of patients with advanced Trop-2-expressing, metastatic, solid cancers. As members of the ATP-binding cassette (ABC) transporters confer chemotherapy resistance by active drug efflux, which is a frequent cause of treatment failure, we explored the use of known inhibitors of ABC transporters for improving the therapeutic efficacy of IMMU-132 by overcoming SN-38 resistance. Two human tumor cell lines made resistant to SN-38, MDA-MB-231-S120 (human breast cancer) and NCI-N87-S120 (human gastric cancer), were established by continuous exposure of the parental cells to stepwise increased concentrations of SN-38 and analyzed by flow cytometry for functional activities of ABCG2 and ABCB1, immunoblotting and qRT-PCR for the expression of ABCG2 at both protein and mRNA levels, and MTS assays for the potency of SN-38 alone or in combination with a modulator of ABC transporters. MDA-MB-231-S120 and NCI-N87-S120 displayed reduced sensitivity to SN-38 in vitro, with IC50 values approximately 50-fold higher than parental MDA-MB-231 and NCI-N87 cells. The increase in drug resistance of both S120 cell populations is associated with the expression of functional ABCG2, but not ABCB1. Importantly, treatment of both S120 sublines with known ABCG2 inhibitors (fumitremorgin C, Ko143, and YHO-13351) restored toxicity of SN-38, and the combination of YHO-13351 with IMMU-132 increased the median survival of mice bearing NCI-N87-S120 xenografts. These results provide a rationale for combination therapy of IMMU-132 and inhibitors of ABC transporters, such as YHO-13351. Mol Cancer Ther; 15(8); 1910-9. ©2016 AACR.

Effect of mFOLFOX6 chemotherapy combined with autologous CIK cells on T lymphocyte subsets in patients with advanced colorectal cancer

AIM: To observe the effect of mFOLFOX6 chemotherapy combined with autologous cytokine-induced killer (CIK) cells on T lymphocyte subsets in patients with advanced colorectal cancer.

METHODS: Eighty-nine patients with advanced colorectal cancer treated at our hospital from January 2009 to December 2014 were selected and divided into a combination group (29 cases), a chemotherapy group (30 cases) and a CIK group (30 cases) by the random comprehensive equilibrium sequential method. The chemotherapy group was given mFOLFOX6 chemotherapy alone, the CIK group was given autologous CIK cell treatment alone, and the combination group was given mFOLFOX6 chemotherapy combined with autologous CIK cell treatment. The short-term effects, changes of T lymphocyte subsets (CD3, CD4, CD8, CD4/CD8 ratio) and adverse reactions of the three groups were observed.

RESULTS: There was a significant difference in short-term effects among the three groups (P < 0.05), and the clinical improvement rate was significantly higher in the combination group than in the chemotherapy group and CIK group (86.2% vs 53.3%, 56.67%, P < 0.05), while there was no significant difference between the chemotherapy group and CIK group (P > 0.05). There were no significant differences in CD3, CD4, CD8, or CD4/CD8 ratio among the three groups before treatment (P > 0.05). After treatment, CD3, CD4, CD8, and CD4/CD8 ratio showed no significant changes in the combination group (P > 0.05), while CD3, CD4, and CD4/CD8 in the chemotherapy group and CIK group were significantly decreased (P < 0.05), and CD8 significantly increased (P < 0.05). CD3, CD4, CD8, and CD4/CD8 ratio were significantly better in the combination group than in the chemotherapy group and CIK group (P > 0.05). The rate of adverse reactions was significantly lower in the combination group and CIK group than in the chemotherapy group (17.2%, 10.0% vs 46.7%, P < 0.05).

CONCLUSION: The short-term effects of mFOLFOX6 chemotherapy combined with autologous CIK cells for patients with advanced colorectal cancer are remarkable, and the CIK cell therapy can avoid the functional disorder of T lymphocyte subsets induced by chemotherapy and is associated with fewer adverse reactions.