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Introduction: Atezolizumab and bevacizumab (AB) therapy was the first-line treatment for unresectable hepatocellular carcinoma (u-HCC). However, the predictive marker of therapeutic response that can be easily used in clinical practice is still unknown. We prospectively investigated the utility of time-intensity curve (TIC) analysis using contrast-enhanced ultrasound (CEUS) as a predictive indicator of therapeutic response after the start of AB therapy. Methods: Thirty-five patients who received AB therapy for u-HCC were included in this study. TIC analysis was performed in 28 patients who were able to undergo CEUS before and 3–7 days after administration. We analyzed prognostic factors related to the initial therapeutic response and long progression-free survival (PFS). Results: The initial therapeutic response using dynamic computed tomography or Gd-EOB magnetic resonance imaging at 8–12 weeks after administration was partial response/stable disease/progressive disease (PD) in 14/12/9 cases (40/34/26%). Cases with PD (n = 9) had more cases without decreased blood flow in TIC analysis compared with cases with non-PD (100 vs. 18%, p = 0.001). Cases without decreased blood flow in TIC analysis (n = 10) had more cases with PD compared with cases with decreased blood flow (60 vs. 0%, p = 0.001). PFS in patients without decreased blood flow early after the administration was shorter than that in those with decreased blood flow (9.1 vs. 28 weeks, p = 0.0051). Conclusion: Early evaluation by TIC analysis using CEUS may be useful in predicting the therapeutic response in patients treated with AB therapy for u-HCC.

Recently, with the advent of sofosbuvir/velpatasvir therapy, sustained virological response (SVR) can now be achieved even in patients with decompensated cirrhosis (dLC). However, the prognosis after SVR does not always improve in dLC, and appropriate indicators enabling prediction of prognosis is desired.Serum IP-10/CXCL10 levels were measured in 47 patients (15 chronic hepatitis [CH], 17 compensated cirrhosis [cLC], and 15 dLC) receiving direct acting antiviral (DAA) therapy, and their changes during the therapy were examined.All the patients achieved SVR. In patients with CH, the average IP-10 level was 367, 102, and 68 pg/ml respectively at baseline, at the end of therapy and at 12 weeks after SVR (SVR12), and was decreased upon DAA therapy (P 0.001). In patients with cLC, IP-10 was respectively 215, 91, and 77 pg/ml, and was decreased upon DAA therapy (P 0.001) while it was 283, 131, and 182 pg/ml in patients with dLC and there was no evident decrease (P = 0.55). When patients with dLC were further classified depending on the difference in Child-Pugh (CP) score improvement at SVR12, a significant decrease in IP-10 was observed after treatment in those with improvement (P = 0.023) while a significant increase was observed in those without improvement (P = 0.016).While serum IP-10 level was decreased in patients with CH/cLC and dLC with post-SVR-CP improvement following SVR, it was increased in patients with dLC without post-SVR CP improvement. The result indicates that IP-10 dynamics may be useful for predicting liver function after DAA therapy.

The method of analyzing individual resistant hepatitis C virus (HCV) by a combination of haplotyping and resistance-associated substitution (RAS) has not been fully elucidated because conventional sequencing has only yielded short and fragmented viral genomes. We performed haplotype analysis of HCV mutations in 12 asunaprevir/daclatasvir treatment-failure cases using the Oxford Nanopore sequencer. This enabled single-molecule long-read sequencing using rolling circle amplification (RCA) for correction of the sequencing error. RCA of the circularized reverse-transcription polymerase chain reaction products successfully produced DNA longer than 30 kilobase pairs (kb) containing multiple tandem repeats of a target 3 kb HCV genome. The long-read sequencing of these RCA products could determine the original sequence of the target single molecule as the consensus nucleotide sequence of the tandem repeats and revealed the presence of multiple viral haplotypes with the combination of various mutations in each host. In addition to already known signature RASs, such as NS3-D168 and NS5A-L31/Y93, there were various RASs specific to a different haplotype after treatment failure. The distribution of viral haplotype changed over time; some haplotypes disappeared without acquiring resistant mutations, and other haplotypes, which were not observed before treatment, appeared after treatment. Conclusion: The combination of various mutations other than the known signature RAS was suggested to influence the kinetics of individual HCV quasispecies in the direct-acting antiviral treatment. HCV haplotype dynamic analysis will provide novel information on the role of HCV diversity within the host, which will be useful for elucidating the pathological mechanism of HCV-related diseases.

The damping ratio (DR) and the loss modulus (G″) obtained by 3D MR elastography complex modulus analysis has been reported recently to reflect early intrahepatic inflammation, and is expected to be a noninvasive biomarker of inflammation in nonalcoholic fatty liver disease (NAFLD). However, the role of the DR and the G″ in Japanese NAFLD patients remains unclear.We enrolled 39 Japanese patients with NAFLD who underwent liver biopsy and 3D MR elastography within 1 month and analyzed the association between DR, G″, and histological activity.Regarding DR, no evident correlation was observed between the DR and histological activity (p = 0.14) when patients with all fibrosis stages were included. However, when patients were restricted up to stage F2 fibrosis, the association of the DR and inflammation became significant, the DR increasing with the degree of activity (p = 0.02). Among the constituents of fibrosis activity, ballooning correlated with the DR (p 0.01) while lobular inflammation did not. Regarding G″, it was correlated with histological activity (p 0.01), ballooning (p 0.01), and lobular inflammation (p 0.01) in patients with all fibrosis stages and in patients up to F2 fibrosis (p = 0.03 for activity and p = 0.04 for ballooning). The best cutoff value of DR for hepatitis activity in patients within the F2 stage was 0.094 (area under the receiver operating characteristic curve 0.775, 95% CI: 0.529-1.000) and G″ was 0.402 (area under the receiver operating characteristic curve 0.825, 95% CI: 0.628-1.000).The DR and G″ reflected the histological activity in Japanese patients with NAFLD during the early stage, indicating these values for noninvasive diagnosis of inflammation in Japanese patients with NAFLD.

AIM Recently, serum hepatitis B virus (HBV)-RNA has been reported to be detectable even when HBV particle production is inhibited by nucleot(s)ide analogues (NAs). However, the dynamics of the HBV-RNA sequence compared with those of HBV-DNA during the emergence of antiviral resistance are yet to be elucidated. METHODS First, we quantified serum HBV-RNA in 181 infected patients, and its relationships with clinical characteristics as well as HBV markers were investigated. Next, we undertook simultaneous deep sequencing of HBV-RNA/HBV-DNA and their dynamics among four patients receiving NA therapy who were experiencing viral breakthrough. RESULTS Serum HBV-RNA was detected in 25% (31/123) of cases among patients with HBV without NAs, and the detection rate was significantly high in hepatitis B e antigen-positive cases with high viral activity. In patients with chronic hepatitis, hepatitis B core-related antigen was significantly correlated with serum HBV-RNA irrespective of NA use. In the analysis of the four patients experiencing viral breakthrough, no NA resistance mutation was detected in the serum HBV-RNA immediately before the breakthrough. However, NA-resistant sequences appeared at the rates of 0%, 3%, 14%, and 100%, and the NA-resistant HBV-RNA sequence rate was correlated with the peak HBV-DNA titer multiplied by the HBV-DNA detection duration during the breakthrough (R2 = 0.978) observed before redisappearance of HBV-DNA following the addition of new NA. CONCLUSION Serum HBV-RNA could reflect the transcriptional activity of covalently closed circular DNA and hepatitis B core-related antigen. The dynamics of HBV-RNA could help understanding of the turnover process of HBV covalently closed circular DNA in the liver.

Liver damage presented as alanine aminotransferase (ALT) elevation and high ALT-caused treatment discontinuation occurs with high frequency in Japanese patients receiving daclatasvir plus asunaprevir (DCV/ASV) therapy for hepatitis C virus (HCV) infection, and its mechanism is unknown. A total of 247 Japanese patients consisting of two independent cohorts with genotype-1b HCV infection receiving DCV/ASV therapy were included. The association of ALT levels during therapy and single nucleotide polymorphisms (SNP) of five drug-metabolizing enzyme loci selected for their possible influence on NS3/4A and NS5A inhibitors was investigated. Among five SNPs, we found a significant correlation between the presence of the UGT1A1 rs4148323 A allele and ALT elevation (Grade 3 elevation in AA 57%, AG 18%, and GG 4%, P = 8.4E − 06) and drug discontinuation (AA 22%, AG 11%, and GG 2.5%, P = 8.7E − 04), while no association was observed with ALT values at baseline (Grade 3 elevation AA 0%, AG 4%, and GG 2%, P = 0.5). In contrast, patients with risk A allele for drug-induced ALT elevation had a tendency to respond more favorably to treatment (AA 100%, AG 93%, and GG 90%, P = 0.29). Through the analysis we suggest that the A allele in UGT1A1 rs4148323 (UGT1A1*6), which is highly prevalent in the Japanese population, should be considered a risk for the development of DCV/ASV therapy-induced ALT elevation. Pretreatment SNP testing of UGT1A1*6 might be beneficial for the prediction of liver damage induced by DCV/ASV or even by DCV/ASV plus beclabuvir.

AIM The landscape of cancer-related genetic aberrations in hepatocellular carcinoma (HCC) has gradually become clear through recent next-generation sequencing studies. However, it remains unclear how genetic aberrations correlate with imaging and histological findings. METHODS Using 117 formalin-fixed paraffin-embedded specimens of primary liver tumors, we undertook targeted next-generation sequencing of 50 cancer-related genes and digital polymerase chain reaction of hTERT. After classifying tumors into several imaging groups by hierarchal clustering with the information from gadoxetic acid enhanced magnetic resonance imaging, contrast-enhanced computed tomography, contrast-enhanced ultrasound, and diffusion-weighted imaging magnetic resonance imaging, the correlation between genetic aberrations and imaging and histology were investigated. RESULTS Most frequent mutations were hTERT (61.5%), followed by TP53 (42.7%), RB1 (24.8%), and CTNNB1 (18.8%). Liver tumors were classified into six imaging groups/grades, and the prevalence of hTERT mutations tended to increase with the advancement of imaging/histological grades (P = 0.026 and 0.13, respectively), whereas no such tendency was evident for TP53 mutation (P = 0.78 and 1.00, respectively). Focusing on the mutations in each tumor, although the variant frequency (VF) of hTERT did not change (P = 0.36 and 0.14, respectively) in association with imaging/histological grades, TP53 VF increased significantly (P = 0.004 and

Radiofrequency ablation (RFA) is considered the most effective treatment for early‐stage hepatocellular carcinoma (HCC) patients unsuitable for resection. However, poor outcome after RFA has occasionally been reported worldwide. To predict such an outcome, we investigated imaging findings using contrast‐enhanced ultrasonography (CEUS) with Sonazoid and serum tumor markers before RFA. This study included 176 early‐stage HCC patients who had initially achieved successful RFA. Patients were examined using CEUS; their levels of alpha‐fetoprotein (AFP), Lens culinaris agglutinin‐reactive fraction of AFP (AFP‐L3), and des‐gamma‐carboxy prothrombin before RFA were measured. Sonazoid provided parenchyma‐specific contrast imaging and facilitated tumor vascular architecture imaging through maximum intensity projection (MIP). Kaplan–Meier analysis examined cumulative rates of local tumor progression, intrasubsegmental recurrence, and survival; factors associated with these were determined with Cox proportional hazards analysis. Local tumor progression (n = 15), intrasubsegmental recurrence (n = 46), and death (n = 18) were observed. Irregular pattern in MIP classification and serum AFP‐L3 level (>10%) before RFA were identified as independent risk factors for local tumor progression and intrasubsegmental recurrence. These two factors were independently associated with poor survival after RFA (irregular pattern in MIP: hazard ratio, (HR) = 8.26; 95% confidence interval, (CI) = 2.24–30.3; P = 0.002 and AFP‐L3 > 10%: HR = 2.94; 95% CI = 1.09–7.94; P = 0.033). Irregular MIP pattern by CEUS and high level of serum AFP‐L3 were independent risk factors for poor outcome after successful RFA. The Patients with these findings should be considered as special high‐risk group in early‐stage HCC.

AIM Although the viral markers hepatitis B surface antigen (HBsAg) and hepatitis B core-related antigen (HbcrAg) could reflect intrahepatic hepatitis B virus (HBV) replication activity and constitute important biomarkers for hepatocellular carcinoma (HCC), the value of using these two markers in combination for assessing HCC risk has not been clarified in detail. METHODS Four hundred and forty-nine consecutive patients with chronic HBV infection were included in the study and the association of HBsAg and HBcrAg with HCC risk was investigated cross-sectionally, as well as longitudinally. RESULTS When the high value cut-offs of HBsAg and HBcrAg were defined as 3.0 log IU/mL and 3.0 log U/mL, respectively, patients with a history of HCC were found frequently in the low HBsAg group (P = 0.002) and high HBcrAg group (P

Aim The presence of resistance-associated variants (RAV) may attenuate the efficacy of direct-acting antivirals (DAA) in combination therapy for hepatitis C. The aim of this study was to characterize the NS3 and NS5A regions of hepatitis C virus (HCV) in naturally occurring RAV. Methods The NS3 and NS5A regions of HCV were amplified by nested polymerase chain reaction and their nucleotide sequences were determined by direct sequencing in 493 genotype 1b patients naive to DAA-based therapies. The effect of baseline RAV on response to pegylated interferon and ribavirin therapy was analyzed in 65 patients after stratification by interleukin (IL)-28B genotype. Results The incidence of RAV was 7.9% in NS3 (V36I/L, 1.2%; T54S, 2.8%; Q80K/R, 3.0%; A156S, 0.2%; and D168E/T, 2.4%) and 20.2% in NS5A (L31I/M, 2.2%; and Y93H, 19.0%). The incidence in interferon experienced and naive patients was similar. The incidence of Y93H in NS5A was significantly higher in the IL-28B TT genotype (rs8099917) than non-TT (27.1% vs 9.5%, P

We performed a prospective study to evaluate the ability of L-carnitine, which is involved in the β-oxidation of fatty acids, to reduce muscle cramps in patients with cirrhosis. Consecutive patients with cirrhosis and muscle cramps were given L-carnitine 300 mg, 3 times/day (900 mg/day, n = 19) or 4 times/day (1200 mg/day, n = 23) for 8 weeks. The frequency of muscle cramps was assessed by questionnaires, and the degree of muscle cramping was assessed by using the visual analogue scale (VAS). Muscle cramping was reduced in 88.1% of all subjects at the end of the 8-week study period and disappeared for 28.6% of patients. Overall VAS scores decreased significantly from 69.9 ± 22.5 at baseline to 26.2 ± 29.1 after 8 weeks (P .0001). The dose of L-carnitine was significantly associated with percentages of patients with reduced muscle cramps after 8 weeks (43.5% in the 1200 mg/day group vs 10.5% in the 900 mg/day group, P = .037) and VAS scores at 8 weeks (9.9 ± 13.5 in the 1200 mg/day group vs 39.6 ± 31.9 in the 900 mg/day group, P = .003). No adverse events were reported. Therefore, L-carnitine appears to be safe and effective for reducing liver cramps in patients with cirrhosis.

Aims Wisteria floribunda agglutinin (WFA)-positive human Mac-2-binding protein (WFA+-M2BP) is a new glycol marker related to liver fibrosis. The aim of the present study was to evaluate WFA+-M2BP as a predictor of hepatocellular carcinoma (HCC) development in patients with chronic hepatitis C. Methods This case–control study included 14 patients with chronic hepatitis C who developed HCC and 52controls, matched for age, gender, and fibrosis stage. WFA+-M2BP was measured at biopsy and follow-up. Time zero was set at the date of liver biopsy. Results WFA+-M2BP increased stepwise with progression of liver fibrosis (p < 0.001). Cumulative incidence of HCC development was significantly higher in patients with WFA+-M2BP ≥4.2 (p < 0.001) or in those with time-course changes in WFA+-M2BP (ΔWFA+-M2BP/year) ≥0.3 (p = 0.03). Multivariate analyses demonstrated that WFA+-M2BP ≥4.2 [hazard ratio (HR): 4.1, 95% confidence interval (CI): 1.1–15, p = 0.04], ΔWFA+-M2BP/year ≥0.3 (HR: 5.5, 95% CI: 1.5–19, p = 0.008), and AFP ≥10 ng/ml (HR: 4.7, 95% CI: 1.1–19, p = 0.03) were independent predictive factors of HCC development. Based on these data, we developed a simple scoring system to predict HCC development using these three factors. Using these scores, patients were classified into four groups; cumulative incidence of HCC development significantly increased with increasing scores (p < 0.001). Conclusions WFA+-M2BP measurements and time-course changes in WFA+-M2BP can be used to identify patients at high risk of HCC development. Real-time monitoring of WFA+-M2BP can be a novel predictor of HCC development.

Objectives: This study aimed to build a prediction score of prognosis for patients with advanced hepatocellular carcinoma (HCC) after sorafenib treatment. Methods: A total of 165 patients with advanced HCC who were treated with sorafenib were analyzed. Readily available baseline factors were used to establish a scoring system for the prediction of survival. Results: The median survival time (MST) was 14.2 months. The independent prognostic factors were C-reactive protein (CRP) 3.5 g/dL (HR =0.55), alpha-fetoprotein Conclusions: A novel prognostic scoring system, which includes the CRP level, has the ability to stratify the prognosis of patients with advanced stage HCC after treatment with sorafenib.

The water channel aquaporin 2 (AQP2) at the apical membrane of renal collecting duct cells mediates water reabsorption. The expression of AQP2 at the apical membrane is tightly regulated by vasopressin and was quantitated by measurement of the urinary form by a recently developed ELISA. Tolvaptan, an antagonist of vasopressin type 2 receptor, inhibits water reabsorption in cirrhosis. The aim of this study was to determine the correlation between the pharmacological effect of tolvaptan and the dynamics of urinary AQP2 levels. Tolvaptan was administered to 41 cirrhotic patients with ascites unresponsive to standard diuretic therapy. Urinary excretion of AQP2 and urinary osmolarity were measured at the baseline and at 4, 8, and 24 h after administration of tolvaptan. At the baseline, urinary AQP2/creatinine ratios were significantly higher in cirrhotic patients with ascites than in healthy controls (P

The presence of resistance-associated variants (RAV) may attenuate the efficacy of direct-acting antivirals (DAA) in combination therapy for hepatitis C. The aim of this study was to characterize the NS3 and NS5A regions of hepatitis C virus (HCV) in naturally occurring RAV.The NS3 and NS5A regions of HCV were amplified by nested polymerase chain reaction and their nucleotide sequences were determined by direct sequencing in 493 genotype 1b patients naive to DAA-based therapies. The effect of baseline RAV on response to pegylated interferon and ribavirin therapy was analyzed in 65 patients after stratification by interleukin (IL)-28B genotype.The incidence of RAV was 7.9% in NS3 (V36I/L, 1.2%; T54S, 2.8%; Q80K/R, 3.0%; A156S, 0.2%; and D168E/T, 2.4%) and 20.2% in NS5A (L31I/M, 2.2%; and Y93H, 19.0%). The incidence in interferon experienced and naive patients was similar. The incidence of Y93H in NS5A was significantly higher in the IL-28B TT genotype (rs8099917) than non-TT (27.1% vs 9.5%, P 0.001). The virological response to pegylated interferon plus ribavirin therapy was not affected by the presence of RAV in IL-28B TT genotype.RAV, especially Y93H in the NS5A region, were highly prevalent in DAA naive patients with genotype 1b HCV in Japan and were linked to IL-28B TT genotype. Interferon-based therapy could be an alternative for patients with RAV because these variants did not attenuate the response to that therapy. The analysis of RAV may impact the selection of the optimal treatment strategy.

Wisteria floribunda agglutinin (WFA)-positive human Mac-2-binding protein (WFA(+) -M2BP) is a new glycol marker related to liver fibrosis. The aim of the present study was to evaluate WFA(+) -M2BP as a predictor of hepatocellular carcinoma (HCC) development in patients with chronic hepatitis C.This case-control study included 14 patients with chronic hepatitis C who developed HCC and 52controls, matched for age, gender, and fibrosis stage. WFA(+) -M2BP was measured at biopsy and follow-up. Time zero was set at the date of liver biopsy.WFA(+) -M2BP increased stepwise with progression of liver fibrosis (p0.001). Cumulative incidence of HCC development was significantly higher in patients with WFA(+) -M2BP ≥4.2 (p0.001) or in those with time-course changes in WFA(+) -M2BP (ΔWFA(+) -M2BP/year) ≥0.3 (p = 0.03). Multivariate analyses demonstrated that WFA(+) -M2BP ≥4.2 [hazard ratio (HR): 4.1, 95% confidence interval (CI): 1.1-15, p = 0.04], ΔWFA(+) -M2BP/year ≥0.3 (HR: 5.5, 95% CI: 1.5-19, p = 0.008), and AFP ≥10 ng/ml (HR: 4.7, 95% CI: 1.1-19, p = 0.03) were independent predictive factors of HCC development. Based on these data, we developed a simple scoring system to predict HCC development using these three factors. Using these scores, patients were classified into four groups; cumulative incidence of HCC development significantly increased with increasing scores (p0.001).WFA(+) -M2BP measurements and time-course changes in WFA(+) -M2BP can be used to identify patients at high risk of HCC development. Real-time monitoring of WFA(+) -M2BP can be a novel predictor of HCC development.

The fibrosis stage, which is evaluated by the distribution pattern of collagen fibers, is a major predictor for the development of hepatocellular carcinoma (HCC) for patients with hepatitis C. Meanwhile, the role of elastin fibers has not yet been elucidated. The present study was conducted to determine the significance of quantifying both collagen and elastin fibers.We enrolled 189 consecutive patients with hepatitis C and advanced fibrosis. Using Elastica van Gieson-stained whole-slide images of pretreatment liver biopsies, collagen and elastin fibers were evaluated pixel by pixel (0.46 μm/pixel) using an automated computational method. Consequently, fiber amount and cumulative incidences of HCC within 3 years were analyzed.There was a significant correlation between collagen and elastin fibers, whereas variation in elastin fiber was greater than in collagen fiber. Both collagen fiber (p = 0.008) and elastin fiber (p0.001) were significantly correlated with F stage. In total, 30 patients developed HCC during follow-up. Patients who have higher elastin fiber (p = 0.002) in addition to higher collagen fiber (p = 0.05) showed significantly higher incidences of HCC. With regard to elastin fiber, this difference remained significant in F3 patients. Furthermore, for patients with a higher collagen fiber amount, higher elastin was a significant predictor for HCC development (p = 0.02).Computational analysis is a novel technique for quantification of fibers with the added value of conventional staging. Elastin fiber is a predictor for the development of HCC independently of collagen fiber and F stage.

Background & Aims The presence of resistance-associated variants (RAVs) of hepatitis C virus (HCV) attenuates the efficacy of direct acting antivirals (DAAs). The objective of this study was to characterize the susceptibility of RAVs to interferon-based therapy. Methods Direct and deep sequencing were performed to detect Y93H RAV in the NS5A region. Twenty nine genotype 1b patients with detectable RAV at baseline were treated by a combination of simeprevir, pegylated interferon and ribavirin. The longitudinal changes in the proportion of Y93H RAV during therapy and at breakthrough or relapse were determined. Results By direct sequencing, Y93H RAV became undetectable or decreased in proportion at an early time point during therapy (within 7 days) in 57% of patients with both the Y93H variant and wild type virus at baseline when HCV RNA was still detectable. By deep sequencing, the proportion of Y93H RAV against Y93 wild type was 52.7% (5.8%– 97.4%) at baseline which significantly decreased to 29.7% (0.16%- 98.3%) within 7 days of initiation of treatment (p = 0.023). The proportion of Y93H RAV was reduced in 21 of 29 cases (72.4%) and a marked reduction of more than 10% was observed in 14 cases (48.7%). HCV RNA reduction was significantly greater for Y93H RAV (-3.65±1.3 logIU/mL/day) than the Y93 wild type (-3.35±1.0 logIU/mL/day) (p

The human and Old World primate genomes possess conserved endogenous retrovirus sequences that have been implicated in evolution, reproduction, and carcinogenesis. Human endogenous retrovirus (HERV)-K with 5′LTR-gag-pro-pol-env-rec/np9-3′LTR sequences represents the newest retrovirus family that integrated into the human genome 1 to 5 million years ago. Although a high-level expression of HERV-K in melanomas, breast cancers, and terato-carcinomas has been demonstrated, the mechanism of the lineage-specific activation of the long terminal repeat (LTR) remains obscure. We studied chromosomal HERV-K expression in MeWo melanoma cells in comparison with the basal expression in human embryonic kidney 293 (HEK293) cells. Cloned LTR of HERV-K (HML-2.HOM) was also characterized by mutation and transactivation experiments. We detected multiple transcriptional initiator (Inr) sites in the LTR by rapid amplification of complementary DNA ends (5′ RACE). HEK293 and MeWo showed different Inr usage. The most potent Inr was associated with a TATA box and three binding motifs of microphthalmia-associated transcription factor (MITF). Both chromosomal HERV-K expression and the cloned LTR function were strongly activated in HEK293 by transfection with MITF-M, a melanocyte/melanoma–specific isoform of MITF. Coexpression of MITF and the HERV-K core antigen was detected in retinal pigmented epithelium by an immunofluorescence analysis. Although malignant melanoma lines MeWo, G361, and SK-MEL-28 showed enhanced HERV-K transcription compared with normal melanocytes, the level of MITF-M messenger RNA persisted from normal to transformed melanocytes. Thus, MITF-M may be a prerequisite for the pigmented cell lineage–specific function of HERV-K LTR, leading to the high-level expression in malignant melanomas.