Pioglitazone and oral cancer risk in patients with type 2 diabetes

Pioglitazone and breast cancer risk in female patients with type 2 diabetes mellitus: a retrospective cohort analysis

Background

Whether pioglitazone may affect breast cancer risk in female diabetes patients is not conclusive and has not been investigated in the Asian populations.

Methods

The reimbursement database of Taiwan’s National Health Insurance was used to enroll an unmatched cohort and a propensity score-matched cohort of ever users and never users of pioglitazone in female patients with newly diagnosed type 2 diabetes during 1999–2008. The patients were alive on January 1, 2009 and were followed up for breast cancer incidence until December 31, 2011. Cox regression was used to estimate hazard ratios for ever users and tertiles of cumulative duration of pioglitazone therapy versus never users, and for cumulative duration of pioglitazone therapy treated as a continuous variable. Three models were created for the unmatched cohort and the matched cohort, respectively: 1) without adjustment for covariates; 2) after adjustment for covariates that differed with statistical significance (P-value < 0.05) between ever users and never users; and 3) after adjustment for all covariates.

Results

There were 174,233 never users and 6926 ever users in the unmatched cohort; and 6926 never users and 6926 ever users in the matched cohort. After a median follow-up of 2.8 years, the numbers of incident breast cancer were 1044 in never users and 35 in ever users in the unmatched cohort and were 41 and 35, respectively, in the matched cohort. Hazard ratios suggested a null association between pioglitazone and breast cancer in all three models in either the unmatched cohort or the matched cohort. The overall hazard ratio after adjustment for all covariates was 0.758 (95% confidence interval: 0.539–1.065) in the unmatched cohort and was 0.824 (95% confidence interval: 0.524–1.296) in the matched cohort. None of the hazard ratios for the tertiles of cumulative duration of pioglitazone therapy and for the cumulative duration being treated as a continuous variable were statistically significant.

Conclusions

This study suggests a null association between pioglitazone and breast cancer risk in female patients with type 2 diabetes mellitus. However, because of the small breast cancer cases and the limited follow-up time, further studies are warranted to confirm our findings.

Diabetes and its Potential Impact on Head and Neck Oncogenesis

In recent years, the incidence of diabetes mellitus and cancer has increased sharply; indeed, these have become the two most important diseases threatening health and survival. Head and neck (HN) tumors are the sixth most common malignancies in humans. Numerous studies have shown that there are many common risk factors for diabetes mellitus and HN squamous cell carcinoma, including advanced age, poor diet and lifestyle, and environmental factors. However, the mechanism linking the two diseases has not been identified. A number of studies have shown that diabetes affects the development, metastasis, and prognosis of HN cancer, potentially through the associated hyperglycemia, hyperinsulinemia and insulin resistance, or chronic inflammation. More recent studies show that metformin, the first-line drug for the treatment of type 2 diabetes, can significantly reduce the risk of HN tumor development and reduce mortality in diabetic patients. Here, we review recent progress in the study of the relationship between diabetes mellitus and HN carcinogenesis, and its potential mechanisms, in order to provide a scientific basis for the early diagnosis and effective treatment of these diseases.

Association between pioglitazone use and head and neck cancer: Population-based case-control study

BACKGROUND

This study aimed to evaluate the association between pioglitazone use and the occurrence of head and neck cancer.

METHODS

Data for this case-control study were retrieved from the Taiwan National Health Insurance Research Database. A total of 21 464 diabetic patients newly diagnosed with head and neck cancers were identified. We used propensity score matching to select 64 392 comparison patients (3:1 ratio). Multiple logistic regression modeling was used to examine the association of head and neck cancer with pioglitazone use in the 5 years preceding the cancer diagnosis.

RESULTS

Bivariate analysis showed a significant difference in the prevalence of prior using pioglitazone between cases and controls (19.3% vs 18.5%, P < .001) was observed. Multiple regression analysis showed adjusted odds of pioglitazone use of 1.06 (95% CI: 1.02-1.10) among cases relative to controls.

CONCLUSIONS

Prior pioglitazone use was associated with oral cavity cancer.

Evidence that peroxisome proliferator-activated receptor γ suppresses squamous carcinogenesis through anti-inflammatory signaling and regulation of the immune response

A variety of evidence suggests that peroxisome proliferator-activated receptor (PPAR)γ agonists may represent a potential pharmacologic target in the prevention or treatment of skin cancer. In particular, recent reports suggest that PPARγ activation may exert at least some of its anti-neoplastic effects through the suppression of tumor promoting chronic inflammation as well as by strengthening antitumor immune responses. This activity is thought to occur through a distinct mode of ligand interaction with PPARγ that causes transrepression of transcription factors that are involved in inflammatory and immunomodulatory signaling. However, current thiazolidinedione (TZD)-type PPARγ agonists have significant safety concerns that limit their usefulness as a preventive or therapeutic option. Due to the relatively large ligand binding pocket of PPARγ, a diverse group of ligands can be seen to interact with distinct modes of binding to PPARγ, leading to the phenomenon of partial agonist activity and selective PPARγ modulators (SPPARγM). This has led to the development of ligands that are tailored to deliver desired pharmacologic activity, but lack some of the negative side effects associated with full agonists, such as the currently utilized TZD-type PPARγ agonists. In addition, there is evidence that a number of phytochemicals that are currently being touted as antineoplastic nutraceuticals also possess PPARγ activity that may partially explain their pharmacologic activity. We propose that one or more of these partial agonists, SPPARγMs, or putative phytochemical PPARγ ligands could presumably be used as a starting point to design more efficacious anti-neoplastic PPARγ ligands that lack adverse pharmacological effects.

Global and Regional Effects of Bladder Cancer Risk Associated with Pioglitazone Therapy in Patients with Diabetes

It has been debated for several years as to whether the antidiabetic drug pioglitazone increases the risk for bladder cancer. A series of recent large population studies yielded conflicting results. To investigate why the observational studies yielded conflicting results, we conducted stratified analyses to analyze the potential confounders behind these discordant outcomes. A total of 2,764,731 participants from observational (OB) studies and 9,999 from randomized control trials (RCTs) were identified for these analyses. The stratified analysis revealed that the study type, adjustment for age/sex, treatment duration, cumulative dose, agents used in a control group, mean period of follow-up and study population region might contribute to the discordant outcomes. In terms of population regions, pioglitazone increased the risk for bladder cancer could be found in European population, and patients who undergo treatment with pioglitazone for longer durations (>12 months) or are administrated a larger cumulative dose (>28,000 mg) might require more attention, and the long-term effects (≥3.6 years) of pioglitazone needs be monitored more carefully.

Sitagliptin and oral cancer risk in type 2 diabetes patients

The reimbursement database of the Taiwan’s National Health Insurance was used to evaluate oral cancer risk after sitagliptin use. Patients newly diagnosed of type 2 diabetes during 1999–2008 were recruited. A 1:1 propensity score matched-pair sample of 39195 ever users and 39195 never users were followed up until December 31, 2011. Cox regression incorporated with the inverse probability of treatment weighting using propensity score was used to estimate hazard ratios. Results showed that the overall hazard ratio was not statistically significant (0.956, 95% confidence interval: 0.652–1.401). However, in tertile analyses, the hazard ratio for the first (< 7.47 months), second (7.47–15.63 months) and third (> 15.63 months) tertile of cumulative duration was 1.563 (0.963–2.537), 1.236 (0.738–2.071) and 0.345 (0.164–0.725), respectively; and was 1.575 (0.963–2.575), 1.224 (0.738–2.033) and 0.347 (0.165–0.731), respectively, for the first (< 19,600 mg), second (19,600–42,200 mg) and third (> 42,200 mg) tertile of cumulative dose. Sensitivity analyses after excluding patients who developed any other cancer during follow-up did not change the results substantially. Additionally, the risk of oral diseases that may predispose to oral cancer (i.e., “gingival and periodontal diseases" and/or "oral mucosal lesions") paralleled the risk pattern of oral cancer, suggesting a possible explanation for the risk change of oral cancer related to sitagliptin. In conclusion, sitagliptin may reduce oral cancer risk when the cumulative duration is > 15.63 months or the cumulative dose is > 42,200 mg.

Deciphering the Roles of Thiazolidinediones and PPAR in Bladder Cancer

The use of thiazolidinedione (TZD) therapy in type II diabetic patients has proven useful in the lowering of blood glucose levels. However, recent investigations have shown that there may be potential health concerns associated, including the risk of developing bladder cancer as well as complications in the cardiovasculature. TZDs are ligands for the nuclear receptor PPARγ, and activation causes lipid uptake and insulin sensitization, both of which are critical processes for diabetic patients whose bodies are unable to utilize insulin effectively. Several studies have shown that PPARγ/TZDs decrease IGF-1 levels and, thus, reduce cancer growth in carcinomas such as the pancreas, colon, liver, and prostate. However, other studies have shed light on the potential of the receptor as a biomarker for uroepithelial carcinomas, particularly due to its stimulatory effect on migration of bladder cancer cells. Furthermore, PPARγ may provide the tumor-promoting microenvironment by de novo synthesis of nutrients that are needed for bladder cancer development. In this review, we closely examine the TZD class of drugs and their effects on PPARγ in patient studies along with additional molecular factors that are positive modulators, such as protein phosphatase 5 (PP5), which may have considerable implications for bladder cancer therapy.

Metformin may reduce oral cancer risk in patients with type 2 diabetes

BACKGROUND

Whether metformin use may affect the risk of oral cancer required further investigation.

METHODS

The reimbursement database of the National Health Insurance in Taiwan was used. Patients with type 2 diabetes mellitus at an onset age of 25-74 years during 1999-2005 and newly treated with either metformin (n = 288198, "ever users of metformin") or other antidiabetic drugs (n = 16263, "never users of metformin") were followed for at least 6 months for oral cancer until December 31, 2011. The treatment effect of metformin (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression adjusted for propensity score (PS) or incorporated with the inverse probability of treatment weighting (IPTW) using PS.

RESULTS

The respective numbers of incident oral cancer in ever users and never users were 1273 (0.44%) and 119 (0.73%), with respective incidences of 92.7 and 163.6 per 100,000 person-years. The overall hazard ratios (95% confidence intervals) suggested a significantly lower risk [0.584 (0.483-0.707) for PS-adjusted model, and 0.562 (0.465-0.678) for IPTW model]. In tertile analyses, the PS-adjusted hazard ratios (95% confidence intervals) for the first (<21.5 months), second (21.5-45.9 months) and third (>45.9 months) tertile of cumulative duration were 1.403 (1.152-1.708), 0.557 (0.453-0.684) and 0.152 (0.119-0.194), respectively; and were 1.244 (1.024-1.511), 0.526 (0.429-0.645) and 0.138 (0.108-0.176), respectively, for IPTW.

CONCLUSIONS

Metformin may significantly reduce the risk of oral cancer, especially when the cumulative duration is more than 21.5 months.

Metformin in combination with 5-fluorouracil suppresses tumor growth by inhibiting the Warburg effect in human oral squamous cell carcinoma

Cancer cells show enhanced glucose consumption and lactate production even in the presence of abundant oxygen, a phenomenon known as the Warburg effect, which is related to tumor proliferation, progression and drug-resistance in cancers. Hypoxia-inducible factor-1 (HIF-1) and several members of Phosphatidylinositol-4, 5-bisphosphate 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway positively contribute to the Warburg effect, whereas AMP activated protein Kinase (AMPK) acts as a negative regulator. Targeting the regulator molecules of Warburg effect might be a useful strategy to effectively kill cancer cells. Metformin was reported to be effective against various cancers as it inhibits cell proliferation by activating AMPK, and inhibiting mTOR and HIF-1α. Several studies suggested the efficacy of metformin with 5-fluorouracil (5-FU) against esophageal and colon cancer. In this study, we evaluated the efficacy of metformin and 5-FU combined therapy against human oral squamous cell carcinoma (OSCC) in vitro and in vivo. MTT assay and TUNEL assay revealed that metformin (4 mg/ml) and 5-FU (2.5 µg/ml) combination treatment effectively inhibited cell growth and induced apoptosis in OSCC cell lines (HSC2, HSC3 and HSC4) compared to either agent alone. Lactate colorimetric assay detected decreased level of lactate in the supernatants of metformin and 5-FU treated cells compared to cells treated with metformin or 5-FU. Western blot analysis showed marked downregulation of HIF-1α and mTOR expression, and upregulation of AMPKα in cells treated with metformin and 5-FU combination treatment. Combination therapy with metformin (200 mg/kg, i.p.) and 5-FU (10 mg/kg, i.p.) for 4 weeks (5 days/week) effectively reduced HSC2 tumor growth (77.6%) compared to metformin (59.9%) or 5-FU (52%) alone in nude mice. These findings suggest that metformin and 5-FU combined therapy could exert strong antitumor effect against OSCC through the inhibition of Warburg phenomenon in tumor cells.

Dynamic cellular and molecular modulations of diabetes mediated head and neck carcinogenesis

Head and neck squamous cell carcinoma (HNSCC) is one of the most prevalent neoplasms worldwide. While numerous potent dietary insults were considered as oncogenic players for HNSCC development, the impact of metabolic imbalance was less emphasized during HNSCC carcinogenesis. Previous preclinical and epidemiological investigations showed that DM could possibly be correlated with greater incidence and poorer prognosis in HNSCC patients; however, the outcomes from different groups are contradictive and underlying mechanisms remains elusive. In the present study, the changes of cellular malignancy in response to prolonged glucose incubation in HNSCC cells were examined. The results demonstrated that hyperglycemia enhanced HNSCC cell malignancy over time through suppression of cell differentiation, promotion of cell motility, increased resistance to cisplatin, and up-regulation of the nutrient-sensing Akt/AMPK-mTORC1 pathway. Further analysis showed that a more aggressive tongue neoplastic progression was found under DM conditions compared to non-DM state whereas DM pathology led to a higher percentage of cervical lymph node metastasis and poorer prognosis in HNSCC patients. Taken together, the present study confirms that hyperglycemia and DM could enhance HNSCC malignancy and the outcomes are of great benefit in providing better anti-cancer treatment strategy for DM patients with HNSCC.

Effect of metformin on progression of head and neck cancers, occurrence of second primary cancers, and cause-specific survival

BACKGROUND

This study aimed to investigate the effect of metformin on progression of head and neck cancers, occurrence of second primary cancers, and cause-specific survival.

METHODS

This study analyzed a retrospective cohort of 1,151 consecutive patients with head and neck squamous cell carcinoma who were treated at our hospital. Patients were divided into three groups: nondiabetic, nonmetformin, and metformin. Clinical characteristics, recurrence of index head and neck cancer, occurrence of second primary cancer, and survival were compared among the different groups.

RESULTS

Of 1,151 patients, 99 (8.6%) were included in the metformin group, 79 (6.8%) were in the nonmetformin group, and 973 (84.5%) were in the nondiabetic group. Diabetic status and metformin exposure had no significant impact on index head and neck cancer recurrence or second primary cancer development (p > .2). The nonmetformin group showed relatively lower overall (p = .017) and cancer-specific (p = .054) survival rates than the other groups in univariate analyses, but these results were not confirmed in multivariate analyses.

CONCLUSION

Metformin use did not show beneficial effects on index tumor progression, second primary cancer occurrence, and cause-specific survival in patients with head and neck cancer compared with nonmetformin users and nondiabetic patients.