Sunghyun Henry Kim

Prediction of Recurrence-Free Survival in Postoperative Non–Small Cell Lung Cancer Patients by Using an Integrated Model of Clinical Information and Gene Expression

Purpose: One of the main challenges of lung cancer research is identifying patients at high risk for recurrence after surgical resection. Simple, accurate, and reproducible methods of evaluating individual risks of recurrence are needed. Experimental Design: Based on a combined analysis of time-to-recurrence data, censoring information, and microarray data from a set of 138 patients, we selected statistically significant genes thought to be predictive of disease recurrence. The number of genes was further reduced by eliminating those whose expression levels were not reproducible by real-time quantitative PCR. Within these variables, a recurrence prediction model was constructed using Cox proportional hazard regression and validated via two independent cohorts (n = 56 and n = 59). Results: After performing a log-rank test of the microarray data and successively selecting genes based on real-time quantitative PCR analysis, the most significant 18 genes had P values of <0.05. After subsequent stepwise variable selection based on gene expression information and clinical variables, the recurrence prediction model consisted of six genes (CALB1, MMP7, SLC1A7, GSTA1, CCL19, and IFI44). Two pathologic variables, pStage and cellular differentiation, were developed. Validation by two independent cohorts confirmed that the proposed model is significantly accurate (P = 0.0314 and 0.0305, respectively). The predicted median recurrence-free survival times for each patient correlated well with the actual data. Conclusions: We have developed an accurate, technically simple, and reproducible method for predicting individual recurrence risks. This model would potentially be useful in developing customized strategies for managing lung cancer.

The saving-investment correlation puzzle is still a puzzle

Abstract A number of simulation studies claim to have solved the Feldstein–Horioka puzzle by demonstrating that a high time-series correlation between saving and investment naturally arises from business cycle shocks. This paper uses panel data of saving and investment controlled for business cycle shocks to empirically test the significance of cyclical shocks — productivity, fiscal and the terms of trade shocks — in explaining a high saving–investment correlation. The estimation results reveal that conventional aggregate shocks only partially explain the high saving–investment correlation. Moreover, country differences in the size of the GNP and the non-traded sector do not significantly affect the saving–investment correlation. The saving–investment correlation puzzle remains a puzzle after all.

Adjuvant chemoradiation versus chemotherapy in completely resected advanced gastric cancer with D2 nodal dissection

Aim:  Adjuvant chemoradiation has become a standard of care in the USA. We evaluated the efficacy and toxicity of adjuvant chemoradiation versus chemotherapy in completely resected locally advanced gastric cancer.

DYNAMICS OF OPEN-ECONOMY BUSINESS-CYCLE MODELS: ROLE OF THE DISCOUNT FACTOR

This paper examines the dynamic implications of different preference formulations in open-economy business-cycle models with incomplete asset markets. In particular, we study two preference formulations: a time-separable preference formulation with a fixed discount factor, and a time-nonseparable preference structure with an endogenous discount factor. We analyze the moment implications of two versions of an otherwise identical open-economy model—one with a fixed discount factor and the other with an endogenous discount factor—and study impulse responses to productivity and world real-interest-rate shocks. Our results suggest that business-cycle implications of the two models are quite similar under conventional parameter values. We also find that the approximation errors associated with the solutions of these two models are of the same magnitude.

Patience, persistence, and welfare costs of incomplete markets in open economies

In this paper, we investigate the welfare implications of alternative financial market structures in a two-country endowment economy model. In particular, we obtain an analytic expression for the expected lifetime utility of the representative household when sovereign bonds are the only internationally traded asset, and we compare this welfare level with that obtained under complete asset markets. The welfare cost of incomplete markets is negligible if agents are very patient and shocks are not very persistent, but this cost is dramatically larger if agents are relatively impatient and shocks are highly persistent. For realistic cases in which agents are very patient and shocks are highly persistent (that is, the discount factor and the first-order autocorrelation are both near unity), the welfare cost of incomplete markets is highly sensitive to the specific values of these parameters. Finally, using a non-linear solution algorithm, we confirm that a two-country production economy with endogenous labor supply has qualitatively similar welfare properties.

Erythroid Cell-Specific α-Globin Gene Regulation by the CP2 Transcription Factor Family

ABSTRACT We previously demonstrated that ubiquitously expressed CP2c exerts potent erythroid-specific transactivation of α-globin through an unknown mechanism. This mechanism is reported here to involve specific CP2 splice variants and protein inhibitor of activated STAT1 (PIAS1). We identify a novel murine splice isoform of CP2, CP2b, which is identical to CP2a except that it has an additional 36 amino acids encoded by an extra exon. CP2b has an erythroid cell-specific transcriptional activation domain, which requires the extra exon and can form heteromeric complexes with other CP2 isoforms, but lacks the DNA binding activity found in CP2a and CP2c. Transcriptional activation of α-globin occurred following dimerization between CP2b and CP2c in erythroid K562 and MEL cells, but this dimerization did not activate the α-globin promoter in nonerythroid 293T cells, indicating that an additional erythroid factor is missing in 293T cells. PIAS1 was confirmed as a CP2 binding protein by the yeast two-hybrid screen, and expression of CP2b, CP2c, and PIAS1 in 293T cell induced α-globin promoter activation. These results show that ubiquitously expressed CP2b exerts potent erythroid cell-specific α-globin gene expression by complexing with CP2c and PIAS1.

Regional Versus Global Risk Sharing in East Asia

This paper estimates the degree of risk sharing for each of 10 East Asian countries with countries in the region and with OECD countries by using cross-country consumption correlations and formal regression analysis. Risk sharing is found to be far from complete and quite low for most of the countries. Taiwan and Singapore have the highest risk sharing. Indonesia and Malaysia have the lowest (and significantly negative) risk sharing. The degree of risk sharing does not increase in most countries over 19702000. For the less-developed countries, potential gains from risk sharing would be larger with OECD countries than with East Asian countries.

Dynamics of Open Economy Business Cycle Models: Understanding the Role of the Discount Factor

This paper examines the dynamic implications of different preference formulations in open economy business cycle models with incomplete asset markets. In particular, we study two preference formulations: a time separable preference formulation with a fixed discount factor, and a time non-separable preference structure with an endogenous discount factor. We analyze the moment implications of two versions of an otherwise identical open economy model -- one with a fixed discount factor and the other with an endogenous discount factor -- and study impulse responses to productivity and world real interest rate shocks. Our results suggest that business cycle implications of the two models are quite similar under conventional parameter values. We also find the approximation errors associated with the solutions of these two models are of the same magnitude.

Pathological correlation with diffusion restriction on diffusion-weighted imaging in patients with pathological complete response after neoadjuvant chemoradiation therapy for locally advanced rectal cancer: preliminary results

OBJECTIVE The objective of this study was to assess causative pathological factors associated with diffusion restriction on diffusion-weighted imaging (DWI) in patients who achieved pathological complete response (pCR) after treatment with neoadjuvant chemoradiation therapy (CRT) for locally advanced rectal cancer. METHODS In total, 43 patients with locally advanced rectal cancer (≥T3 or lymph node positive) who underwent neoadjuvant CRT, subsequent surgery and ultimately achieved pCR were enrolled. All patients underwent pre- and post-CRT 3.0 T rectal MRI with DWI. Two radiologists blinded to pathological staging reviewed pre- and post-CRT 3.0 T rectal MRI for the presence of diffusion restriction in the corresponding tumour areas on post-CRT DWI, with a third radiologist arbitrating any disagreement. The consensus of these findings was then correlated with pathological data such as intramural mucin and the degree of proctitis and mural fibrosis seen on surgical specimen. Additionally, the pre-CRT tumour volume was measured to define the effect of this variable on the degree of radiation proctitis and fibrosis, as well as the presence of intramural mucin. RESULTS Diffusion restriction occurred in 18 subjects (41.9%), while 25 subjects remained diffusion restriction-free (58.1%). The diffusion restriction group tended to have more severe proctitis and mural fibrosis when compared with non-diffusion restriction group (p<0.001). Intramural mucin was also more common in the diffusion restriction group (p=0.052). Higher pre-CRT tumour volumes were significantly predictive of the degree of proctitis (p=0.0247) and fibrosis (p=0.0445), but not the presence of intramural mucin (p=0.0944). Proctitis and mural fibrosis severity were also identified as independent pathological risk factors for diffusion restriction on multivariate analysis (p=0.0073 and 0.0011, respectively). CONCLUSION Both radiation-induced proctitis and fibrosis were significant and independent predictors of diffusion restriction in patients achieving pCR after treatment with neoadjuvant CRT for locally advanced rectal cancer, and pre-CRT tumour volume significantly affects both variables.

Fear of Floating in East Asia

We examine the de facto exchange rate arrangements in East Asia by applying the methods suggested by Calvo and Reinhart (2002) and Kim (2004). Estimation results suggest that three East Asian countries in our sample adopted a hard peg or a peg with capital account restrictions in the post-crisis period. Five East Asian countries in our sample moved toward a more flexible exchange rate arrangement in the post-crisis period. At least three of these five countries (Korea, Indonesia and Thailand) achieved the level of exchange rate flexibility that is close to the level accomplished in the free floater such as Australia. These results suggest that “Fear of Floating” of East Asian countries is not prevalent in the post-crisis period and that the bi-polar view has some support in East Asian samples.