Cancer-Type OATP1B3 mRNA in Extracellular Vesicles as a Promising Candidate for a Serum-Based Colorectal Cancer Biomarker.

Cancer-type organic anion transporting polypeptide 1B3 (Ct-OATP1B3) mRNA is a variant isoform of the liver-type OATP1B3. Because Ct-OATP1B3 mRNA shows an excellent cancer-specific expression profile in colorectal cancer (CRC), and that its expression levels are associated with CRC prognosis, it holds the potential to become a useful CRC detection and diagnosis biomarker. While the potential is currently justified only at the tissue level, if existence of Ct-OATP1B3 mRNA in CRC-derived extracellular vesicles (EVs) is validated, the findings could enhance its translational potential as a CRC detection and diagnosis biomarker. Therefore, this study aims at proving that Ct-OATP1B3 mRNA exists in CRC-derived EVs, and can be detected using serum specimens. To examine the possibility of Ct-OATP1B3 mRNA being existed in extracellular milieu, we isolated EVs from the human CRC (HCT116, HT-29, and SW480) cell lines, and prepared their cDNAs. The RT-PCR results showed that Ct-OATP1B3 mRNA was clearly present in EVs derived from the human CRC cell lines. Then, in order to further explore the possibility that Ct-OATP1B3 mRNA in CRC-derived EVs can be detected in serum, we isolated serum EVs derived from human CRC xenograft mice, and then performed RT-PCR. The results showed that Ct-OATP1B3 mRNA could be found in all serum EV and CRC tissue samples of the mice examined. Collectively, our findings, which show that Ct-OATP1B3 mRNA exists in EVs and can be detected in (at least) mouse serum, strengthen the potential use of Ct-OATP1B3 mRNA as a serum-based CRC biomarker.

Difference of income inequalities of denture use by co-payment rates: A JAGES cross-sectional study.

OBJECTIVES: Studies suggest that wearing dentures to restore missing teeth can have a positive impact on health status. However, income inequalities in denture wearing exist. The aim of this study was to investigate how differing co-payment rates under the current Japanese Universal Health Insurance Coverage System affect income inequalities in denture non-use among older adults with severe tooth loss. METHODS: This cross-sectional study used data from the 2019 Japan Gerontological Evaluation Study (JAGES). Self-administered questionnaires were mailed to 345 356 independent people who did not receive long-term care insurance benefits and were aged ≥65 years. The dependent variable was denture non-use, and the independent variable was the equivalent annual household income. The Slope Index of Inequality (SII) and Relative Index of Inequality (RII) were used with regression-based approaches to determine both absolute and relative inequalities in denture non-use by co-payment rates. The covariates were sex, age, years of education, number of teeth and comorbidities. RESULTS: Of the 240 889 responses received (response rate =69.9%), we analysed 21 594 participants who fulfilled the inclusion criteria. The mean age was 72.8 years (standard deviation =4.1), and 57.6% were men. For 30 per cent, 20 per cent and 10 per cent co-payment rates, the percentages of people who did not use dentures and had severe tooth loss (≤9 teeth) were 18.3%, 13.3%, and 8.5%, respectively. All analyses confirmed significant inequalities in denture non-use. The lower the co-payment rate, the smaller the inequalities. SIIs for each co-payment rate were as follows: 30 per cent =13.35% (95% confidence interval [CI] = 9.61-17.09); 20 per cent =7.85% (95% CI = 4.88-10.81); and 10 per cent =4.85% (95% CI = 2.55-7.16). Inclusion of interaction term between income and co-payment rate significantly lowered the inequalities by co-payment rate in logistic regression analysis and SII. For RII, although the interaction was not statistically significant, a similar trend was observed. CONCLUSIONS: Income inequalities in denture use existed among older adults with severe tooth loss in Japan, and the inequalities appeared to be greater when the co-payment rate was higher.

Cancer-type organic anion transporting polypeptide 1B3 is a target for cancer suicide gene therapy using RNA trans-splicing technology.

Cancer-type organic anion transporting polypeptide 1B3 (Ct-OATP1B3) has been identified as a cancer-specific transcript in various solid cancers, including colorectal cancer. Given its excellent cancer-specific expression profile, we hypothesized that Ct-OATP1B3 could represent a promising target for cancer-specific expression of the suicide gene, herpes simplex virus 1 thymidine kinase (HSV-tk), via a spliceosome-mediated RNA trans-splicing (SMaRT) approach. SMaRT technology is used to recombine two RNA molecules to generate a chimeric transcript. In this study, we engineered an RNA trans-splicing molecule carrying a translation-defective HSV-tk sequence (RTM44), which was capable of inducing its own trans-splicing to the desired Ct-OATP1B3 pre-mRNA target. RTM44 expression in LS180 cells resulted in generation of Ct-OATP1B3/HSV-tk fusion mRNA. A functional translation start site contributed by the target pre-mRNA restored HSV-tk protein expression, rendering LS180 cells sensitive to ganciclovir treatment in vitro and in xenografted mice. The observed effects are ascribed to accurate and efficient trans-splicing, as they were absent in cells carrying a splicing-deficient mutant of RTM44. Collectively, our data highlights Ct-OATP1B3 as an ideal target for the HSV-tk SMaRT suicide system, which opens up new translational avenues for Ct-OATP1B3-targeted cancer therapy.

Cancer-type OATP1B3 mRNA has the potential to become a detection and prognostic biomarker for human colorectal cancer.

AIM: We aimed to clarify diagnostic and prognostic biomarker potentials of cancer-type organic anion transporting polypeptide 1B3 (Ct-OATP1B3) mRNA in colorectal cancer (CRC) patients. PATIENTS & METHODS: Ct-OATP1B3 mRNA levels in 97 CRC and adjacent normal colon tissues were measured by real-time PCR. The receiver operating characteristic curve analysis and the Kaplan-Meier curve analysis were performed to characterize its biomarker potentials. RESULTS: Ct-OATP1B3 mRNA showed noticeable diagnostic power (the area under the receiver operating characteristic = 0.91) in the CRC patients. Additionally, the higher/lower mRNA expression was clearly associated with better/poorer overall survival in the CRC patients (p < 0.05). CONCLUSION: Ct-OATP1B3 mRNA has the potential to be a tissue-based biomarker for definitive diagnosis and prognostic stratification in CRC.

Unique expression features of cancer-type organic anion transporting polypeptide 1B3 mRNA expression in human colon and lung cancers.

BACKGROUND: We have previously identified the cancer-type organic anion transporting polypeptide 1B3 (Ct-OATP1B3) mRNA in several human colon and lung cancer tissues. Ct-OATP1B3 is a variant of the liver-type OATP1B3 (Lt-OATP1B3) mRNA, which is a hepatocyte plasma membrane transporter with broad substrate specificity. However, in cancer tissues, both the detailed characteristics of Ct-OATP1B3 mRNA expression and its biological functions remain unclear. With this point in mind, we sought to characterize Ct-OATP1B3 mRNA expression in colon and lung cancer tissues. In addition, we attempted to obtain functional implication of Ct-OATP1B3 in cancer cells. METHODS: Matched pairs of cancer and normal tissues were collected from 39 colon cancer and 28 lung cancer patients. The OATP1B3 mRNA expression levels in each of these tissues were separately determined by quantitative real-time polymerase chain reaction. Mann-Whitney U test and Fisher's exact test were used in statistical analysis. The Ct-OATP1B3 functional expression in colon cancer cells was then examined by Western blotting and transport analyses. RESULTS: Ct-OATP1B3 mRNA, but not Lt-OATP1B3 mRNA, was abundantly expressed in colon cancer tissues at a higher detection frequency (87.2%) than that of the adjacent normal tissues (2.6%). Furthermore, it was found that Ct-OATP1B3 mRNA expression was often detected in early colon cancer stages (88.9%, n = 18), and that its expression was associated with well-differentiated colon cancer statuses. On the other hand, Ct-OATP1B3 mRNA also showed a predominant and cancer-associated expression profile in lung tissues, although at frequencies and expression levels that were lower than those obtained from colon cancer. As for attempts to clarify the Ct-OATP1B3 functions, neither protein expression nor transport activity could be observed in any of the cell lines examined. CONCLUSIONS: Based on the unique characteristics of the Ct-OATP1B3 mRNA expression profile identified in this study, Ct-OATP1B3 mRNA can be expected to become a biomarker candidate for use in colon (and lung) cancer diagnosis. Simultaneously, our results advance the possibility that Ct-OATP1B3 might play yet unidentified roles, in addition to transporter function, in cancer cell biology.