Therapeutic efficiency of everolimus and lapatinib in xenograft model of human colorectal carcinoma with KRAS mutation

A phase II study of everolimus in patients with advanced solid malignancies with TSC1, TSC2, NF1, NF2 or STK11 mutations

Background

Activation of the mTOR pathway has been implicated in the development of several malignancies and alterations in TSC1, TSC2, STK11 and NF1, can lead to the dysregulation of this pathway. Furthermore, mutations in TSC1 and NF2 are known to confer sensitivity to everolimus-an mTOR inhibitor. Based on these data, a single-arm, open label, single-institution phase II basket study was designed to assess the activity of everolimus in patients with solid malignancies whose tumors harbored mutations in TSC1, TSC2, NF1, NF2, or STK11.

Methods

A total of 12 patients with histologically confirmed diagnosis of advanced solid tumors (metastatic, recurrent, or unresectable) with mutations in TSC1, TSC2, NF1, NF2 or STK11 genes, who had failed at least one line of standard of care systemic therapy, were enrolled to this open label, single-arm study. Presence of mutations in TSC1, TSC2, NF1, NF2 or STK11 genes was assessed using targeted-next generation sequencing (NGS). All eligible patients were treated with everolimus at an initial dose of 10 mg orally once daily in cycles of 28 days. The primary endpoint of this study was overall response rate (ORR).

Results

Of 12 patients enrolled, 8 were evaluable for response at the end of 2 cycles. One complete response (CR) was observed (12.5%) and one patient (12.5%) had stable disease (SD), while six (75%) patients showed disease progression. Everolimus was overall well tolerated with anemia, decreased neutrophil and lymphocyte counts, peripheral edema and hyperglycemia representing the most common adverse events. One patient discontinued treatment due to a treatment related grade 4 pericardial effusion. Both patients with CR or SD had a diagnosis of lung adenocarcinoma with NF1 or STK11 mutations, respectively.

Conclusions

Although this study failed to meet its prespecified ORR threshold for success of 30% or higher, exploratory analyses suggest potential activity for everolimus in a subset of patients with lung adenocarcinomas with STK11 or NF1 mutations. Further studies are necessary to systematically explore the clinical activity of everolimus, potentially as a combination therapy, in these patients.

PTRF suppresses the progression of colorectal cancers

As a key component of caveolae structure on the plasma membrane, accumulated evidence has suggested that Polymerase I and Transcript Release Factor (PTRF) plays a pivotal role in suppressing the progression of human malignances. However, the function of PTRF in the development of colorectal cancers is still unclear. Here we report that the expression of PTRF is significantly reduced in tumor tissues derived from human patients with colorectal cancers, and that the downregulation of PTRF correlates to the advanced stage of the disease. In addition, we found that the expression of PTRF negatively regulates the tumorigenic activities of colorectal cell lines (Colo320, HT29 and CaCo2). Furthermore, ectopic PTRF expression caused significant suppression of cellular proliferation, and anchorage-independent colony growth of Colo320 cells, which have the lowest expression level of PTRF in the three studied cell lines. Meanwhile, shRNA mediated knockdown of PTRF in CaCo2 cells significantly promoted cellular proliferation and anchorage-independent colony growth. In addition, in vivo assays further revealed that tumor growth was significantly inhibited in xenografts with ectopic PTRF expression as compared to untreated Colo320 cells, but was markedly enhanced in PTRF knockdown CaCo2 cells. Biochemical studies revealed that overexpression of PTRF led to the suppression of the AKT/mTOR pathway, as evidenced by reduced phosphorylation of AKT, mTOR, and downstream MMP-9. Thus, these findings, for the first time, demonstrated that PTRF inhibits the tumorigenesis of colorectal cancers and that it might serve as a potential therapeutic target for human colon cancer patients.

Synergistic antitumor activity of regorafenib and lapatinib in preclinical models of human colorectal cancer

Regorafenib significantly prolongs overall survival in patients with metastatic colorectal cancer (mCRC), but the overall clinical efficacy of regorafenib remains quite limited. Combination chemotherapy is a potentially promising approach to enhance anticancer activity, overcome drug resistance, and improve disease-free and overall survival. The current study investigates the antitumor activity of regorafenib in combination with lapatinib in preclinical models of human CRC. Our results show improved antitumor efficacy when regorafenib is combined with lapatinib both in vitro and in vivo. Furthermore, pharmacokinetic analyses revealed that regorafenib and lapatinib do not influence on each plasma concentration. The finding that regorafenib in combination with lapatinib have synergistic activity warrants further clinical investigation of this beneficial combination as a potential treatment strategy for CRC patients.

mTOR inhibitors in urinary bladder cancer

Despite the great scientific advances that have been made in cancer treatment, there is still much to do, particularly with regard to urinary bladder cancer. Some of the drugs used in urinary bladder cancer treatment have been in use for more than 30 years and show reduced effectiveness and high recurrence rates. There have been several attempts to find new and more effective drugs, to be used alone or in combination with the drugs already in use, in order to overcome this situation.The biologically important mammalian target of rapamycin (mTOR) pathway is altered in cancer and mTOR inhibitors have raised many expectations as potentially important anticancer drugs. In this article, the authors will review the mTOR pathway and present their experiences of the use of some mTOR inhibitors, sirolimus, everolimus and temsirolimus, in isolation and in conjunction with non-mTOR inhibitors cisplatin and gemcitabine, on urinary bladder tumour cell lines. The non-muscle-invasive cell line, 5637, is the only one that exhibits a small alteration in the mTOR and AKT phosphorylation after rapalogs exposure. Also, there was a small inhibition of cell proliferation. With gemcitabine plus everolimus or temsirolimus, the results were encouraging as a more effective response was noticed with both combinations, especially in the 5637 and T24 cell lines. Cisplatin associated with everolimus or temsirolimus also gave promising results, as an antiproliferative effect was observed when the drugs were associated, in particular on the 5637 and HT1376 cell lines. Everolimus or temsirolimus in conjunction with gemcitabine or cisplatin could have an important role to play in urinary bladder cancer treatment, depending on the tumour grading.

Combination of cetuximab and PP242 synergistically suppress the progression of wild-type KRAS colorectal carcinoma

Mammalian target of rapamycin (mTOR) has been shown to be overactive in human colorectal cancer, but the first-generation mTOR inhibitor, rapamycin, has failed to show clinical efficacy against colorectal cancer. On the other hand, although the second-generation mTOR inhibitor, PP242, has exerted substantial efficacy, it was revealed that independent inhibition by PP242 was transient, which could lead to positive-feedback loop to EGFR. Using wild-type KRAS colorectal cancer cells as models, we investigate the treatment efficacy of a widely used anti-EGFR monoclonal antibody, cetuximab, and PP242, alone or in combination in vitro and in vivo. Results of cell viability assays confirmed the synergistic inhibitory effect of PP242 and cetuximab on the survival of Caco-2 and HT-29 cells. Moreover, the ability of cancer-cell invasion and proliferation was also significantly inhibited by the combination therapy when compared with cetuximab or PP242 alone. Interestingly, the percentage of CD44-positive cancer cells was substantially decreased by the combination therapy in comparison with PP242 alone through fluorescence-activated cell sorting. The growth of cancer stem-like cell spheres in vitro was also maximally inhibited by combination therapy, in terms of either diameter or number. More importantly, the efficacy of combination therapy was more prominent than either drug alone in established tumor xenografts. These findings supported the potential use of combination therapy of PP242 and cetuximab against wild-type KRAS colorectal carcinomas.

A phase I open-label study of the safety, tolerability, and pharmacokinetics of pazopanib in combination with irinotecan and cetuximab for relapsed or refractory metastatic colorectal cancer

BACKGROUND

Pazopanib is a multi-targeted tyrosine kinase inhibitor shown to be clinically active in the treatment of various cancer types. This study aimed to evaluate the maximum tolerated regimen (MTR), safety, and pharmacokinetics of pazopanib in combination with irinotecan and cetuximab in adult patients with relapsed or refractory metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

This was a Phase I, 3 + 3 design, open-label, dose-escalation study (NCT0050943; VEG108925) conducted in sequential cohorts to determine the MTR of pazopanib and irinotecan administered with cetuximab. Twenty-five patients received treatment in three dosing cohorts and were evaluated for safety and tolerability of the combination and pharmacokinetics of individual drugs.

RESULTS

The MTR was determined to be 400 mg pazopanib per day orally in combination with 150 mg/m(2) irinotecan biweekly and 250 mg/m(2) cetuximab weekly by infusion. Neutropenia was the main dose-limiting toxicity. Pharmacokinetic results suggested that the overall systemic exposure to SN-38, the active metabolite of irinotecan, was affected by pazopanib to a greater extent than was the systemic exposure to irinotecan itself.

CONCLUSIONS

This study provided evidence for the manageable safety profile and feasibility of using the novel triplet combination of pazopanib, irinotecan, and cetuximab in patients with refractory mCRC. Further large-scale Phase II studies are warranted.

A phase I trial of everolimus in combination with 5-FU/LV, mFOLFOX6 and mFOLFOX6 plus panitumumab in patients with refractory solid tumors

PURPOSE

This phase I study investigated the safety, dose-limiting toxicity, and efficacy in three cohorts all treated with the mTOR inhibitor everolimus that was delivered (1) in combination with 5-fluorouracil with leucovorin (5-FU/LV), (2) with mFOLFOX6 (5-FU/LV + oxaliplatin), and (3) with mFOLFOX6 + panitumumab in patients with refractory solid tumors.

METHODS

Patients were accrued using a 3-patient cohort design consisting of two sub-trials in which the maximum tolerated combination (MTC) and dose-limiting toxicity (DLT) of everolimus and 5-FU/LV was established in Sub-trial A and of everolimus in combination with mFOLFOX6 and mFOLFOX6 plus panitumumab in Sub-trial B.

RESULTS

Thirty-six patients were evaluable for toxicity, 21 on Sub-trial A and 15 on Sub-trial B. In Sub-trial A, DLT was observed in 1/6 patients enrolled on dose level 1A and 2/3 patients in level 6A. In Sub-trial B, 2/3 patients experienced DLT on level 1B and subsequent patients were enrolled on level 1B-1 without DLT. Three of six patients in cohort 2B-1 experienced grade 3 mucositis, and further study of the combination of everolimus, mFOLFOX6 and panitumumab was aborted. Among the 24 patients enrolled with refractory metastatic colorectal cancer, the median time on treatment was 2.7 months with 45 % of patients remaining on treatment with stable disease for at least 3 months.

CONCLUSIONS

While a regimen of everolimus in addition to 5-FU/LV and mFOLFOX6 appears safe and tolerable, the further addition of panitumumab resulted in an unacceptable level of toxicity that cannot be recommended for further study. Further investigation is warranted to better elucidate the role which mTOR inhibitors play in patients with refractory solid tumors, with a specific focus on mCRC as a potential for the combination of this targeted and cytotoxic therapy in future studies.

Targeting mTOR network in colorectal cancer therapy

The mechanistic target of rapamycin (mTOR) integrates growth factor signals with cellular nutrient and energy levels and coordinates cell growth, proliferation and survival. A regulatory network with multiple feedback loops has evolved to ensure the exquisite regulation of cell growth and division. Colorectal cancer is the most intensively studied cancer because of its high incidence and mortality rate. Multiple genetic alterations are involved in colorectal carcinogenesis, including oncogenic Ras activation, phosphatidylinositol 3-kinase pathway hyperactivation, p53 mutation, and dysregulation of wnt pathway. Many oncogenic pathways activate the mTOR pathway. mTOR has emerged as an effective target for colorectal cancer therapy. In vitro and preclinical studies targeting the mTOR pathway for colorectal cancer chemotherapy have provided promising perspectives. However, the overall objective response rates in major solid tumors achieved with single-agent rapalog therapy have been modest, especially in advanced metastatic colorectal cancer. Combination regimens of mTOR inhibitor with agents such as cytotoxic chemotherapy, inhibitors of vascular endothelial growth factor, epidermal growth factor receptor and Mitogen-activated protein kinase kinase (MEK) inhibitors are being intensively studied and appear to be promising. Further understanding of the molecular mechanism in mTOR signaling network is needed to develop optimized therapeutic regimens. In this paper, oncogenic gene alterations in colorectal cancer, as well as their interaction with the mTOR pathway, are systematically summarized. The most recent preclinical and clinical anticancer therapeutic endeavors are reviewed. New players in mTOR signaling pathway, such as non-steroidal anti-inflammatory drug and metformin with therapeutic potentials are also discussed here.

Targeting cell death signaling in colorectal cancer: Current strategies and future perspectives

The evasion from controlled cell death induction has been considered as one of the hallmarks of cancer cells. Defects in cell death signaling are a fundamental phenomenon in colorectal cancer. Nearly any non-invasive cancer treatment finally aims to induce cell death. However, apoptosis resistance is the major cause for insufficient therapeutic success and disease relapse in gastrointestinal oncology. Various compounds have been developed and evaluated with the aim to meet with this obstacle by triggering cell death in cancer cells. The aim of this review is to illustrate current approaches and future directions in targeting cell death signaling in colorectal cancer. The complex signaling network of apoptosis will be demonstrated and the “druggability” of targets will be identified. In detail, proteins regulating mitochondrial cell death in colorectal cancer, such as Bcl-2 and survivin, will be discussed with respect to potential therapeutic exploitation. Death receptor signaling and targeting in colorectal cancer will be outlined. Encouraging clinical trials including cell death based targeted therapies for colorectal cancer are under way and will be demonstrated. Our conceptual understanding of cell death in cancer is rapidly emerging and new types of controlled cellular death have been identified. To meet this progress in cell death research, the implication of autophagy and necroptosis for colorectal carcinogenesis and therapeutic approaches will also be depicted. The main focus of this topic highlight will be on the revelation of the complex cell death concepts in colorectal cancer and the bridging from basic research to clinical use.

Methods of overcoming treatment resistance in colorectal cancer

Metastatic colorectal cancer remains a lethal disease with a poor prognosis in the majority of patients. Multiple drug combinations have been developed in recent years that have significantly improved response rates and overall survival however resistance to these drugs is inevitable. Novel agents are currently being developed and participation in clinical trials should be encouraged. In the absence of other treatment options in a patient with good performance status, there is compelling evidence for re-challenging with previously administered agents in different combinations. The aim of this review is to discuss mechanisms of resistance and methods to overcome treatment resistance in patients with metastatic colorectal cancer who are refractory to 5-FU, irinotecan, oxaliplatin, cetuximab and bevacizumab therapy.