p16INK4 expression is associated with the increased sensitivity of human non-small cell lung cancer cells to DNA topoisomerase I inhibitors

Analysis of topoisomerase I expression and identification of predictive markers for efficacy of topotecan chemotherapy in small cell lung cancer

Background

We evaluated topoisomerase I (TOPO1) expression in patients with small cell lung cancer (SCLC) and identified predictive factors for the efficacy of second‐line topotecan chemotherapy.

Methods

We retrospectively evaluated the records of SCLC patients treated in our department from January 2007 to December 2016 who received second‐line topotecan chemotherapy. Patients with archived tumor samples were enrolled. TOPO1 expression levels were evaluated by immunohistochemistry, and the relationships between TOPO1 expression, clinical factors, chemotherapy efficacy, and survival were analyzed.

Results

Of the 78 patients enrolled, 67 showed TOPO1 expression (85.9%). Patients were divided into strong (n = 43) or weak (n = 35) expression groups based on staining intensity. Disease control rates for topotecan were 39.5% and 14.3% in the strong and weak groups, respectively (P = 0.014). Second‐line median progression‐free survival was 2.2 and 2.0 months (P = 0.057), and median overall survival was 8.1 and 6.0 months (P = 0.199) in the strong and weak positive groups, respectively. Patients were also divided into sensitive (n = 47) and refractory (n = 31) disease groups according to the duration from the onset of first‐line therapy to relapse. Median second‐line progression‐free survival was 2.2 and 1.8 months in the sensitive and refractory relapse groups, respectively (P = 0.005).

Conclusions

TOPO1 expression was prevalent in SCLC patients. Strong expression was associated with an elevated disease control rate after second‐line topotecan chemotherapy. Patients with sensitive disease that relapsed after first‐line chemotherapy had better survival than refractory patients who received second‐line topotecan chemotherapy.

Synergism of cyclin-dependent kinase inhibitors with camptothecin derivatives in small cell lung cancer cell lines

Advanced small cell lung cancer (SCLC) has a dismal prognosis. Modulation of the camptothecin topotecan, approved for second-line therapy, may improve response. Our recent finding of synergistic enhancement of the cytotoxic activity of camptothecin (CPT) by cyclin-dependent kinase 4 inhibitors is extended here to a panel of camptothecin analogs comprising 10-hydroxy-CPT (HOCPT), topotecan (TPT; 9-[(dimethylamino)-methyl]-10-hydroxy-CPT), 9-amino-CPT (9AC), 9-nitrocamptothecin (rubitecan), SN38 (7-ethyl-10-hydroxycamptothecin) and 10-hydroxy-9-nitrocamptothecin (CPT109) in combination with PD0332991, CDK4I, roscovitine and olomoucine. SCLC cell lines employed are chemoresistant NCI-H417 and DMS153 and the chemosensitive SCLC26A line established at our institution. The CPT analogs exhibiting highest cytotoxicity towards the three SCLC lines tested were SN38 and 9AC, followed by rubitecan, HOCPT, TPT and CPT109. NCI-H417 and DMS153 revealed an approximately 25-fold and 7-fold higher resistance compared to the chemosensitive SCLC26A cell line. Whereas the CDK4/6 inhibitor PD0332991 proved less effective to chemosensitize SCLC cells to CPT analogs, the CDK inhibitors CDK4I, roscovitine and olomoucine gave comparable chemosensitization effects in combination with 9AC, SN38, rubitecan and to a lesser extent with TPT and CPT109, not directly related with topoisomerase mRNA expression. In conclusion, small chemical modifications of the parent CPT structure result in differing cytotoxicities and chemomodulatory effects in combination with CDKIs of the resulting analogs.

Relations between strain and gender dependencies of irinotecan toxicity and UGT1A1, CES2 and TOP1 expressions in mice

Irinotecan hydrochloride (CPT-11) can display severe toxicities in individual cancer patients. CPT-11 is bio-activated through CES, detoxified through UGT1A1 and inhibits TOP1. CPT-11 toxicity and UGT1A1, CES2 and TOP1 mRNAs and UGT1A1 protein were determined in male and female C57BL/6, B6D2F1 and B6CBAF1, as potential models for tailoring CPT-11 delivery. CPT-11 was administered intravenously (40-90 mg/kg/day for 4 days at 7h after light onset). The relations between dose and lethal toxicity or body weight loss were steep and similar in C57BL/6 (lethality, p=0.001; weight loss, p=0.002) and B6D2F1 (p=0.01; p=0.03, respectively), but weak in B6CBAF1. Females displayed less toxicity than males (p<0.001). Mean mRNA expression of UGT1A1 was highest in B6CBAF1 (p=0.039) and in females (p<0.001). Both CES2 and TOP1 varied according to strain and gender (p<0.001). The three gene expression data explained the most severe toxicity of CPT-11 in male B6D2F1, but displayed inconsistent relations with toxicity in the other groups. Mean UGT1A1 protein expression was highest in males as compared to females, and so by approximately 8-fold in C57BL/6 as compared to B6D2F1 (p<0.0001). Genetic background and gender significantly altered the molecular prediction of irinotecan toxicity by UGT1A1, CES2 and TOP1 mRNA expressions.

Epigenetic mechanisms of irinotecan sensitivity in colorectal cancer cell lines

Irinotecan is a topoisomerase-I (Top-I) inhibitor used for the treatment of colorectal cancer. DNA demethylating agents, including 5-azacytidine (5-aza), display synergistic antitumor activity with several chemotherapy drugs. 5-Aza may enhance irinotecan cytotoxicity by at least one of the following mechanisms: (a) Top-I promoter demethylation, (b) activation of genes involved in Top-I transcriptional regulation (p16 or Sp1), and (c) modulation of the cell cycle and apoptosis after DNA damage. The growth-inhibitory effects of SN38, the active metabolite of irinotecan, 5-aza, and their combinations, were studied in four colorectal cancer cell lines. The effects of treatments on cell cycle were analyzed by flow cytometry, and apoptosis was measured by fluorescence microscopy. Top-I, Sp1, and p53 expression modulated by 5-aza were measured by real-time PCR. Methylation of Top-I, p16, 14-3-3sigma, and hMLH1 promoters before and after 5-aza treatment were measured by MethyLight PCR and DNA bisulfite sequencing. Low-dose 5-aza significantly enhanced the apoptotic effect of irinotecan in all colorectal cancer cells, whereas a synergistic cytotoxic effect was observed only in p53-mutated cells (HT29, SW620, and WiDr). This synergistic effect was significantly correlated with Top-I up-regulation by 5-aza, and coupled to p16 demethylation and Sp1 up-regulation. p16 demethylation was also associated with enhanced cell cycle arrest after irinotecan treatment. In contrast, 5-aza down-regulated Top-I expression in the p53 wild-type LS174T cells in a p53-dependent manner, thereby reducing SN38 cytotoxicity. In conclusion, 5-aza modulates Top-I expression by several mechanisms involving Sp1, p16, and p53. If confirmed in other models, these results suggest that p16 and p53 status affects the 5-aza-irinotecan interaction.

A new cancer diagnostic system based on a CDK profiling technology

A series of molecular pathological investigations of the molecules that stimulate the cyclin dependent kinases (CDK1, 2, 4, and 6) have led to enormous accumulation of knowledge of the clinical significance of these molecules for cancer diagnosis. However, the molecules have yet to be applied to clinical cancer diagnosis, as there is no available technology for application of the knowledge in a clinical setting. We hypothesized that the direct measurement of CDK activities and expressions (CDK profiling) might produce clinically relevant values for the diagnosis. This study investigated the clinical relevance of CDK profiling in gastrointestinal carcinoma tissues by using originally developed expression and activity analysis methods. We have established novel methods and an apparatus for analyzing the expression and activities of the CDK molecules in lysate of tumor tissue in a clinical setting, and examined 30 surgically dissected gastrointestinal carcinomas and corresponding normal mucosal specimens. We demonstrate here that remarkably elevated CDK2 activity is evident in more than 70% of carcinoma tissues. Moreover, a G1-CDK activity profiling accurately mirrored the differences in proliferation between tumor and normal colonic tissues. Our results suggest that CDK profiling is a potent molecular-clinical approach to complement the conventional pathological diagnosis, and to further assist in the individualized medications.

Immunohistochemical analysis of thymidylate synthase, p16(INK4a), cyclin-dependent kinase 4 and cyclin D1 in colorectal cancers receiving preoperative chemotherapy: significance of p16(INK4a)-mediated cellular arrest as an indicator of chemosensitivity to 5-fluorouracil

High expression of thymidylate synthase (TS) is allegedly associated with the chemoresistance to 5-fluorouracil (5-FU) in colorectal cancers. However, low TS expression does not necessarily imply chemosensitivity. Inactivation of p16(INK4a) correlates with poor prognosis in various cancers. We immunohistochemically evaluated the relationship between the expression of TS, p16(INK4a), CDK4 and cyclin D1 and the effect of 5-FU-based chemotherapy in colorectal cancers. After antigen retrieval, immunoperoxidase staining was performed on the paraffin-embedded, biopsy and surgical specimens of 37 advanced colorectal cancers preoperatively treated with peroral administration of 5-FU derivatives. As a control group, 31 colorectal cancers without preoperative treatment were analyzed. High TS expression was found in 23 (74%) of 31 tumors resected from histological non-responders and in 19 (61%) of 31 controls but in none of six responders. High p16(INK4a) expression was seen in 83% of the responders, 52% of the non-responders and 32% of the controls. The TS-low/p16(INK4a)-high phenotype was noted in 83% of the responders, but only in 3% of the non-responders (P = 0.0001). Induction of p16(INK4a) expression after chemotherapy was predominantly seen in the responders. Neither CDK4 nor cyclin D1 expression was related to the chemotherapeutic effects. In conclusion, the combination of low expression of TS and induction of p16(INK4a) after chemotherapy can be important indicators of the sensitivity to 5-FU-based chemotherapy in colorectal cancers.

5-aza-2'-deoxycytidine activates the p53/p21Waf1/Cip1 pathway to inhibit cell proliferation

In addition to its demethylating function, 5-aza-2'-deoxycytidine (5-aza-CdR) also plays an important role in inducing cell cycle arrest, differentiation, and cell death. However, the mechanism by which 5-aza-CdR induces antineoplastic activity is not clear. In this study, we found that 5-aza-CdR at limited concentrations (0.01-5 microm) induces inhibition of cell proliferation as well as increased p53/p21(Waf1/Cip1) expression in A549 cells (wild-type p53) but not in H1299 (p53-null) and H719 cells (p53 mutant). The p53-dependent p21(Waf1/Cip1) expression induced by 5-aza-CdR was not seen in A549 cells transfected with the wild-type human papilloma virus type-16 E6 gene that induces p53 degradation. Furthermore, deletion analysis and site-directed mutagenesis of the p21 promoter reveals that 5-aza-CdR induces p21(Waf1/Cip1) expression through two p53 binding sites in the p21 promoter. Finally, 5-aza-CdR-induced p21(Waf1/Cip1) expression was dependent on DNA damage but not on DNA demethylation as demonstrated by comet assay and bisulfite sequencing, respectively. Our data provide useful clues for judging the therapeutic efficacy of 5-aza-CdR in the treatment of human cancer cells.

Pharmacogenetics of anticancer drug sensitivity in non-small cell lung cancer

In mammalian cells, the process of malignant transformation is characterized by the loss or down-regulation of tumor-suppressor genes and/or the mutation or overexpression of proto-oncogenes, whose products promote dysregulated proliferation of cells and extend their life span. Deregulation in intracellular transduction pathways generates mitogenic signals that promote abnormal cell growth and the acquisition of an undifferentiated phenotype. Genetic abnormalities in cancer have been widely studied to identify those factors predictive of tumor progression, survival, and response to chemotherapeutic agents. Pharmacogenetics has been founded as a science to examine the genetic basis of interindividual variation in drug metabolism, drug targets, and transporters, which result in differences in the efficacy and safety of many therapeutic agents. The traditional pharmacogenetic approach relies on studying sequence variations in candidate genes suspected of affecting drug response. However, these studies have yielded contradictory results because of the small number of molecular determinants of drug response examined, and in several cases this approach was revealed to be reductionistic. This limitation is now being overcome by the use of novel techniques, i.e., high-density DNA and protein arrays, which allow genome- and proteome-wide tumor profiling. Pharmacogenomics represents the natural evolution of pharmacogenetics since it addresses, on a genome-wide basis, the effect of the sum of genetic variants on drug responses of individuals. Development of pharmacogenomics as a new field has accelerated the progress in drug discovery by the identification of novel therapeutic targets by expression profiling at the genomic or proteomic levels. In addition to this, pharmacogenetics and pharmacogenomics provide an important opportunity to select patients who may benefit from the administration of specific agents that best match the genetic profile of the disease, thus allowing maximum activity.

SN-38 induces cell cycle arrest and apoptosis in human testicular cancer

OBJECTIVE

CPT-11 is one of the most widely used camptothecin analogues and is converted to form the active metabolite SN-38. Clinical trials are ongoing to better characterize its spectra of clinical activity, to determine the optimal schedules of administration, and to define the usage in combination with other chemotherapeutic compounds.

MATERIALS AND METHODS

KU-MT, an AFP-producing testicular carcinoma cell line, was exposed to SN-38, etoposide, or cisplatin for 24 h, and the resulting cytotoxicity was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazonium bromide (MTT) assay. This paper describes the effects of SN-38 on the cell proliferation and cell cycle of testicular tumor cells in culture.

RESULTS

SN-38 was shown to inhibit KU-MT cell growth more potently than either etoposide or cisplatin. A marked decrease in the percentage of S phase cells was accompanied by the enhancement of cyclin E levels. In concentrations of >30 nmol/l, SN-38 arrested the cell cycle in G2 and induced cell death via apoptosis. The apoptosis was promoted by Bax and p53 protein, which were both shown to be present by flow cytometric and Western blot analyses.

CONCLUSION

These results suggest that CPT-11, a pro-drug of SN-38, may be clinically useful for the treatment of testicular cancer, and that the mechanism of this agent's cytotoxicity consists of cell cycle arrest and concomitant apoptosis.

Inactivation of p16/CDKN2 and p15/MTS2 is associated with prognosis and response to chemotherapy in ovarian cancer

To define the involvement of p16/CDKN2 and p15/MTS2 tumor-suppressor genes for response to chemotherapy in primary epithelial ovarian cancer, we analyzed alterations of the gene in 45 patients who were treated with primary cytoreductive surgery followed by 6 courses of cis-diamminedichloroplatinum (II) (cisplatin)-based combination chemotherapy. Homozygous deletion of p16/CDKN2 and p15/MTS2 genes was found in 8 (18%) and 15 (33%) cases, respectively. Response to the chemotherapy was confirmed by finding at second surgery after the chemotherapy in 26 patients, resulting in 17 responders and 9 nonresponders. The abundance of gene deletion in nonresponders (56%) was significantly higher (p = 0.0463) when compared to that in responders (18%). Moreover, the deletion of genes was a significant poor prognostic factor (p = 0.0441) in advanced ovarian cancer. These results suggest that deletion of p16/CDKN2 and/or p15/MTS2 is a potential indicator for poor chemotherapy response and adverse prognosis in ovarian cancer patients.

Pharmacogenetic determinants of anti-cancer drug activity and toxicity

Cellular responses to anti-cancer agents result from the interaction between drugs, cellular targets and mechanisms of damage repair. Despite the pharmacological advances in the treatment of cancer, the clinical efficacy of chemotherapy is unpredictable in most patients. However, new information on the genetics of cancer delineates strategies by which the genetic background of tumour cells and patients might be profiled to select anti-cancer agents with improved efficacy and tolerability. This article focuses on the application of pharmacogenetics in the characterization of differences in the pharmacokinetics and pharmacodynamics of anti-cancer agents among individuals to define the likelihood of response and reduce the incidence of adverse effects.

Gene therapy for pancreatic cancer--current and prospective strategies

Pancreatic ductal adenocarcinoma is one of the most common causes of cancer death in the developed world. Long-term survival is currently only achieved through surgical resection. Most patients have locally advanced or metastatic disease at the time of diagnosis and are therefore not amenable to resection, whilst chemotherapy and radiotherapy are by and large ineffective. Gene therapy offers an alternative to current adjuvant strategies. With approximately two-thirds of all gene therapy trials worldwide directed at cancer, the gene therapy approaches that are currently being explored for pancreatic cancer are specifically examined. Gene delivery systems, genetic targets, and combined gene delivery with chemotherapy are discussed in the context of pancreatic cancer treatment.

Ectopic p16(ink4) expression enhances CPT-11-induced apoptosis through increased delay in S-phase progression in human non-small-cell-lung-cancer cells

A tumor-suppressor gene, p16(INK4), which is deleted or mutated in tumors, regulates cell-cycle progression through a G(1)-S restriction point by inhibiting CDK4(CDK6)/cyclin-D-mediated phosphorylation of pRb. We have found that ectopic p16(INK4) expression increased cellular sensitivity of human non-small-cell-lung-cancer (NSCLC) A549 cells to a selective growth-inhibitory effect induced by the topoisomerase-I inhibitor 11, 7-ethyl-10-[4-(1-piperidino)-1-piperidino] carbonyloxy camptothecin (CPT-11) in vitro. In this study, we observed enhanced apoptosis characterized by DNA fragmentation in A549 cells transfected with p16(INK4) cDNA (A549/p16-1) and treated with CPT-11. This apoptosis was suppressed by the inhibitor of interleukin-1beta-converting enzyme (ICE/caspase-1) or ICE-like proteases, Z-Asp-CH2-DCB, as determined by DNA fragmentation and proteolytic cleavage of poly(ADP-ribose) polymerase, a natural substrate for CPP32/caspase-3. In A549/p16-1 cells, cytosolic peptidase activities that cleaved Z-DEVD-7-amino-4-trifluoromethylcoumarin increased during CPT-11-induced apoptosis and were suppressed by a highly specific caspase-3 and caspase-3-like inhibitor, Z-DEVD-fluoromethylketone. These findings indicate that p16(INK) is positively involved in the activation pathway of the caspase-3 induced by CPT-11. The increased delay in S-phase progression and subsequent induction of apoptosis were observed in CPT-11-treated A549/p16-1 cells on the basis of DNA histograms. Specific down-regulation of the cyclin-A protein level in A549/p16-1 cells was observed after CPT-11-treatment, whereas cyclin B, cdk2, and cdc2 protein levels were unaffected. These results suggest that ectopic p16(INK4) expression inappropriately decreases cyclin A and thereby terminates CPT-11-induced G(2)/M accumulation, which is followed by increased apoptosis in p16(INK4)-expressing A549 cells.

DNA methyltransferase inhibition induces the transcription of the tumor suppressor p21(WAF1/CIP1/sdi1)

Previous lines of evidence have shown that inhibition of DNA methyltransferase (MeTase) can arrest tumor cell growth; however, the mechanisms involved were not clear. In this manuscript we show that out of 16 known tumor suppressors and cell cycle regulators, the cyclin-dependent kinase inhibitor p21 is the only tumor suppressor induced in the human lung cancer cell line, A549, following inhibition of DNA MeTase by a novel DNA MeTase antagonist or antisense oligonucleotides. The rapid induction of p21 expression points to a mechanism that does not involve demethylation of p21 promoter. Consistent with this hypothesis, we show that part of the CpG island upstream of the endogenous p21 gene is unmethylated and that the expression of unmethylated p21 promoter luciferase reporter constructs is induced following inhibition of DNA MeTase. These results are consistent with the hypothesis that the level of DNA MeTase in a cell can control the expression of a nodal tumor suppressor by a mechanism that does not involve DNA methylation.

Drug resistance in lung cancer

The major problem in lung cancer chemotherapy is the emergence of inherent and acquired drug resistance of the cancer cells. Establishment of drug-resistant sublines and comparative investigations of such cell lines with their parental cells to determine their molecular, biologic, and biochemical properties are important research strategies. Genetic changes in tumor cells may induce changes in their biochemical properties and chemosensitivity. Many mechanisms that render tumor cells resistant have been identified, and they have provided new molecular targets for surrogate markers to predict chemosensitivity. The new categories of anticancer drugs, such as topoisomerase I inhibitors and taxanes, and non-cytotoxic new drugs, have been introduced clinically. It is important to define the molecular determinants of resistance to these drugs. The development of an appropriate model for overcoming drug resistance is one of the important issues that should be solved before carrying out further clinical trials.