Chemotherapeutic and targeted biological agents for metastatic bladder cancer: a comprehensive review

RNA modifications in pulmonary diseases

Threatening public health, pulmonary disease (PD) encompasses diverse lung injuries like chronic obstructive PD, pulmonary fibrosis, asthma, pulmonary infections due to pathogen invasion, and fatal lung cancer. The crucial involvement of RNA epigenetic modifications in PD pathogenesis is underscored by robust evidence. These modifications not only shape cell fates but also finely modulate the expression of genes linked to disease progression, suggesting their utility as biomarkers and targets for therapeutic strategies. The critical RNA modifications implicated in PDs are summarized in this review, including N6-methylation of adenosine, N1-methylation of adenosine, 5-methylcytosine, pseudouridine (5-ribosyl uracil), 7-methylguanosine, and adenosine to inosine editing, along with relevant regulatory mechanisms. By shedding light on the pathology of PDs, these summaries could spur the identification of new biomarkers and therapeutic strategies, ultimately paving the way for early PD diagnosis and treatment innovation.

RNA Modifications and Epigenetics in Modulation of Lung Cancer and Pulmonary Diseases

Lung cancer is the leading cause of cancer-related mortality worldwide, and its tumorigenesis involves the accumulation of genetic and epigenetic events in the respiratory epithelium. Epigenetic modifications, such as DNA methylation, RNA modification, and histone modifications, have been widely reported to play an important role in lung cancer development and in other pulmonary diseases. Whereas the functionality of DNA and chromatin modifications referred to as epigenetics is widely characterized, various modifications of RNA nucleotides have recently come into prominence as functionally important. N6-methyladosine (m6A) is the most prevalent internal modification in mRNAs, and its machinery of writers, erasers, and readers is well-characterized. However, several other nucleotide modifications of mRNAs and various noncoding RNAs have also been shown to play an important role in the regulation of biological processes and pathology. Such epitranscriptomic modifications play an important role in regulating various aspects of RNA metabolism, including transcription, translation, splicing, and stability. The dysregulation of epitranscriptomic machinery has been implicated in the pathological processes associated with carcinogenesis including uncontrolled cell proliferation, migration, invasion, and epithelial-mesenchymal transition. In recent years, with the advancement of RNA sequencing technology, high-resolution maps of different modifications in various tissues, organs, or disease models are being constantly reported at a dramatic speed. This facilitates further understanding of the relationship between disease development and epitranscriptomics, shedding light on new therapeutic possibilities. In this review, we summarize the basic information on RNA modifications, including m6A, m1A, m5C, m7G, pseudouridine, and A-to-I editing. We then demonstrate their relation to different kinds of lung diseases, especially lung cancer. By comparing the different roles RNA modifications play in the development processes of different diseases, this review may provide some new insights and offer a better understanding of RNA epigenetics and its involvement in pulmonary diseases.

Epitranscriptomics and epiproteomics in cancer drug resistance: therapeutic implications

Drug resistance is a major hurdle in cancer treatment and a key cause of poor prognosis. Epitranscriptomics and epiproteomics are crucial in cell proliferation, migration, invasion, and epithelial–mesenchymal transition. In recent years, epitranscriptomic and epiproteomic modification has been investigated on their roles in overcoming drug resistance. In this review article, we summarized the recent progress in overcoming cancer drug resistance in three novel aspects: (i) mRNA modification, which includes alternative splicing, A-to-I modification and mRNA methylation; (ii) noncoding RNAs modification, which involves miRNAs, lncRNAs, and circRNAs; and (iii) posttranslational modification on molecules encompasses drug inactivation/efflux, drug target modifications, DNA damage repair, cell death resistance, EMT, and metastasis. In addition, we discussed the therapeutic implications of targeting some classical chemotherapeutic drugs such as cisplatin, 5-fluorouridine, and gefitinib via these modifications. Taken together, this review highlights the importance of epitranscriptomic and epiproteomic modification in cancer drug resistance and provides new insights on potential therapeutic targets to reverse cancer drug resistance.

Temozolomide toxicity operates in a xCT/SLC7a11 dependent manner and is fostered by ferroptosis

The glutamate exchanger xCT (SLC7a11) is causally linked with the malignancy grade of brain tumors and represents a key player in glutamate, cystine and glutathione metabolism. Although blocking xCT is not cytotoxic for brain tumors, xCT inhibition disrupts the neurodegenerative and microenvironment-toxifying activity of gliomas. Here, we report on the use of various xCT inhibitors as single modal drugs and in combination with the autophagy-inducing standard chemotherapeutic agent temozolomide (Temodal/Temcad®, TMZ). xCT overexpressing cells (xCT^OE) are more resistant to the FDA and EMA approved drug sulfasalazine (Azulfidine/Salazopyrin/Sulazine®, SAS) and RNAi-mediated xCT knock down (xCT^KD) in gliomas increases the susceptibility towards SAS in rodent gliomas. In human gliomas, challenged xCT expression had no impact on SAS-induced cytotoxicity. Noteworthy, other xCT inhibitors such as erastin and sorafenib showed enhanced efficacy on xCT^KD gliomas. In contrast, cytotoxic action of TMZ operates independently from xCT expression levels on rodent gliomas. Human glioma cells with silenced xCT expression display higher vulnerability towards TMZ alone as well as towards combined TMZ and SAS. Hence, we tested the partial xCT blockers and ferroptosis inducing agents erastin and sorafenib (Nexavar®, FDA and EMA-approved drug for lung cancer). Noteworthy, xCT^OE gliomas withstand erastin and sorafenib-induced cell death in a concentration-dependent manner, whereas siRNA-mediated xCT knock down increased susceptibility towards erastin and sorafenib. TMZ efficacy can be potentiated when combined with erastin, however not by sorafenib. Moreover, gliomas with high xCT expression are more vulnerable towards combinatorial treatment with erastin-temozolomide. These results disclose that ferroptosis inducers are valid compounds for potentiating the frontline therapeutic agent temozolomide in a multitoxic approach.

Effect of Neoadjuvant Chemotherapy on Renal Function following Radical Cystectomy: Is there a Meaningful Impact?

Objective: To evaluate the patterns of impact of neoadjuvant chemotherapy (NAC) on renal function across the initial year following treatment for muscle-invasive bladder cancer (MIBC) with radical cystectomy (RC). Methods: We reviewed the charts of 241 patients who underwent RC for urothelial carcinoma of the bladder between 2003-14 at our institution. Renal function was evaluated at multiple time points (pre-chemotherapy, pre-operatively, post-operatively, 6-12 months follow-up), and then classified by CKD staging. Univariable and multivariable logistic regression analyses were performed to determine relationship between NAC and change in CKD stage. Results: Of the 241 patients who underwent RC for urothelial carcinoma of the bladder, 66 (27%) received NAC and 175 (73%) did not. In multivariable analysis, NAC was significantly associated with a decrease of at least one CKD stage from baseline to post-op (p = 0.009), but not to the 6-12 months follow-up time point (p = 0.050). The loss of GFR in the NAC cohort occurs up-front with chemotherapy, but the peri-operative course is similar to those who underwent cystectomy alone. Of the 15 NAC patients (26.8%) who were Stage 3 CKD prior to chemotherapy, none progressed to a higher stage CKD. Conclusion: NAC is associated with an initial decline in GFR, which then remains stable through the first year following RC. Despite an initial insult, patients receiving NAC are not vulnerable to further deterioration. When appropriately selected, NAC does not appear to result in a clinically significant deterioration of renal function.

Emerging role of immunotherapy in urothelial carcinoma-Future directions and novel therapies

Tremendous advances in our understanding of the tumor immunology and molecular biology of urothelial carcinoma (UC) have led to the recent approval of immunotherapy as a novel option for patients with UC with advanced disease. Despite the promising data of novel immune checkpoint inhibitors, only a small subset of patients with UC achieves durable remissions. Because an optimal antitumor response requires coordination of multiple immune, tumor, and microenvironment effector cells, novel approaches targeting distinct mechanisms of action likely in combination are needed. In addition, discovery of reliable immune biomarkers, understanding of mechanisms of resistance, and novel clinical trial designs are warranted for maximum benefit of UC immunotherapy.

Solid lipid nanoparticles co-loaded with doxorubicin and α-tocopherol succinate are effective against drug-resistant cancer cells in monolayer and 3-D spheroid cancer cell models

This work aimed to develop solid lipid nanoparticles (SLN) co-loaded with doxorubicin and α-tocopherol succinate (TS) and to evaluate its potential to overcome drug resistance and to increase antitumoral effect in MCF-7/Adr and NCI/Adr cancer cell lines. The SLN were prepared by a hot homogenization method and characterized for size, zeta potential, entrapment efficiency (EE), and drug loading (DL). The cytotoxicity of SLN or penetration was evaluated in MCF-7/Adr and NCI/adr as a monolayer or spheroid cancer cell model. The SLN showed a size in the range of 74-80nm, negative zeta potential, EE of 99%, and DL of 67mg/g. The SLN co-loaded with Dox and TS showed a stronger cytotoxicity against MCF-7/Adr and NCI/Adr cells. In the monolayer model, the doxorubicin co-localization as a free and encapsulated form was higher for the encapsulated drug in MCF-7/Adr and NCI/adr, suggesting a bypassing of P-glycoprotein bomb efflux. For cancer cell spheroids, the SLN co-loaded with doxorubicin and TS showed a prominent cytotoxicity and a greater penetration of doxorubicin.

Epidermal growth factor receptor inhibitor with fluorouracil, leucovorin, and irinotecan as an alternative treatment for advanced upper tract urothelial carcinoma: a case report

Background

Currently, there is no standard salvage regimen after the failure of cisplatin-based chemotherapy for advanced urothelial carcinoma. The combination of epidermal growth factor receptor inhibitor with fluorouracil, leucovorin, and irinotecan was originally designed for the treatment of metastatic colorectal cancer. Until now, there have been no reports using this combination therapy in treating advanced upper tract urothelial carcinoma. To the best of our knowledge, this is the first report showing this possible treatment regimen for advanced upper tract urothelial carcinoma.

Case presentation

We report the case of a 90-year-old Chinese woman who was diagnosed with metastatic colorectal cancer and urothelial carcinoma of the bladder, ureter, and renal pelvis. The upper tract urothelial carcinoma was well controlled by the chemotherapy regimen for metastatic colorectal cancer. Considering her age, we used only laser ablation for the treatment of her urothelial carcinoma in combination with intravesical mitomycin C chemotherapy. Follow-up cystoscopy and ureterorenoscopy showed an unexpected regression of the upper tract urothelial tumor. Contrast-enhanced computed tomography also demonstrated the same results.

Conclusions

This novel regimen for the treatment of upper tract urothelial carcinoma may merit further investigation or evaluation in clinical trials.

Electronic supplementary material

The online version of this article (doi:10.1186/s13256-016-0879-6) contains supplementary material, which is available to authorized users.

Human Neural Stem Cells Overexpressing a Carboxylesterase Inhibit Bladder Tumor Growth

Bladder cancer is a significant clinical and economic problem. Despite intravesical chemotherapy and immunotherapy, up to 80% of patients with non-muscle-invasive bladder cancer develop recurrent tumors, of which 20% to 30% evolve into more aggressive, potentially lethal tumors. Recently, bladder cancer cells are considered to be mediators of resistance to current therapies and therefore represent strong candidates as biologic targets. No effective chemotherapy has yet been developed for advanced bladder cancer. It is desirable that a drug can be delivered directly and specifically to bladder cancer cells. Stem cells have selective migration ability toward cancer cells, and therapeutic genes can be easily transduced into stem cells. In suicide gene therapy for cancer, stem cells carry a gene encoding a carboxylesterase (CE) enzyme that transforms an inert CPT-11 prodrug into a toxic SN-38 product, a topoisomerase 1 inhibitor. In immunodeficient mice, systemically transplanted HB1.F3.CE stem cells migrated toward the tumor implanted by the TCCSUP bladder cancer cell line, and, in combination with CPT-11, the volume of tumors was significantly reduced. These findings may contribute to the development of a new selective chemotherapeutic strategy against bladder cancer. Mol Cancer Ther; 15(6); 1201-7. ©2016 AACR.

HIF-1α/MDR1 pathway confers chemoresistance to cisplatin in bladder cancer

Bladder cancer (BCa) is the 9th most common malignant tumor and the 13th leading cause of death due to cancer. The development of surgery and target drugs bring new challenges for the traditional concept for BCa therapy, and chemotherapy is still the final option for many BCa patients, and cisplatin-containing regimen the most effective one. However, the ubiquitous application of cisplatin-containing regimen in BCa results in the cisplatin-resistance, in addition, the cisplatin‑resistant BCa manifests enhanced malignant behavior, the mechanism of which is unclear. In the present study, we used BCa cell lines to to clarify this point. BCa cell lines T24/J82 were pretreated with cisplatin >3 months to construct stable cisplatin-resistant cell lines (tagged T24(Cis-R) and J82(Cis-R)), which manifested as enhanced capacity of proliferation and malignant behavior in vivo and in vitro, accompanied by cisplatin, and even doxorubicin resistance. The following mechanism dissection revealed that prolonged treatment time of T24/J82 cells led to elevated expression of HIF-1α, which targeted the increased expression of MDR1 on the one hand, and contributed to BCa cell proliferation, migration/invasion on the other hand. Finally, IHC staining of human BCa tissue supported our conclusion that the expression of HIF-1α and MDR1 was higher in chemoresistant tissue vs. chemosensitive tissue. Our results provided a new view of HIF-1α in chemotherapy.

Cisplatin and Paclitaxel Alter the Expression Pattern of miR-143/145 and miR-183/96/182 Clusters in T24 Bladder Cancer Cells

Although cisplatin-based chemotherapy is considered to be the treatment of choice for metastatic bladder cancer, its efficacy and tolerability has proven to be limited. MicroRNAs are small noncoding RNAs, whose genes are frequently organized in clusters. These molecules constitute posttranscriptional regulators of mRNA expression and are claimed to be deregulated in cancer. miR-143/145 and miR-183/96/182 clusters have been extensively studied in bladder cancer cells. Herein, we tried to add up to this knowledge by assessing the expression levels of the five mature microRNAs derived from the aforementioned clusters in T24 bladder cancer cells exposed to either cisplatin or paclitaxel. For both compounds, the viability of treated T24 cells was estimated via the MTT colorimetric assay and the Trypan Blue exclusion method, while a fraction of the cells was left to recover. The expression levels of all mature microRNAs were finally quantified both in treated and in recovered cells by performing real-time PCR. According to our data, cisplatin and paclitaxel strongly decreased T24 cells' viability, showing in parallel the ability to significantly down-regulate miR-143 levels, and up-regulate the expression levels of miR-145, miR-183, miR-96, and miR-182, which, in their total, demonstrated case-specific variations after recovery period.

MLN4924 Synergistically Enhances Cisplatin-induced Cytotoxicity via JNK and Bcl-xL Pathways in Human Urothelial Carcinoma

Cisplatin-based chemotherapy is the primary treatment for metastatic bladder urothelial carcinoma. However, the response rate is only 40–65%. This study investigated the anti-tumor effect and underlying mechanisms of the combination of cisplatin and the NEDD8-activating enzyme inhibitor MLN4924 in human bladder urothelial carcinoma. The combination of cisplatin and MLN4924 exerted synergistic cytotoxicity on two high-grade bladder urothelial carcinoma cell lines, NTUB1 and T24 (combination index <1). MLN4924 also potentiated the cisplatin-induced apoptosis and activation of caspase-3 and -7, phospho-histone H2A.X and PARP. c-Jun N-terminal kinase (JNK) activation and a down-regulation of B-cell lymphoma-extra large (Bcl-xL) were also observed during cisplatin and MLN4924 treatment. Inhibition of JNK activation partially restored cell viability and Bcl-xL expression. Bcl-xL overexpression also rescued cell viability. MLN4924 significantly potentiated cisplatin-induced tumor suppression in urothelial carcinoma xenograft mice. In summary, MLN4924 synergistically enhanced the anti-tumor effect of cisplatin via an increase in DNA damage, JNK activation and down-regulation of Bcl-xL in urothelial carcinoma cells. These findings provide a new therapeutic strategy for the treatment of bladder cancer.

Results from a Phase I Study of Lapatinib with Gemcitabine and Cisplatin in Advanced or Metastatic Bladder Cancer: EORTC Trial 30061

BACKGROUND/OBJECTIVE

Lapatinib is a potent HER1 and HER2 inhibitor. Gemcitabine-cisplatin (GC) is a standard chemotherapy regimen for advanced/metastatic bladder cancer. This phase I study examined the safety of lapatinib in combination with GC in patients with bladder cancer. The primary aim was to determine the maximum tolerated dose (MTD) of lapatinib in combination with GC.

METHODS

A 3 + 3 dose escalation protocol was used with lapatinib at 750, 1,000 and then 1,250 mg. It was dosed daily with gemcitabine (1,000 mg/m2 on days 1, 8 and 15) and cisplatin (70 mg/m2 on day 2) every 28 days. In all, 18 patients with a median age of 63 years (range 50-77) were included; 3/6, 3/5 and 6/7 patients received lapatinib at 750, 1,000 and 1,250 mg, combined with GC, in cohorts 1, 2 and 3, respectively.

RESULTS

No dose-limiting toxicities (DLTs) were observed in cohort 1 or 2 (3 patients each); in cohort 3 (2 × 3 patients), 1 of the 6 patients presented DLTs (grade 4, treatment-related febrile neutropenia and renal failure). Twelve patients received 6 cycles.

CONCLUSIONS

Lapatinib at 750-1,250 mg combined with GC appears safe and tolerable. The MTD of lapatinib combined with GC in bladder cancer was 1,250 mg.

Safety and efficacy of combination therapy with low-dose gemcitabine, paclitaxel, and sorafenib in patients with cisplatin-resistant urothelial cancer

Various regimens including molecular targeted agents have been examined in patients with cisplatin (CDDP)-resistant urothelial cancer (UC). However, some studies have been stopped owing to the development of severe adverse events. The main aim of this study was to examine the anticancer effects, changes in the quality of life (QoL), and safety of combined therapy of low-dose gemcitabine, paclitaxel, and sorafenib (LD-GPS) in patients with CDDP-resistant UC. Twenty patients were treated with gemcitabine (700 mg/m(2) on day 1), paclitaxel (70 mg/m(2) on day 1), and sorafenib (400 mg/day on days 8-22). QoL and pain relief were evaluated using the short-form survey (SF)-36 for bodily pain and the visual analog scale (VAS). VAS scores were significantly decreased by both the second- and third-line therapies (P = 0.012 and 0.028, respectively). The bodily pain score from the SF-36 survey was also significantly (P = 0.012) decreased. Complete responses, partial responses, and stable disease were found in 0 (0.0 %), 1 (5.0 %), and 13 patients (65 %), respectively. The median (interquartile range) period of overall survival after starting of this therapy was 7 (5-11) months. Three patients (15.0 %) stopped therapy because of grade 3 fatigue and hand-foot reactions. LD-GPS therapy was well tolerated by patients with CDDP-resistant UC. QoL was maintained, and improvements in their pain levels were found after treatment; pain relief was detected after third-line therapy. We suggest that this treatment regimen is worthy of consideration as second- and third-line therapy for patients with CDDP-resistant UC.

In Vitro Biocompatibility of Surface-Modified Porous Alumina Particles for HepG2 Tumor Cells: Toward Early Diagnosis and Targeted Treatment

Porous alumina photoluminescence-inherent particles are produced and proposed for the development of biomarkers detectors and localized treatment of HepG2 cells. Nanoporous alumina particles (NPAPs) are amorphous, consist of hexagonally ordered nanometric pores in an alumina matrix, have high chemical stability in physiological pH, and exhibit a high inherent photoluminescence in the visible spectrum independently of their size, selectable from nanometers to tens of micrometers. The surface of NPAPs is chemically modified using two different functionalization methods, a multistep method with (3-aminopropyl)triethoxysilane (APTES) and glutaraldehyde (GLTA) and a novel simplified-step method with silane-PEG-NHS. Fourier Transform infrared spectroscopy analysis confirmed the proper surface modification of the particles for both functionalization methods. HepG2 cells were cultured during different times with growing concentrations of particles. The analysis of cytotoxicity and cell viability of HepG2 cells confirmed the good biocompatibility of NPAPs in all culture conditions. The results prove the suitability of NPAPs for developing new label-free biomarker detectors and advantageous carriers for localized drug delivery.

Fractionated intravesical radioimmunotherapy with (213)Bi-anti-EGFR-MAb is effective without toxic side-effects in a nude mouse model of advanced human bladder carcinoma

Gold standard in therapy of superficial, non-muscle invasive urothelial tumors is transurethral resection followed by intravesical instillation therapies. However, relapse is commonly observed and therefore new therapeutic approaches are needed. Application of (213)Bi-immunoconjugates targeting EGFR had shown promising results in early tumor stages. The aim of this study was the evaluation of fractionated application of (213)Bi-anti-EGFR-MAb in advanced tumor stages in a nude mouse model. Luciferase-transfected EJ28 human bladder carcinoma cells were instilled intravesically into nude mice following electrocautery. Tumor development was monitored via bioluminescence imaging. One day after tumor detection mice were treated intravesically either 2 times with 0.93 MBq or 3 times with 0.46 MBq of (213)Bi-anti-EGFR-MAb. Therapeutic efficacy was evaluated via overall survival and toxicity toward normal urothelium by histopathological analysis. Mice without treatment and those treated with the native anti-EGFR-MAb showed mean survivals of 65.4 and 57.6 d, respectively. After fractionated treatment with 0.93 MBq of (213)Bi-anti-EGFR-MAb animals reached a mean survival of 141.5 d and 33% of the animals survived at least 268 d. Fractionated treatment with 0.46 MBq (213)Bi-anti-EGFR-MAb resulted in a mean survival of 131.8 d and 30% of the animals survived longer than 300 d. Significant differences were only observed between the control groups and the group treated twice with 0.93 MBq of (213)Bi-anti-EGFR-MAb. No toxic side-effects on the normal urothelium were observed even after treatment with 3.7 MBq of (213)Bi-anti-EGFR-MAb. The study demonstrates that the fractionated intravesical radioimmunotherapy with (213)Bi-anti-EGFR-MAb is a promising approach in advanced bladder carcinoma.

Real-World Vinflunine Outcomes in Bladder Cancer in a Single-Institution Study: Moving Beyond Clinical Trials

PURPOSE

Intravenous vinflunine 320 mg/m(2) every 3 weeks plus best supportive care resulted in better overall survival in comparison with best supportive care alone for eligible patients with failure of prior therapy with locally advanced or metastatic transitional cell cancer of urothelial tract (TCCU). The objective of the present study was to describe our real-life experience of vinflunine for treatment of patients with TCCU.

PATIENTS AND METHODS

We retrospectively investigated all patients with TCCU who received at least 1 cycle of vinflunine.

RESULTS

Nineteen patients were treated between May 2010 and March 2014 in a compassionate-use program. Performance status was poor in our real-life cohort, with 6 patients (32%) with an Eastern Cooperative Oncology Group performance status of 2. Median duration of vinflunine treatment was 2.4 months (range, 0-4.3 months), and median number of cycles was 3 (range, 1-6). Total response rate was 32%, with partial responses only. Disease control rate was 53%, with a median duration of 7.7 months (range, 6.0-9.4 months). Median progression-free survival was 87 days, or 2.9 months (range, 0.7-11.7 months). After vinflunine treatment, 42% of patients received from 1 to 3 additional lines of chemotherapy. The most frequent grade 4 toxicities were constipation (26%), with 3 intestinal obstructions (16%) and 1 mechanical ileus (5%); and asthenia and fatigue (21%).

CONCLUSION

Vinflunine, as a TCCU second-line chemotherapy, brings benefits, particularly in cases where there is no alternative treatment.

Targeting glycogen metabolism in bladder cancer

Metabolism has been a heavily investigated topic in cancer research for the past decade. Although the role of aerobic glycolysis (the Warburg effect) in cancer has been extensively studied, abnormalities in other metabolic pathways are only just being understood in cancer. One such pathway is glycogen metabolism; its involvement in cancer development, particularly in urothelial malignancies, and possible ways of exploiting aberrations in this process for treatment are currently being studied. New research shows that the glycogen debranching enzyme amylo-α-1,6-glucosidase, 4-α-glucanotransferase (AGL) is a novel tumour suppressor in bladder cancer. Loss of AGL leads to rapid proliferation of bladder cancer cells. Another enzyme involved in glycogen debranching, glycogen phosphorylase, has been shown to be a tumour promoter in cancer, including in prostate cancer. Studies demonstrate that bladder cancer cells in which AGL expression is lost are more metabolically active than cells with intact AGL expression, and these cells are more sensitive to inhibition of both glycolysis and glycine synthesis--two targetable pathways. As a tumour promoter and enzyme, glycogen phosphorylase can be directly targeted, and preclinical inhibitor studies are promising. However, few of these glycogen phosphorylase inhibitors have been tested for cancer treatment in the clinical setting. Several possible limitations to the targeting of AGL and glycogen phosphorylase might also exist.