Potent obatoclax cytotoxicity and activation of triple death mode killing across infant acute lymphoblastic leukemia.

Survival in infants younger than 1 year who have acute lymphoblastic leukemia (ALL) is inferior whether MLL is rearranged (R) or germline (G). MLL translocations confer chemotherapy resistance, and infants experience excess complications. We characterized in vitro sensitivity to the pan-antiapoptotic BCL-2 family inhibitor obatoclax mesylate in diagnostic leukemia cells from 54 infants with ALL/bilineal acute leukemia because of the role of prosurvival BCL-2 proteins in resistance, their imbalanced expression in infant ALL, and evidence of obatoclax activity with a favorable toxicity profile in early adult leukemia trials. Overall, half maximal effective concentrations (EC50s) were lower than 176 nM (the maximal plasma concentration [Cmax] with recommended adult dose) in 76% of samples, whether in MLL-AF4, MLL-ENL, or other MLL-R or MLL-G subsets, and regardless of patients' poor prognostic features. However, MLL status and partner genes correlated with EC50. Combined approaches including flow cytometry, Western blot, obatoclax treatment with death pathway inhibition, microarray analyses, and/or electron microscopy indicated a unique killing mechanism involving apoptosis, necroptosis, and autophagy in MLL-AF4 ALL cell lines and primary MLL-R and MLL-G infant ALL cells. This in vitro obatoclax activity and its multiple killing mechanisms across molecular cytogenetic subsets provide a rationale to incorporate a similarly acting compound into combination strategies to combat infant ALL.

[Impact of evening exercise on college students' sleep quality].

OBJECTIVE: To investigate the impact of college students' evening exercise on their sleep quality, so as to provide a scientific basis for college students to choose an appropriate method of exercise and improve their sleep quality. METHODS: From September to October in 2012, Multi-stage cluster random sampling method was used to select the 5997 college students in Anhui province. The status of college students' exercise and their sleep quality were investigated by the general situation questionnaire, Physical activity rating scale-3(PARS-3), Rating of perceived exertion(RPE) and Pittsburgh sleep quality index(PSQI). Kruskal-Wallis test was used to analyze the impact of evening exercise on sleep quality and multivariate unconditional logistic regression was used to analyze the factors of sleep quality in evening excise students. RESULTS: The median of PSQI total score among 5806 college students was 5 and 1030(17.7%) students had poor sleep quality. The median of the PSQI scores was the same (5 points) for evening exercise group, daytime exercise group,daytime and evening exercise group and non-exercise group (1406, 1514, 1244, 1642 respectively). The difference was not statistically significant (χ(2) = 2.80, P = 0.42). Compared to non-exercise population, the OR (95%CI) value of evening exercise' impact on sleep quality was 0.90(0.73-1.10). Compared to very light evening exercise, the OR (95%CI) value of moderate and large amount of evening exercise' impact on sleep quality was 0.58 (0.44-0.75) and 0.67 (0.48-0.93) respectively; Compared to other sports, the OR (95%CI) value of badminton, rope skipping and jogging' impact on sleep quality was 0.72 (0.55-0.93), 0.38 (0.21-0.70) and 0.76 (0.60-0.95) respectively and they were all protective factors of sleep quality. Compared to small exercise intensity, the OR (95%CI) value of moderate, vigorous and very vigorous exercise intensity' impact on sleep quality was 1.68 (1.13-2.52), 2.38 (1.48-3.83) and 3.18 (1.72-5.90) respectively and they were harmful factors of sleep quality. CONCLUSION: There was no impact of evening exercise on sleep quality for college students. Type of sports should be adequately chosen for evening exercise. College students can take moderate and large amount of evening exercise but should avoid activities of vigorous intensity.

Klf4 overexpression activates epithelial cytokines and inflammation-mediated esophageal squamous cell cancer in mice.

BACKGROUND & AIMS: Esophageal squamous cell cancer accounts for more than 90% of cases of esophageal cancers. Its pathogenesis involves chronic epithelial irritation, although the factors involved in the inflammatory process and the mechanisms of carcinogenesis are unknown. We sought to develop a mouse model of this cancer. METHODS: We used the ED-L2 promoter of Epstein-Barr virus to overexpress the transcriptional regulator Krüppel-like factor 4 (Klf4) in esophageal epithelia of mice; we used mouse primary esophageal keratinocytes to examine the mechanisms by which KLF4 induces cytokine production. RESULTS: KLF4 was an epithelial-specific mediator of inflammation; we developed a new mouse model of esophageal squamous dysplasia and inflammation-mediated squamous cell cancer. KLF4 activated a number of proinflammatory cytokines, including TNF-α, CXCL5, G-CSF and IL-1α, within keratinocytes in an NF-κB-dependent manner. KLF4 was not detected in proliferating or cancer cells, indicating a non-cell autonomous effect of KLF4 on proliferation and carcinogenesis. CONCLUSIONS: KLF4 has distinct functions in carcinogenesis; upregulation of Klf4 specifically in esophageal epithelial cells induces inflammation. This mouse model might be used to determine the molecular mechanisms of esophageal squamous cell cancer and inflammation-mediated carcinogenesis.

Esophageal squamous cell dysplasia and delayed differentiation with deletion of krüppel-like factor 4 in murine esophagus.

BACKGROUND & AIMS: Krüppel-like factor 4 (Klf; previously known a gut-enriched Krüppel-like factor) is a DNA-binding transcriptional regulator highly expressed in skin and gastrointestinal epithelia, specifically in regions of cellular differentiation. Homozygous null mice for Klf4 die shortly after birth from skin defects, precluding their analysis at later stages. The aim of this study was to analyze the function of Klf4 in keratinocyte biology and epithelial homeostasis in the adult by focusing on the squamous lined esophagus. METHODS: By using the ED-L2 promoter of Epstein-Barr virus to drive Cre, we obtained tissue-specific ablation of Klf4 in the squamous epithelia of the tongue, esophagus, and forestomach. RESULTS: Mice with loss of Klf4 in esophageal epithelia survived to adulthood, bypassing the early lethality. Tissue-specific Klf4 knockout mice had increased basal cell proliferation and a delay in cellular maturation; these mice developed epithelial hypertrophy and subsequent dysplasia by 6 months of age. Moreover, loss of Klf4 in vivo was associated with increased expression of the pro-proliferative Klf5, and Klf4 down-regulated Klf5 both transcriptionally and posttranscriptionally. By using gene expression profiling, we also showed decreased expression of critical late-stage differentiation factors and identified alterations of several genes important in cellular differentiation. CONCLUSIONS: Klf4 is essential for squamous epithelial differentiation in vivo and interacts with Klf5 to maintain normal epithelial homeostasis.

Human cytomegalovirus uses two distinct pathways to enter retinal pigmented epithelial cells.

Human cytomegalovirus infects multiple cell types, including fibroblasts and epithelial cells. It penetrates fibroblasts by fusion at the cell surface but is endocytosed into epithelial cells. In this report, we demonstrate by electron microscopy that the virus uses two different routes to enter retinal pigmented epithelial cells, depending on the cell type in which the infecting virus was produced. Virus produced in epithelial cells preferentially fuses with the plasma membrane, whereas fibroblast-derived virus mostly enters by receptor-mediated endocytosis. Treatment of epithelial cells with agents that block endosome acidification inhibited infection by virus produced in fibroblasts but had only a modest effect on infection by virus from epithelial cells. Epithelial cell-generated virions had higher intrinsic "fusion-from-without" activity than fibroblast-generated particles, and the two virus preparations triggered different cellular signaling responses, as evidenced by markedly different transcriptional profiles. We propose that the cell type in which a human cytomegalovirus particle is produced likely influences its subsequent spread and its contribution to pathogenesis.

Bax and Bak can localize to the endoplasmic reticulum to initiate apoptosis.

Bax and Bak play a redundant but essential role in apoptosis initiated by the mitochondrial release of apoptogenic factors. In addition to their presence at the mitochondrial outer membrane, Bax and Bak can also localize to the ER. Agents that initiate ER stress responses can induce conformational changes and oligomerization of Bax on the ER as well as on mitochondria. In wild-type cells, this is associated with caspase 12 cleavage that is abolished in bax-/-bak-/- cells. In bax-/-bak-/- cells, introduction of Bak mutants selectively targeted to either mitochondria or the ER can induce apoptosis. However, ER-targeted, but not mitochondria-targeted, Bak leads to progressive depletion of ER Ca2+ and induces caspase 12 cleavage. In contrast, mitochondria-targeted Bak leads to enhanced caspase 7 and PARP cleavage in comparison with the ER-targeted Bak. These findings demonstrate that in addition to their functions at mitochondria, Bax and Bak also localize to the ER and function to initiate a parallel pathway of caspase activation and apoptosis.

Tumor cell alpha3beta1 integrin and vascular laminin-5 mediate pulmonary arrest and metastasis.

Arrest of circulating tumor cells in distant organs is required for hematogenous metastasis, but the tumor cell surface molecules responsible have not been identified. Here, we show that the tumor cell alpha3beta1 integrin makes an important contribution to arrest in the lung and to early colony formation. These analyses indicated that pulmonary arrest does not occur merely due to size restriction, and raised the question of how the tumor cell alpha3beta1 integrin contacts its best-defined ligand, laminin (LN)-5, a basement membrane (BM) component. Further analyses revealed that LN-5 is available to the tumor cell in preexisting patches of exposed BM in the pulmonary vasculature. The early arrest of tumor cells in the pulmonary vasculature through interaction of alpha3beta1 integrin with LN-5 in exposed BM provides both a molecular and a structural basis for cell arrest during pulmonary metastasis.

The 16 kDa subunit of vacuolar H+-ATPase is a novel sarcoglycan-interacting protein.

The sarcoglycan complex in muscle consists of alpha-, beta-, gamma- and delta-sarcoglycan and is part of the larger dystrophin-glycoprotein complex (DGC), which is essential for maintaining muscle membrane integrity. Mutations in any of the four sarcoglycans cause limb-girdle muscular dystrophies (LGMD). In this report, we have identified a novel interaction between delta-sarcoglycan and the 16 kDa subunit c (16K) of vacuolar H(+)-ATPase. Co-expression studies in heterologous cell system revealed that 16K interacts specifically with delta-sarcoglycan and the highly related gamma-sarcoglycan through the transmembrane domains. In cultured C2C12 myotubes, 16K forms a complex with sarcoglycans at the plasma membrane. Loss of sarcoglycans in the sarcoglycan-deficient BIO14.6 hamster destabilizes the DGC and alters the localization of 16K at the sarcolemma. In addition, the steady state level of beta(1)-integrin is increased. Recent studies have shown that 16K also interacts directly with beta(1)-integrin and our data demonstrated that sarcoglycans, 16K and beta(1)-integrin were immunoprecipitated together in C2C12 myotubes. Since sarcoglycans have been proposed to participate in bi-directional signaling with integrins, our findings suggest that 16K might mediate the communication between sarcoglycans and integrins and play an important role in the pathogenesis of muscular dystrophy.

Cardiomyocyte-specific deletion of the coxsackievirus and adenovirus receptor results in hyperplasia of the embryonic left ventricle and abnormalities of sinuatrial valves.

The coxsackievirus and adenovirus receptor (CAR), which mediates infection by the viruses most commonly associated with myocarditis, is a transmembrane component of specialized intercellular junctions, including the myocardial intercalated disc; it is known to mediate cell-cell recognition, but its natural function is poorly understood. We used conditional gene targeting to investigate the possible functions of CAR during embryonic development, generating mice with both germline and tissue-specific defects in CAR expression. Homozygous germline deletion of CAR exon 2 or cardiomyocyte-specific gene deletion at embryonic day 10 (E10) mediated by Cre recombinase expressed under the control of the cardiac troponin T promoter resulted in death by E12.5; embryos showed marked cardiac abnormalities by E10.5, with hyperplasia of the left ventricular myocardium, distention of the cardinal veins, and abnormalities of sinuatrial valves. Within the hyperplastic left ventricle, increased numbers of proliferating cells were evident; persistent expression of N-myc in the hyperplastic myocardium and attenuated expression of the trabecular markers atrial natriuretic factor and bone morphogenic protein 10 indicated that proliferating cardiomyocytes had failed to differentiate and form normal trabeculae. In electron micrographs, individual CAR-deficient cardiomyocytes within the left ventricle appeared normal, but intercellular junctions were ill-formed or absent, consistent with the known function of CAR as a junctional molecule; myofibrils were also poorly organized. When cardiomyocyte-specific deletion occurred somewhat later (by E11, mediated by Cre under control of the alpha-myosin heavy chain promoter), animals survived to adulthood and did not have evident cardiac abnormalities. These results indicate that during a specific temporal window, CAR expression on cardiomyocytes is essential for normal cardiac development. In addition, the results suggest that CAR-mediated intercellular contacts may regulate proliferation and differentiation of cardiomyocytes within the embryonic left ventricular wall.

Utility of PEGylated recombinant adeno-associated viruses for gene transfer.

Adeno-associated virus (AAV), capable of producing significant, long-term transgene expression, is one of the least toxic vectors employed in pre-clinical and clinical studies of gene transfer. One limitation is generation of neutralizing antibodies against viral capsids, blocking gene expression after readministration. AAV2 capsids were modified with poly(ethylene) glycols (PEGs) activated by cyanuric chloride (CCPEG), succinimidyl succinate (SSPEG) and tresyl chloride (TMPEG). SSPEG and TMPEG conjugation did not compromise gene transfer to the liver and muscle and improved gene expression in the lung 5 fold. Transduction efficiency of CCPEG-AAV was impeded in all tissues by aggregation. TMPEG afforded the best protection from neutralization in vitro and in vivo. Gene expression in mice immunized against unmodified AAV was reduced by a factor of 10 from that of naïve animals after intramuscular rechallenge with PEGylated AAV but was not significantly different from naïve mice after intravenous readministration (p=0.08). Gene expression was markedly reduced in muscle after two doses of PEGylated AAV. In contrast, mice given two intravenous doses of TMPEG-AAV had significantly higher transgene levels than naïve animals 14 days after rechallenge (p=0.001). This technology could promote successful readministration of vector in the clinic and marked expression in patients with anti-AAV antibodies.

Combined 5-fluorouracil/systemic interferon-beta gene therapy results in long-term survival in mice with established colorectal liver metastases.

Preclinical in vitro and in vivo studies have demonstrated synergistic interactions between 5-fluorouracil (5-FU) and type I and II IFNs against human colorectal cancer cells. Despite these activities, randomized human trials have failed to identify a clinical benefit for this combination treatment. These limited clinical results may be secondary to the short half-life of recombinant IFN protein and the increased systemic toxicities of 5-FU/IFN combinations. We have previously reported an adenoviral-mediated IFN-beta gene therapy strategy, which may circumvent the pitfalls of recombinant IFN therapy. However, a dose-dependent toxicity and acute inflammatory response to systemically administered adenovirus vectors may limit the clinical application of this therapy. The combination of adenoviral-mediated IFN-beta gene therapy and 5-FU resulted in tumor regression, apoptosis, and improved survival in an established liver metastases model. These therapeutic effects were observed at a significantly lower vector dose than we had previously reported and with limited toxicity. This approach may allow for an effective clinical application of this therapy and warrants additional investigation.

Lack of the vitamin D receptor is associated with reduced epidermal differentiation and hair follicle growth.

The active vitamin D metabolite, 1,25-dihydroxyvitamin D, acting through the vitamin D receptor, regulates the expression of genes in a variety of vitamin D-responsive tissues, including the epidermis. To investigate the role of the vitamin D receptor in mediating epidermal differentiation, we examined the histomorphology and expression of differentiation markers in the epidermis of vitamin D receptor knockout mice generated by gene targeting. The homozygous knockout mouse displayed a phenotype that closely resembles vitamin D-dependent rickets type II in humans, including the development of rickets and alopecia. Hair loss developed by 3 mo after birth and gradually led to nearly total hair loss by 8 mo. Histologic analysis of the skin of homozygous knockout mice revealed dilation of the hair follicles with the formation of dermal cysts starting at the age of 3 wk. These cysts increased in size and number with age. Epidermal differentiation markers, including involucrin, profilaggrin, and loricrin, detected by immunostaining and in situ hybridization, showed decreased expression levels in homozygous knockout mice from birth until 3 wk, preceding the morphologic changes observed in the hair follicles. Keratin 10 levels, however, were not reduced. At the ultrastructural level, homozygous knockout mice showed increased numbers of small dense granules in the granular layer with few or no surrounding keratin bundles and a loss of keratohyalin granules. Thus, both the interfollicular epidermis and the hair follicle appear to require the vitamin D receptor for normal differentiation. The temporal abnormalities between the two processes reflect the apparent lack of requirement for the vitamin D receptor during the anagen phase of the first (developmental) hair cycle, but with earlier effects on the terminal differentiation of the interfollicular epidermis.

Role of peroxisome proliferator-activated receptor alpha in epidermal development in utero.

The protective function of the skin is mediated by the stratum corneum, the outermost layer of the skin, which is the end-product of epidermal differentiation. Previously, we showed that fetal rat skin explants complete the late-stage milestones of epidermal development when grown in a serum- and growth-factor-free medium, suggesting that endogenous metabolites could regulate the late program that leads to barrier formation. Because a variety of endogenous free fatty acids are known activators, peroxisome proliferator-activated receptor alpha (PPAR-alpha) is a potential candidate for this key regulatory role. Indeed, whereas PPAR-alpha expression is first noted at gestational day 13.5 and peaks between days 14.5 and 15.5, fatty acid synthesis is very active in fetal rodent epidermis peaking at gestational day 17. Furthermore, we have reported that both epidermal differentiation and stratum corneum formation in utero are stimulated by pharmacologic activation of PPAR-alpha. This study was designed to test whether PPAR-alpha plays a physiologic role in epidermal differentiation and stratum corneum formation in utero. In PPAR-alpha-/- mice we observed delayed stratum corneum formation between day 18.5 of gestation and birth. Concurrently, there was diminished beta-glucocerebrosidase activity at the stratum granulosum-stratum corneum junction and a modest decrease in both involucrin and loricrin protein expression, markers of keratinocyte differentiation. Both the number of stratum corneum cell layers was reduced and the processing of the lamellar bilayers was delayed in animals lacking PPAR-alpha, indicating a transient functional defect. In contrast, the lamellar body secretory system as well as rates of epidermal proliferation and cell death appeared normal in PPAR-alpha-/- mice. These results indicate that PPAR-alpha plays a physiologic role during fetal stratum corneum development. The transient and incomplete nature of the developmental delay, however, is consistent with regulation of the late stages of epidermal development by multiple factors.

Transcriptional mechanisms link epithelial plasticity to adhesion and differentiation of epidermal progenitor cells.

During epithelial tissue morphogenesis, developmental progenitor cells undergo dynamic adhesive and cytoskeletal remodeling to trigger proliferation and migration. Transcriptional mechanisms that restrict such a mild form of epithelial plasticity to maintain lineage-restricted differentiation in committed epithelial tissues are poorly understood. Here, we report that simultaneous ablation of transcriptional repressor-encoding Ovol1 and Ovol2 results in expansion and blocked terminal differentiation of embryonic epidermal progenitor cells. Conversely, mice overexpressing Ovol2 in their skin epithelia exhibit precocious differentiation accompanied by smaller progenitor cell compartments. We show that Ovol1/Ovol2-deficient epidermal cells fail to undertake α-catenin-driven actin cytoskeletal reorganization and adhesive maturation and exhibit changes that resemble epithelial-to-mesenchymal transition (EMT). Remarkably, these alterations and defective terminal differentiation are reversed upon depletion of EMT-promoting transcriptional factor Zeb1. Collectively, our findings reveal Ovol-Zeb1-α-catenin sequential repression and highlight Ovol1 and Ovol2 as gatekeepers of epithelial adhesion and differentiation by inhibiting progenitor-like traits and epithelial plasticity.

[Study on the relationship between college students' physical quality and the quality of sleep].

OBJECTIVE: The author wants to investigate the relationship between college students' physical quality and the quality of sleep. METHODS: Stratified cluster sampling method is used, and invites a total of 2981 Anhui college students to take part in the questionnaire study, the Pittsburgh sleep quality index (PSQI) and physical test, in order to survey the sleep quality and physical quality of college students. The physical quality and sleep quality are analyzed by the multiple factor non conditional logistic regression analysis methods. RESULTS: PSQI scores of the 2744 students are (5.378 ± 2.492), 477 people (17.4%) have poor sleep quality. The endurance, speed, strength quality scores are (75.850 ± 13.279), (69.760 ± 16.422), (66.278 ± 18.709) points. Logistic regression analysis shows that excellent endurance (OR = 0.418) is a protective factor of sleep quality. CONCLUSION: The improvement of endurance may improve sleep quality.

PERK is required in the adult pancreas and is essential for maintenance of glucose homeostasis.

Germ line PERK mutations are associated with diabetes mellitus and growth retardation in both rodents and humans. In contrast, late embryonic excision of PERK permits islet development and was found to prevent onset of diabetes, suggesting that PERK may be dispensable in the adult pancreas. To definitively establish the functional role of PERK in adult pancreata, we generated mice harboring a conditional PERK allele in which excision is regulated by tamoxifen administration. Deletion of PERK in either young adult or mature adult mice resulted in hyperglycemia associated with loss of islet and ß cell architecture. PERK excision triggered intracellular accumulation of proinsulin and Glut2, massive endoplasmic reticulum (ER) expansion, and compensatory activation of the remaining unfolded-protein response (UPR) signaling pathways specifically in pancreatic tissue. Although PERK excision increased ß cell death, this was not a result of decreased proliferation as previously reported. In contrast, a significant and specific increase in ß cell proliferation was observed, a result reflecting increased cyclin D1 accumulation. This work demonstrates that contrary to expectations, PERK is required for secretory homeostasis and ß cell survival in adult mice.

The von Hippel-Lindau Chuvash mutation promotes pulmonary hypertension and fibrosis in mice.

Mutation of the von Hippel-Lindau (VHL) tumor suppressor protein at codon 200 (R200W) is associated with a disease known as Chuvash polycythemia. In addition to polycythemia, Chuvash patients have pulmonary hypertension and increased respiratory rates, although the pathophysiological basis of these symptoms is unclear. Here we sought to address this issue by studying mice homozygous for the R200W Vhl mutation (VhlR/R mice) as a model for Chuvash disease. These mice developed pulmonary hypertension independently of polycythemia and enhanced normoxic respiration similar to Chuvash patients, further validating VhlR/R mice as a model for Chuvash disease. Lungs from VhlR/R mice exhibited pulmonary vascular remodeling, hemorrhage, edema, and macrophage infiltration, and lungs from older mice also exhibited fibrosis. HIF-2alpha activity was increased in lungs from VhlR/R mice, and heterozygosity for Hif2a, but not Hif1a, genetically suppressed both the polycythemia and pulmonary hypertension in the VhlR/R mice. Furthermore, Hif2a heterozygosity resulted in partial protection against vascular remodeling, hemorrhage, and edema, but not inflammation, in VhlR/R lungs, suggesting a selective role for HIF-2alpha in the pulmonary pathology and thereby providing insight into the mechanisms underlying pulmonary hypertension. These findings strongly support a dependency of the Chuvash phenotype on HIF-2alpha and suggest potential treatments for Chuvash patients.

"Free-floating" desmosomes in lipoid proteinosis: an inherent defect in keratinocyte adhesion?

The classic features of lipoid proteinosis - beadlike papules and hoarseness - result from the accumulation of hyaline material in the mucocutaneous dermis. However, the characteristic manifestation in children - erosive, crusted lesions that lead to scarring - is rarely discussed and poorly understood. Lipoid proteinosis results from mutations in extracellular matrix protein 1, but the function of this protein is largely unknown. We performed ultrastructural studies on lesional epidermis, cultured monolayer keratinocytes, and raft keratinocyte cultures from blistering lesions of a child with lipoid proteinosis. All sections showed the dissociation of relatively intact desmosomes from keratinocytes, with desmosomes that were "free-floating" in the intercellular spaces or attached by thin strands to the cell membrane. These changes were present in serial sections of both tissue and cultured keratinocytes, suggesting this observation to be an inherent feature of keratinocytes devoid of extracellular matrix protein 1, rather than an artifact. Although additional patients should be studied, the diminished appearance of the inner dense plaque - the region of attachment of keratin intermediate filaments to desmosomal proteins - provides preliminary evidence that extracellular matrix protein 1 may participate in attaching keratin intermediate filaments to desmosomal region protein(s).

Lactosylated poly-L-lysine targets a potential lactose receptor in cystic fibrosis and non-cystic fibrosis airway epithelial cells.

Poly-L-lysine with 40% of the epsilon -amino groups substituted with lactosyl residues facilitated the internalization of lactosylated poly-L-lysine/cDNA complexes into cystic fibrosis (CF) and non-CF airway epithelial cells. It was previously shown that lactosylated poly-L-lysine enhanced the transfer of cDNA into the cell nucleus, resulting in transfection. The cell entry of lactosylated poly-L-lysine/cDNA complexes, however, has not been elucidated and we hypothesized that entry of the complex was by receptor-mediated endocytosis. It is shown here that binding of the vector/cDNA complexes to the cell membrane was inhibited by lactose but not N-acetyl glucosamine. Examination by electron microscopy revealed the complexes in clathrin-coated pits. Furthermore, the complexes colocalized with transferrin during cell entry and were shown in early endosomes. These results demonstrated that lactosylated poly-L-lysine/cDNA complexes enter airway epithelial cells via receptor-mediated endocytosis utilizing lactose-binding receptors, which employ the clathrin-coated pit for internalization. Taken together with the fact that nuclear translocation also is enhanced by lactose, these results demonstrate why lactosylated poly-L-lysine is an excellent vector for transfection of airway epithelial cells. Moreover, other carbohydrates covalently linked to poly-L-lysine for targeting other specific cell types, combined with lactosyl residues, can be designed for the development of other molecular conjugates for gene transfer.