Taxanes in lung cancer: a review with focus on the European experience

Chemotherapy reinforces anti-tumor immune response and enhances clinical efficacy of immune checkpoint inhibitors

New evidence suggests that the clinical success of chemotherapy is not merely due to tumor cell toxicity but also arises from the restoration of immunosurveillance, which has been immensely neglected in previous preclinical and clinical researches. There is an urgent need for novel insights into molecular mechanisms and regimens that uplift the efficacy of immunotherapy since only a minority of cancer patients are responsive to immune checkpoint inhibitors (ICIs). Recent findings on combination therapy of chemotherapy and ICIs have shown promising results. This strategy increases tumor recognition and elimination by the host immune system while reducing immunosuppression by the tumor microenvironment. Currently, several preclinical studies are investigating molecular mechanisms that give rise to the immunomodulation by chemotherapeutic agents and exploit them in combination therapy with ICIs in order to achieve a synergistic clinical activity. In this review, we summarize studies that exhibit the capacity of conventional chemotherapeutics to elicit anti-tumor immune responses, thereby facilitating anti-tumor activities of the ICIs. In conclusion, combining chemotherapeutics with ICIs appears to be a promising approach for improving cancer treatment outcomes.

Molecular basis and rationale for combining immune checkpoint inhibitors with chemotherapy in non-small cell lung cancer

Immunotherapy has prompted a paradigm shift in advanced non-small cell lung cancer (NSCLC) treatment, by demonstrating superior efficacy to chemotherapy alone both in second- and in first-line setting. Novel insights on molecular mechanisms and regimens to enhance the efficacy of immunotherapy are warranted, as only a minority of patients (˜20%) respond to checkpoint blockade. Taking into account the multiple mechanisms adopted by tumor cells to evade the immune system through cancer immunoediting, the frontline combination of immune checkpoint inhibitors with chemotherapy appears to be a successful strategy as: 1) it enhances the recognition and elimination of tumor cells by the host immune system (immunogenic cell-death), and 2) it reduces the immunosuppressive tumor microenvironment. Remarkably, the immune checkpoint inhibitors pembrolizumab and atezolizumab have already been approved by the FDA in combination with chemotherapy for the first-line treatment of advanced NSCLC and many other chemo-immunotherapeutic regimens have been evaluated as an initial therapeutic approach in metastatic NSCLC. Concurrently, several preclinical studies are evaluating the molecular mechanisms underlying immunomodulation by conventional chemotherapeutic agents (platinum salts, antimitotic agents, antimetabolites and anthracyclines), unraveling drug- and dose/schedule-dependent effects on the immune system that should be exploited to achieve synergistic clinical activity. The current review provides a detailed overview of the immunobiological rationale and molecular basis for combining immune checkpoint inhibitors with chemotherapy for the treatment of advanced NSCLC. Moreover, current evidence and future perspectives towards a better selection of patients who are more likely to benefit from chemo-immunotherapy combinations are discussed.

Novel hydrophilic docetaxel (CQMU-0519) analogue inhibits proliferation and induces apoptosis in human A549 lung, SKVO3 ovarian and MCF7 breast carcinoma cell lines

OBJECTIVE

Objectives of this investigation were not merely to perform a comparative study with original docetaxel, but to define anti-proliferative and apoptotic effects of novel hydrophilic docetaxel (CQMU-0519) analogue on A549 lung, SKVO3 ovary and MCF7 breast carcinoma cell lines.

MATERIALS AND METHODS

The materials for the study consist of a completely new docetaxel analogue (CQMU-0519), synthesized by the Department of Pharmacology, Chongqing Medical University, China, which is completely soluble in water. 50 nm of drug concentration was utilized on all three cell lines where cell population growth was assessed using cell culture kit-8 and flow cytometry analysis, whereas apoptotic pathways were unveiled by use of annexin-V FITC, apoptosis DNA ladder, caspases-3, 6, 8 and 9; in the meanwhile, regulation of Bcl-2 family members was analysed by western blotting.

RESULT

The novel docetaxel analogue (CQMU-0519) suppressed cell proliferation in all three cell lines, inhibition of cell proliferation and cell cycle arrest being more evident in G(2) /M phase. Also, in both lung and ovarian cell lines, apoptotic levels were higher as measured by the various tests performed, and downregulation of Bcl-2 and Bcl-xL with increased expressions of Bad and Bax indicated the intrinsic pathway for apoptosis. Nevertheless, it was found that MCF7 cells, although also manifesting high levels of apoptosis, used the extrinsic pathway instead. Hence, it was shown that novel docetaxel analogue (CQMU-0519) may have some prospective use in future clinical trials.

CONCLUSIONS

Novel hydrophilic docetaxel analogue (CQMU-0519) inhibited cell proliferation and enhanced the intrinsic apoptotic pathway in lung and ovarian carcinoma cells, whereas it used the extrinsic one in breast adenocarcinoma cells.

Development of taxane resistance in a panel of human lung cancer cell lines

Using a selection process designed to reflect clinically relevant conditions, a panel of taxane-selected variants were developed to study further the mechanisms of resistance in lung cancer. Unlike continuous or pulse exposure to high concentrations of chemotherapeutic drugs which yield high resistance and often cross resistance, most variants developed here displayed low level resistance to the selecting drug with slight cross-resistance. Pulsing with taxol resulted in more highly resistant clones (up to 51.4-fold). Analysis of taxol and taxotere in the four major lung cancer cell types showed the taxanes to be more effective against NSCLC (with the exception of SKMES-taxane selected variants) than against the SCLC. Comparison of taxol and taxotere shows that taxol induces higher levels of resistance than taxotere. Further, in taxotere-selected cell lines, the cells are more resistant to taxol than taxotere, suggesting that taxotere may be a superior taxane from a clinical view. Taxol treatment resulted in increased cross-resistance to 5-FU in all classes of lung cancer except DMS-53. The high levels of Pgp in the DMS-53 and selected variant suggests this mechanism is not related to Pgp expression. Analysis of the Pgp and MRP-1 status by combination inhibitory assays and Western blotting showed no consistent relationship between expression of the membrane pumps Pgp or MRP-1 and resistance. However, where high level resistance was seen, the parent cell line expressed Pgp or MRP-1 and was accompanied by increased levels in the variants. Overall we found that the clinically relevant models used here are useful for investigating mechanisms of taxane resistance.

Anti-angiogenic drugs: from bench to clinical trials

Angiogenesis, the generation of new capillaries through a process of pre-existing microvessel sprouting, is under stringent control and normally occurs only during embryonic and post-embryonic development, reproductive cycle, and wound repair. However, in many pathological conditions (solid tumor progression, metastasis, diabetic retinopathy, hemangioma, arthritis, psoriasis and atherosclerosis among others), the disease appears to be associated with persistent upregulated angiogenesis. The development of specific anti-angiogenic agents arises as an attractive therapeutic approach for the treatment of cancer and other angiogenesis-dependent diseases. The formation of new blood vessels is a complex multi-step process. Endothelial cells resting in the parent vessels are activated by an angiogenic signal and stimulated to synthesize and release degradative enzymes allowing endothelial cells to migrate, proliferate and finally differentiate to give rise to capillary tubules. Any of these steps may be a potential target for pharmacological intervention. In spite of the disappointing results obtained initially in clinical trials with anti-angiogenic drugs, recent reports with positive results in phases II and III trials encourage expectations in their therapeutic potential. This review discusses the current approaches for the discovery of new compounds that inhibit angiogenesis, with emphasis on the clinical developmental status of anti-angiogenic drugs.

Taxane‐Platinum Combinations in Advanced Non‐Small Cell Lung Cancer: A Review

Platinum-based chemotherapy is the treatment of choice for patients with non-small cell lung cancer (NSCLC). As a result of their single-agent activities and synergistic effects, taxane-platinum combinations are often used as first-line therapy for this disease. Four large, multicenter, randomized phase III clinical trials (the TAX 326 trial, the Southwest Oncology Group 9509 trial, the Italian Lung Cancer Project, and the Eastern Cooperative Oncology Group 1594 trial) have compared taxane-platinum combinations (docetaxel and paclitaxel) with other platinum combinations (vinorelbine and gemcitabine) in chemotherapy-naïve patients with good performance status scores and advanced disease. The end points for these large randomized clinical trials were survival, response rate, adverse events, and quality of life (QOL). Of the taxane-platinum combinations tested, docetaxel-cisplatin was the only platinum combination to yield survival and response rates superior to another platinum combination. In adverse event terms, the taxane-platinum combination of paclitaxel-carboplatin demonstrated less grade 3 or 4 neutropenia and lower rates of febrile neutropenia than other taxane-platinum combinations but higher rates of irreversible grade 3 or 4 peripheral neuropathy than any of the other taxane-platinum combinations. Additional differences emerged when QOL data were evaluated. The docetaxel-platinum combination demonstrated broad QOL benefits for patients receiving this combination, and this benefit was not observed with the other platinum or taxane-platinum combinations. As our use of these taxane-platinum combinations expands, these differences in survival, response rate, adverse events, and QOL will permit us to better balance our treatment goals for all patients with all stages of NSCLC.

Tubulin polymerizing activity of dictyostatin-1, a polyketide of marine sponge origin

Dictyostatin-1 had previously been isolated from a marine sponge of the genus Spongia sp. and described as a cytotoxic agent to murine and human cancer cells, but its mechanism of activity was unknown. In a routine screening assay used to detect cytotoxic compounds of marine origin, dictyostatin-1 was identified as a highly active component in an extract from a Lithistida sponge and exploration into its pharmacology was pursued. Initial studies demonstrated that dictyostatin-1 arrested cells in the G(2)/M phase of the cell cycle. Staining of these cells with antitubulin revealed cells having multiple aster formations and microtubule matrix bundling patterns similar to that seen in cells exposed to paclitaxel. Dictyostatin-1 was able to induce the polymerization of purified bovine brain tubulin in vitro and the polymerized tubulin remained stable at cold temperatures. Dictyostatin-1 also proved to be highly potent in two paclitaxel-resistant human cancer cell lines expressing active P-glycoprotein. Together, these results indicate that dictyostatin-1 is a potent inducer of tubulin polymerization and retains activity in cells expressing the P-glycoprotein efflux pump.

Comparison of antiangiogenic activities using paclitaxel (taxol) and docetaxel (taxotere)

Tumor growth requires a competent vascular supply and angiogenesis has been considered as a potential target for the treatment of several cancers. The two clinically approved taxanes, paclitaxel and docetaxel, are novel antimitotic agents that are under extensive investigation in clinical trials. Both taxanes have demonstrated significant activity against many solid tumors, but little is known about the effect of paclitaxel and docetaxel on endothelial cell function and angiogenic processes. The purpose of our study was to examine and compare the effects of these drugs on angiogenic processes in vitro and in vivo. These processes include: proliferation, migration and differentiation of cultured human umbilical vein endothelial cells (HUVEC) (in vitro), capillary sprouting of rat aortic ring explants (ex vivo) and HT1080 tumor growth in vivo. Our results demonstrate that endothelial cells are 10-100-fold more sensitive to these drugs than tumor cells. Additionally, comparison of the taxanes demonstrated that angiogenesis is blocked by both drugs primarily via inhibition of proliferation and differentiation (tube assay) and induction of cell death. Docetaxel, however, appears to be more potent at inhibiting angiogenesis, with an IC(50) concentration 10x less than that of paclitaxel. We conclude that these important findings should be taken in account in clinical trials where tumor angiogenesis is being targeted.

Weekly paclitaxel in the treatment of metastatic and/or recurrent non-small cell lung cancer

Weekly paclitaxel was initially used to exploit the radiosensitizing properties of the drug. However, the observed improvement in therapeutic index with this regimen encouraged further use of weekly regimens, with and without radiotherapy, as a single-agent or in combination with other regimens. Single-agent weekly paclitaxel, at doses ranging from 50 to 200 mg/m(2)/week, has been associated with response rates of 23-56% with acceptable toxicity. Weekly paclitaxel has also been combined with carboplatin and vinorelbine in two-drug combinations and with cisplatin plus gemcitabine and cisplatin plus vinorelbine in three-drug regimens. Response rates with weekly paclitaxel in combination chemotherapy have ranged from 16 to 71%. Paclitaxel is particularly suited to combined modality therapy with radiation in non-small cell lung cancer, because of its modest toxicity profile, significant antineoplastic activity, ease of administration and potential for radiosensitization. Studies of weekly paclitaxel given together with radiotherapy, with or without carboplatin, have produced response rates of 71-86% with median survival durations of 17-20.5 months.

Intensive chemotherapy with whole blood stem-cell support and concurrent chest radiotherapy in small cell lung cancer: a phase I/II trial

Intensive chemotherapy combined with chest radiation may ameliorate survival in small cell lung cancer (SCLC). In a prospective study, we treated 18 patients with limited SCLC with an intensive sequential single agent (ifosfamide, carboplatin, etoposide and paclitaxel, (ICE-T)) chemotherapy with the support of unprocessed stem-cell enriched whole blood and G-CSF and concomitant bi-fractionated chest radiotherapy (60 Gy). The treatment was delivered in a short time of 10 weeks. The results were compared with an historical patient group treated with six cycles of standard chemotherapy of etoposide and cisplatin and concomitant chest radiotherapy. After a 3-year median follow up, the 2-year progression free (PFS) and overall survival (OS) are 54 and 63% in the ICE-T group, respectively. In the control group, median PFS and OS were 13 and 17 months and the 2-year PFS and OS were 32% (P=0.20) and 47% (P=0.25), respectively. This short and intensive chemo-radiotherapy regimen is well tolerated and induces promising survival results. The use of stem cell enriched whole blood should be investigated in larger randomized studies.