Phosphoglucose isomerase/autocrine motility factor promotes melanoma cell migration through ERK activation dependent on autocrine production of interleukin-8

RHBDF1 deficiency suppresses melanoma glycolysis and enhances efficacy of immunotherapy by facilitating glucose-6-phosphate isomerase degradation via TRIM32

Melanoma is a dangerous form of skin cancer, making it important to investigate new mechanisms and approaches to enhance the effectiveness of treatment. Here, we establish a positive correlation between the human rhomboid family-1 (RHBDF1) protein and melanoma malignancy. We demonstrate that the melanoma RHBDF1 decrease dramatically inhibits tumor growth and the development of lung metastases, which may be related to the impaired glycolysis. We show that RHBDF1 function is essential to the maintenance of high levels of glycolytic enzymes, especially glucose-6-phosphate isomerase (GPI). Additionally, we discover that the E3 ubiquitin ligase tripartite motif-containing 32 (TRIM32) mediates the K27/K63-linked ubiquitination of GPI and the ensuing lysosomal degradation process. We prove that the multi-transmembrane domain of RHBDF1 is in competition with GPI, preventing the latter from interacting with NCL1-HT2A-LIN41 (NHL) domain of TRIM32. We also note that the mouse RHBDF1's R747 and Y799 are crucial for competitive binding and GPI protection. Artificially silencing the Rhbdf1 gene in a mouse melanoma model results in declined lactic acid levels, elevated cytotoxic lymphocyte infiltration, and improved tumor responsiveness to immunotherapy. These results provide credence to the hypothesis that RHBDF1 plays a significant role in melanoma regulation and suggest that blocking RHBDF1 may be an efficient technique for reestablishing the tumor immune microenvironment (TIME) in melanoma and halting its progression.

The role of tumor microenvironment on cancer stem cell fate in solid tumors

In the last few decades, the role of cancer stem cells in initiating tumors, metastasis, invasion, and resistance to therapies has been recognized as a potential target for tumor therapy. Understanding the mechanisms by which CSCs contribute to cancer progression can help to provide novel therapeutic approaches against solid tumors. In this line, the effects of mechanical forces on CSCs such as epithelial-mesenchymal transition, cellular plasticity, etc., the metabolism pathways of CSCs, players of the tumor microenvironment, and their influence on the regulating of CSCs can lead to cancer progression. This review focused on some of these mechanisms of CSCs, paving the way for a better understanding of their regulatory mechanisms and developing platforms for targeted therapies. While progress has been made in research, more studies will be required in the future to explore more aspects of how CSCs contribute to cancer progression. Video Abstract.

Evidence for Recombinant GRP78, CALR, PDIA3 and GPI as Mediators of Genetic Instability in Human CD34+ Cells

Soluble factors released from irradiated human mesenchymal stromal cells (MSC) may induce genetic instability in human CD34+ cells, potentially mediating hematologic disorders. Recently, we identified four key proteins in the secretome of X-ray-irradiated MSC, among them three endoplasmic reticulum proteins, the 78 kDa glucose-related protein (GRP78), calreticulin (CALR), and protein disulfide-isomerase A3 (PDIA3), as well as the glycolytic enzyme glucose-6-phosphate isomerase (GPI). Here, we demonstrate that exposition of CD34+ cells to recombinant GRP78, CALR, PDIA3 and GPI induces substantial genetic instability. Increased numbers of γH2AX foci (p < 0.0001), centrosome anomalies (p = 0.1000) and aberrant metaphases (p = 0.0022) were detected in CD34+ cells upon incubation with these factors. Specifically, γH2AX foci were found to be induced 4−5-fold in response to any individual of the four factors, and centrosome anomalies by 3−4 fold compared to control medium, which contained none of the recombinant proteins. Aberrant metaphases, not seen in the context of control medium, were detected to a similar extent than centrosome anomalies across the four factors. Notably, the strongest effects were observed when all four factors were collectively provided. In summary, our data suggest that specific components of the secretome from irradiated MSC act as mediators of genetic instability in CD34+ cells, thereby possibly contributing to the pathogenesis of radiation-induced hematologic disorders beyond direct radiation-evoked DNA strand breaks.

Proteins Marking the Sequence of Genotoxic Signaling from Irradiated Mesenchymal Stromal Cells to CD34+ Cells

Non-targeted effects (NTE) of ionizing radiation may initiate myeloid neoplasms (MN). Here, protein mediators (I) in irradiated human mesenchymal stromal cells (MSC) as the NTE source, (II) in MSC conditioned supernatant and (III) in human bone marrow CD34+ cells undergoing genotoxic NTE were investigated. Healthy sublethal irradiated MSC showed significantly increased levels of reactive oxygen species. These cells responded by increasing intracellular abundance of proteins involved in proteasomal degradation, protein translation, cytoskeleton dynamics, nucleocytoplasmic shuttling, and those with antioxidant activity. Among the increased proteins were THY1 and GNA11/14, which are signaling proteins with hitherto unknown functions in the radiation response and NTE. In the corresponding MSC conditioned medium, the three chaperones GRP78, CALR, and PDIA3 were increased. Together with GPI, these were the only four altered proteins, which were associated with the observed genotoxic NTE. Healthy CD34+ cells cultured in MSC conditioned medium suffered from more than a six-fold increase in γH2AX focal staining, indicative for DNA double-strand breaks, as well as numerical and structural chromosomal aberrations within three days. At this stage, five proteins were altered, among them IQGAP1, HMGB1, and PA2G4, which are involved in malign development. In summary, our data provide novel insights into three sequential steps of genotoxic signaling from irradiated MSC to CD34+ cells, implicating that induced NTE might initiate the development of MN.

The positive correlation between drug addiction and drug dosage in vemurafenib-resistant melanoma cells is underpinned by activation of ERK1/2-FRA-1 pathway

Malignant melanoma is a kind of highly invasive and deadly diseases. The BRAF inhibitor (BRAFi) such as vemurafenib could achieve a high response rate in melanoma patients with BRAF mutation. However, melanoma cells could easily develop resistance as well as addiction to BRAFi. Based on the drug addiction, intermittent treatment has been proposed to select against BRAFi-resistant melanoma cells. Because different dosages of BRAFi might be used in patients, it is necessary to know about the relationship between drug dosage and the degree of addiction. To address the problem, four drug-resistant melanoma cell sublines (A375/R0.5, A375/R2.0, M14/R0.5 and M14/R2.0) were established by continuously exposure of melanoma A375 or M14 cells to 0.5 or 2.0 μM vemurafenib. Vemurafenib withdrawal resulted in much stronger suppression on clone formation in A375/R2.0 and M14/R2.0, compared with A375/R0.5 and M14/R0.5, respectively. Meanwhile, stronger upregulation of ERK1/2-FRA-1 pathway could be observed in A375/R2.0 and M14/R2.0. Further detection showed that some proinflammatory cytokines downstream of ERK1/2-FRA-1 pathway were upregulated after drug withdrawal, and the conditioned medium collected from the resistant A375 cells could inhibit clone formation. Furthermore, vemurafenib withdrawal resulted in suppressed cell proliferation rather than cell senescence, with stronger effect on A375/R2.0 compared with A375/R0.5. This study suggested that the depth of vemurafenib addiction in resistant melanoma cells is positively correlated to the drug dosage, which might be underpinned by the ERK1/2-FRA-1 pathway and the related cytokines.

Cutaneous melanoma dissemination is dependent on the malignant cell properties and factors of intercellular crosstalk in the cancer microenvironment (Review)

The incidence of cutaneous malignant melanoma has been steadily increasing worldwide for several decades. This phenomenon seems to follow the trend observed in many types of malignancies caused by multiple significant factors, including ageing. Despite the progress in cutaneous malignant melanoma therapeutic options, the curability of advanced disease after metastasis represents a serious challenge for further research. In this review, we summarise data on the microenvironment of cutaneous malignant melanoma with emphasis on intercellular signalling during the disease progression. Malignant melanocytes with features of neural crest stem cells interact with non‑malignant populations within this microenvironment. We focus on representative bioactive factors regulating this intercellular crosstalk. We describe the possible key factors and signalling cascades responsible for the high complexity of the melanoma microenvironment and its premetastatic niches. Furthermore, we present the concept of melanoma early becoming a systemic disease. This systemic effect is presented as a background for the new horizons in the therapy of cutaneous melanoma.

Hydroxyapatite mineral enhances malignant potential in a tissue-engineered model of ductal carcinoma in situ (DCIS)

While ductal carcinoma in situ (DCIS) is known as a precursor lesion to most invasive breast carcinomas, the mechanisms underlying this transition remain enigmatic. DCIS is typically diagnosed by the mammographic detection of microcalcifications (MC). MCs consisting of non-stoichiometric hydroxyapatite (HA) mineral are frequently associated with malignant disease, yet it is unclear whether HA can actively promote malignancy. To investigate this outstanding question, we compared phenotypic outcomes of breast cancer cells cultured in control or HA-containing poly(lactide-co-glycolide) (PLG) scaffolds. Exposure to HA mineral in scaffolds increased the expression of pro-tumorigenic interleukin-8 (IL-8) among transformed but not benign cells. Notably, MCF10DCIS.com cells cultured in HA scaffolds adopted morphological changes associated with increased invasiveness and exhibited increased motility that were dependent on IL-8 signaling. Moreover, MCF10DCIS.com xenografts in HA scaffolds displayed evidence of enhanced malignant progression relative to xenografts in control scaffolds. These experimental findings were supported by a pathological analysis of clinical DCIS specimens, which correlated the presence of MCs with increased IL-8 staining and ductal proliferation. Collectively, our work suggests that HA mineral may stimulate malignancy in preinvasive DCIS cells and validate PLG scaffolds as useful tools to study cell-mineral interactions.

Higher autocrine motility factor/glucose-6-phosphate isomerase expression is associated with tumorigenesis and poorer prognosis in gastric cancer

Background

Glucose-6-phosphate isomerase (GPI) is a glycolytic-related enzyme that inter-converts glucose-6-phosphate and fructose-6-phosphate in the cytoplasm. This protein is also secreted into the extracellular matrix by cancer cells and is, therefore, also called autocrine motility factor (AMF).

Methods

To clarify the roles of AMF/GPI in gastric cancer (GC), we collected 335 GC tissues and the corresponding adjacent noncancerous tissues, performed immunohistochemical studies, and analyzed the relationship between AMF/GPI expression and the patients’ clinicopathologic features.

Results

AMF/GPI expression was found to be significantly higher in the GC group than in the corresponding noncancerous tissue group (P<0.001). Additionally, AMF/GPI expression positively associated with a higher TNM stage and poorer prognosis in patients. Through Kaplan–Meier analysis and according to the Oncomine database, we found that AMF/GPI was overexpressed in GC tissues compared to normal mucosa, and the patients with higher AMF/GPI expression had poorer outcomes. We used AMF/GPI-silenced GC cell lines to observe how changes in AMP/GPI affect cellular phenotypes. AMF/GPI knockdown suppressed proliferation, migration, invasion, and glycolysis, and induced apoptosis in GC cells.

Conclusion

These findings suggest that AMF/GPI overexpression is involved in carcinogenesis and promotes the aggressive phenotypes of GC cells.

Functional interplay between secreted ligands and receptors in melanoma

Melanoma, the most aggressive form of skin cancer, results from the malignant transformation of melanocytes located in the basement membrane separating the epidermal and dermal skin compartments. Cutaneous melanoma is often initiated by solar ultraviolet radiation (UVR)-induced mutations. Melanocytes intimately interact with keratinocytes, which provide growth factors and melanocortin peptides acting as paracrine regulators of proliferation and differentiation. Keratinocyte-derived melanocortins activate melanocortin-1 receptor (MC1R) to protect melanocytes from the carcinogenic effect of UVR. Accordingly, MC1R is a major determinant of susceptibility to melanoma. Despite extensive phenotypic heterogeneity and high mutation loads, the molecular basis of melanomagenesis and the molecules mediating the crosstalk between melanoma and stromal cells are relatively well understood. Mutations of intracellular effectors of receptor tyrosine kinase (RTK) signalling, notably NRAS and BRAF, are major driver events more frequent than mutations in RTKs. Nevertheless, melanomas often display aberrant signalling from RTKs such as KIT, ERRB1-4, FGFR, MET and PDGFR, which contribute to disease progression and resistance to targeted therapies. Progress has also been made to unravel the role of the tumour secretome in preparing the metastatic niche. However, key aspects of the melanoma-stroma interplay, such as the molecular determinants of dormancy, remain poorly understood.

Non-metabolic functions of glycolytic enzymes in tumorigenesis

Cancer cells reprogram their metabolism to meet the requirement for survival and rapid growth. One hallmark of cancer metabolism is elevated aerobic glycolysis and reduced oxidative phosphorylation. Emerging evidence showed that most glycolytic enzymes are deregulated in cancer cells and play important roles in tumorigenesis. Recent studies revealed that all essential glycolytic enzymes can be translocated into nucleus where they participate in tumor progression independent of their canonical metabolic roles. These noncanonical functions include anti-apoptosis, regulation of epigenetic modifications, modulation of transcription factors and co-factors, extracellular cytokine, protein kinase activity and mTORC1 signaling pathway, suggesting that these multifaceted glycolytic enzymes not only function in canonical metabolism but also directly link metabolism to epigenetic and transcription programs implicated in tumorigenesis. These findings underscore our understanding about how tumor cells adapt to nutrient and fuel availability in the environment and most importantly, provide insights into development of cancer therapy.

Microfluidics‑based optimization of neuroleukin‑mediated regulation of articular chondrocyte proliferation

Due to the low proliferative and migratory capacities of chondrocytes, cartilage repair remains a challenging clinical problem. Current therapeutic strategies for cartilage repair result in unsatisfactory outcomes. Autologous chondrocyte implantation (ACI) is a cell based therapy that relies on the in vitro expansion of healthy chondrocytes from the patient, during which proliferation-promoting factors are frequently used. Neuroleukin (NLK) is a multifunctional protein that possesses growth factor functions, and its expression has been associated with cartilage development and bone regeneration, however its direct role in chondrocyte proliferation remains to be fully elucidated. In the current study, the role of NLK in chondrocyte proliferation in vitro in addition to its potential to act as an exogenous factor during ACI was investigated. Furthermore, the concentration of NLK for in vitro chondrocyte culture was optimized using a microfluidic device. An NLK concentration of 12.85 ng/ml was observed to provide optimal conditions for the promotion of chondrocyte proliferation. Additionally, NLK stimulation resulted in an increase in type II collagen synthesis by chondrocytes, which is a cartilaginous secretion marker and associated with the phenotype of chondrocytes. Together these data suggest that NLK is able to promote cell proliferation and type II collagen synthesis during in vitro chondrocyte propagation, and thus may serve as an exogenous factor for ACI.

Neuroleukin/Autocrine Motility Factor Receptor Pathway Promotes Proliferation of Articular Chondrocytes through Activation of AKT and Smad2/3

Cartilage defect is an intractable clinical problem. Therapeutic strategies for cartilage repair are far from optimal due to poor proliferation capacity of chondrocytes. Autologous chondrocyte implantation is a cell based therapy that uses in vitro amplified healthy chondrocytes from the patient. However, chondrocyte dedifferentiation during in vitro culture limits its application. Neuroleukin (NLK) is a multifunctional protein that stimulates cell growth and migration, together with its receptor autocrine motility factor receptor (AMFR, also called gp78). We investigated expression of NLK and AMFR/gp78 during cartilage development in vivo and in cultured articular chondrocytes in vitro, and found the pair associates with chondrocyte proliferation and differentiation. While applied to isolated articular chondrocytes, NLK promotes cell proliferation and secretion of type II collagen, a marker of proliferating chondrocytes. Further work demonstrates that NLK up regulates pAKT and pSmad2/3, but down regulates pSmad1/5. In animals, NLK treatment also promotes chondrocyte proliferation while inhibits terminal differentiation, leading to expanded proliferating zone but decreased prehypertrophic and hypertrophic zones in the growth plate region. NLK is therefore a candidate factor that can be applied in the treatment of cartilage defects.

AMF/PGI-mediated tumorigenesis through MAPK-ERK signaling in endometrial carcinoma

Autocrine motility factor (AMF), which is also known as phosphoglucose isomerase (PGI), enhances tumor cell growth and motility. In this study, we found that AMF and its receptor were both highly expressed in Endometrial Carcinoma (EC) tissues compared to normal tissues. Levels of AMF were increased in serum of endometrial cancer patients. Downregulation of AMF by shRNA inhibited invasion, migration and proliferation as well as growth in a three-dimensional culture. AMF cytokine function, but not enzymatic activity of PGI, regulated tumorigenic activities of AMF. The MAPK-ERK1/2 pathway contributed to AMF-induced effects in EC cells. In agreement, Mek inhibitor decreased AMF-induced invasion, migration and proliferation of EC cells. In addition, in two mouse tumor metastasis models (EC cells delivered through left ventricle or intraperitoneally) AMF-silenced EC cells showed decreased tumor proliferative and metastatic capacities. We suggest that AMF/PGI is a potential therapeutic target in endometrial carcinoma.

How do glycolytic enzymes favour cancer cell proliferation by nonmetabolic functions?

Cancer cells enhance their glycolysis, producing lactate, even in the presence of oxygen. Glycolysis is a series of ten metabolic reactions catalysed by enzymes whose expression is most often increased in tumour cells. HKII and phosphoglucose isomerase (PGI) have mainly an antiapoptotic effect; PGI and glyceraldehyde-3-phosphate dehydrogenase activate survival pathways (Akt and so on); phosphofructokinase 1 and triose phosphate isomerase participate in cell cycle activation; aldolase promotes epithelial mesenchymal transition; PKM2 enhances various nuclear effects such as transcription, stabilisation and so on. This review outlines the multiple non-glycolytic roles of glycolytic enzymes, which are essential for promoting cancer cells' survival, proliferation, chemoresistance and dissemination.

How does cancer cell metabolism affect tumor migration and invasion?

Cancer metastasis is the major cause of cancer-associated death. Accordingly, identification of the regulatory mechanisms that control whether or not tumor cells become "directed walkers" is a crucial issue of cancer research. The deregulation of cell migration during cancer progression determines the capacity of tumor cells to escape from the primary tumors and invade adjacent tissues to finally form metastases. The ability to switch from a predominantly oxidative metabolism to glycolysis and the production of lactate even when oxygen is plentiful is a key characteristic of cancer cells. This metabolic switch, known as the Warburg effect, was first described in 1920s, and affected not only tumor cell growth but also tumor cell migration. In this review, we will focus on the recent studies on how cancer cell metabolism affects tumor cell migration and invasion. Understanding the new aspects on molecular mechanisms and signaling pathways controlling tumor cell migration is critical for development of therapeutic strategies for cancer patients.

Current and future trials of targeted therapies in cutaneous melanoma

In order to effectively treat melanoma, targeted inhibition of key m-echanistic events regulating melanoma development such as cell proliferation, survival, angiogenesis and invasion or metastasis needs to be accomplished. The Mitogen Activated Protein Kinase (MAPK) pathway has been identified as a key player in melanoma development making this cascade an important therapeutic target. However, identification of the ideal pathway member to therapeutically target for maximal clinical benefit remains a challenge. In normal cells, the MAPK pathway relays extracellular signals from the cell membrane to the nucleus via a cascade of phosphorylation events, which promote cancer development. Dysregulation of the MAPK pathway occurs frequently in many human cancers including melanoma. Mutations in the B-RAF and RAS genes, genetic or epigenetic modifications are the key aberrations observed in this signaling cascade. Constitutive activation of this pathway causes oncogenic transformation of cells by promoting cell proliferation, invasion, metastasis, migration, survival and angiogenesis. This review provides an overview of (a) key members of MAPK signaling regulating melanoma development; (b) key proteins which can serve as biomarkers to assess disease progression; (c) the clinical efficacy of various pharmacological agents targeting MAPK pathway; (d) current clinical trials evaluating downstream targets of the MAPK pathway; (e) issues associated with pharmacological agents such as drug resistance, induction of cancers; and finally (e) various strategies overcoming drug resistance.

Autocrine motility factor promotes HER2 cleavage and signaling in breast cancer cells

Trastuzumab (Herceptin) is an effective targeted therapy in HER2-overexpressing human breast carcinoma. However, many HER2-positive patients initially or eventually become resistant to this treatment, so elucidating mechanisms of trastuzumab resistance that emerge in breast carcinoma cells is clinically important. Here, we show that autocrine motility factor (AMF) binds to HER2 and induces cleavage to the ectodomain-deleted and constitutively active form p95HER2. Mechanistic investigations indicated that interaction of AMF with HER2 triggers HER2 phosphorylation and metalloprotease-mediated ectodomain shedding, activating phosphoinositide-3-kinase (PI3K) and mitogen-activated protein kinase signaling and ablating the ability of trastuzumab to inhibit breast carcinoma cell growth. Furthermore, we found that HER2 expression and AMF secretion were inversely related in breast carcinoma cells. On the basis of this evidence that AMF may contribute to HER2-mediated breast cancer progression, our findings suggest that AMF-HER2 interaction might be a novel target for therapeutic management of patients with breast cancer, whose disease is resistant to trastuzumab.

Interleukin-8 (CXCL8) in tumor associated non-vascular extracellular fluids: its diagnostic and prognostic values. A review

Interleukin-8 (IL-8, CXCL8) was originally discovered as a powerful attractor and activator of polymorphonuclear leukocytes. It was soon recognized that IL-8 also affects proliferation and migration of cancer cells, tumor angiogenesis and metastasis, and that it is expressed in many cancerous cell types. IL-8 protein expression is usually increased in serum of cancer patients, but markedly higher concentrations are found in cancer-associated non-vascular extracellular fluids, such as pleural effusion, ascites and cyst fluid. Elevated concentrations of IL-8 are indicative of malignant processes also in cerebrospinal fluid, urine, saliva, interstitial fluid and cervicovaginal secretions. Higher IL-8 levels are typically found in high-grade peritumoral fluids rather than low-grade tumors and benign conditions, with the exception of inflammatory processes. In line with recent molecular biology investigations, it appears that the local IL-8 production is related to its malignant origin and to tumor progression. Hence, IL-8 in peritumoral fluid is to be taken into consideration while assessing tumor character and monitoring the tumor progression/remission status. Besides, the data here collected justify the attempts to find an IL-8-targeted inhibitory therapy

Interleukin-8 associates with adhesion, migration, invasion and chemosensitivity of human gastric cancer cells

AIM: To investigate the relationship between Interleukin-8 (IL-8) and proliferation, adhesion, migration, invasion and chemosensitivity of gastric cancer (GC) cells.

METHODS: The IL-8 cDNA was stably transfected into human GC cell line MKN-45 and selected IL-8-secreting transfectants. The expression of IL-8 in human GC cell line KATO-III was inhibited by RNA interference. The expressions of mRNA and protein of IL-8 in GC cells were detected by real-time reverse transcription-polymerase chain reaction or enzyme-linked immunosorbent assay (ELISA).

RESULTS: The overexpression of IL-8 resulted in an increased cell adhesion, migration and invasion, and a significant resistance to oxaliplatin in MKN-45 cells. Inhibition of IL-8 expression with small interfering RNA decreased the adhesion, migration and invasion functions and oxaliplatin resistance in KATO-III cells. IL-8 increased NF-κB and Akt activities and adhesion molecules ICAM-1, VCAM-1, and CD44 expression in GC cells.

CONCLUSION: Overexpression of IL-8 promotes the adhesion, migration, invasion, and chemoresistance of GC cells, indicating that IL-8 is an important therapeutic target in GC.

Glucose metabolism gene variants modulate the risk of pancreatic cancer

Long-term type 2 diabetes is a known risk factor for pancreatic cancer (PC). We hypothesized that genetic variants in glucose metabolism modify individual susceptibility to PC, especially those associated with diabetes. We retrospectively genotyped 26 single-nucleotide polymorphisms of 5 glucose metabolism genes: glucokinase (GCK), glutamine-fructose-6-phosphate transaminase 1 (GFPT1), glucose phosphate isomerase (GPI), hexokinase 2 (HK2), and O-linked N-acetylglucosamine transferase (OGT) in a case-control study of PC conducted at MD Anderson during 2004 to 2010. Initial genotyping was conducted in 706 patients with PC and 706 cancer-free controls by using the Sequenom method. A HK2 genotype (R844K) with low frequency of homozygous variant was further examined in additional 948 patients and 476 controls. In the combined set of 1,654 cases and 1,182 controls, we showed a significant association of the HK2 R844K GA/AA genotype with reduced PC risk (OR = 0.78; 95% CI, 0.64-0.94; P = 0.009) and a significant interaction with diabetes (P(interaction) < 0.001). The HK2 R844K GA/AA genotype was associated with a reduced risk of PC among nondiabetic individuals (OR = 0.68; 95% CI, 0.56-0.83) but with increased risk among diabetic patients (OR = 3.69; 95% CI, 2.34-5.82). These risk associations remained statistically significant when the analysis was restricted to whites or after exclusion of recent onset diabetes. No significant main effect of other genes or significant interaction of genotype with other risk factors was observed. The findings show a potential role of HK2 gene, alone or in interaction with diabetes, in modifying the risk of PC.