Isoenzyme pattern and subcellular localization of hexokinases in human breast cancer and nonpathological breast tissue

Abstract

Subcellular distribution of hexokinase (HK) isoenzymes in 22 human breast cancers (21 primary cancers and 1 axillary metastatic growth) and 7 non-pathological human mammary gland tissue samples was studied with starch gel electrophoresis on isolated cell fractions obtained by differential centrifugation. Fractions used were cytosol, mitochondria and microsomes. A comparison of two methods for detecting HK activity was made, yielding different results regarding HK II and HK III. A method based on the ability of NADPH to fluoresce in UV gave a constant pattern of HK isoenzymes. In non-pathological breast tissue, only HK I was seen, i.e. in the cytosol and the microsomal fractions. HK I was also seen in all fractions of the cancers, but another more anodal band of HK I, as well as HK II and HK III, consistently appeared in the cytosol fractions. The more commonly used staining technique with tetrazolium dye revealed HK II in 45% and HK III in 50% of the samples. The pattern of HK isoenzymes in the cancers was the same irrespective of estrogen and progesterone cytosolic receptor contents and the histology of the tumors. The fluorescence method is, therefore, much more sensitive than the tetrazolium technique for detecting HK activity after electrophoresis and could explain difference in results obtained by various laboratories.

The permeability transition pore complex in cancer cell death

“…In keeping with its activity to inhibit the PTP by protein-protein interactions, HKII is found upregulated in tumors (Shinohara et al, 1991;Rempel et al, 1996;AzoulayZohar et al, 2004). One study detected this enzyme in 45% of all breast tumor samples investigated (Gudnason et al, 1984). Besides the activation of the promotor of the HKII gene, an amplification of the gene has also been observed (Rempel et al, 1996).…”

Specific polypeptide differences in normal versus malignant human breast tissues by two-dimensional electrophoresis

“…Non-pathological samples were treated in the same way as tumor samples. No differences in the hexokinase isoenzyme patterns were observed between freshly prepared samples and previously frozen ones [11].…”

“…Postmitochondrial and cytosolic fractions (5-10 mg/ml) were lyophilized to dryness for concentration and stored desiccated at -70 ° C prior to electrophoresis. No difference in hexokinase isozyme patterns was detected before and after lyophilization [11].…”

“…Although these receptor assays are extremely useful diagnostically, numerous inherent problems associated with steroid-receptor binding studies in general have limited their usefulness, and have prompted searches for additional biochemical markers of transformation-associated changes in human breast tumors in order to detect, diagnose, and treat this form of cancer as early as possible [5][6][7][8][9][10][11]. In the present study we have used the high resolving power of 2D-PAGE, in combination with computer assisted qualitative and quantitative analysis of between 600-800 polypeptides from cellular homogenates and cytosolic preparations from human breast tumors and from non-malignant breast tissue samples, in an attempt to define sets of cellular polypeptides which may be involved in (or associated with) the malignant transformation of human breast tissue.…”

La conexina 43 como modulador de la captación de glucosa en astrocitos

“…De hecho, la Hx-2, se expresa en niveles significativamente altos en los gliomas (Muzi et al, 2001). Este mismo patrón de comportamiento se observa en otras células tumorales, donde el 45% de todas las muestras examinadas presentaron altos niveles de esta isoforma (Gudnason et al, 1984). En este sentido, aunque la Hx-1 es la isoforma predominante en la retina, los retinoblastomas expresan cantidades considerables de la Hx-1 (Beemer et al, 1982).…”