Effect of Cyclodextrin Charge on Complexation of Neutral and Charged Substrates: Comparison of (SBE)7M-β-CD to HP-β-CD

Purpose. To understand the role of charge in substrate/cyclodextrin complexation by comparing the binding of neutral and charged substrates to a neutral cyclodextrin, such as hydroxypropyl –CD (HP––CD) with 3.5 degrees of substitution, and an anionically charged cyclodextrin, such as sulfobutyl ether –CD ((SBE)_7M––CD) with 6.8 degrees of substitution. Method. HP––CD and (SBE)_7M––CD were evaluated in their ability to form inclusion complexes with neutral compounds, as well as to cationic and anionic substrates in their charged and uncharged forms. The complexation constants (K_c) were determined via a UV spectrophotometric technique, by monitoring the change in substrate absorbance upon incremental addition of a concentrated cyclodextrin solution. The role of electrostatic interaction was probed by observing K_c as a function of solution ionic strength. Results. Neutral molecules displayed a stronger interaction with (SBE)_7M––CD compared to HP––CD. In those cases where the guest possessed a charge (positive or negative), HP––CD/substrate complexes exhibited a decrease in complexation strength (2 to 31 times lower) compared to the neutral forms of the same substrate. The same was true (but to a larger extent, 41 times lower) for negatively charged molecules binding to (SBE)_7M––CD due to charge–charge repulsion. However, positively charged molecules interacting with the negatively charged (SBE)_7M––CD displayed a similar binding capability as their neutral counterpart, due to charge–charge attraction. Further evaluation through manipulation of solution ionic strength revealed strong electrostatic interactions between substrate and cyclodextrin charges. In addition, the studies suggested that on average two sulfonates out of seven may be involved in forming ionic attraction or repulsion effects with the positive charges on prazosin and papaverine, or negative charges of ionized naproxen and warfarin. Conclusions. Presence of charge on the cyclodextrin structure provides an additional site of interaction compared to neutral cyclodextrins, which may be modified using solution ionic strength.     

MHC class I negative phenotype of disseminated tumor cells in bone marrow is associated with poor survival in R0M0 breast cancer patients

Changing the major histocompatibility complex (MHC) class I phenotype is a pivotal strategy of tumor cells to circumvent an effective immune response and is associated with tumor progression in cancer patients. Epithelial cells in bone marrow have been detected in various tumor types, but the clinical observation that only a portion of the patients with a positive bone marrow status develops solid bone metastasis suggests a certain molecular equipment of the isolated tumor cells as a prerequisite for metastatic formation. In the present study the prognostic impact of the MHC class I phenotype of disseminated epithelial cells in bone marrow was evaluated in a cohort of 30 curatively resected (R0) patients without distant metastases (M0) (designated R0M0) who had minimal residual disease. Immunocytochemical analysis using the alkaline/anti-alkaline immunogold double staining procedure revealed a heterogeneous MHC class I expression profile [monoclonal antibody (mAb) W6/32] of the epithelial cells (mAb CK2). In 16 patients (53.3%) all epithelial cells were human leukocyte antigen (HLA) class I-positive (CK2+//W6/32+ phenotype). Eight patients (26.7%) showed complete loss of the HLA class I molecules (CK2+//W6/32- phenotype) and in 6 patients (20%) partial loss of HLA class I expression was found (CK2+//W6/32+ and - phenotype). CK2+ cells with the HLA class I negative phenotype (CK2+//W6/32- phenotype and CK2+//W6/32+ and - phenotype) were often derived from poorly differentiated (G3) primary breast carcinomas (p = 0.036) and were associated with short survival of the R0M0 patients (follow-up 15-98 months, log rank p = 0.072). These findings support the necessity to develop immmunotherapeutic strategies leading to the restoration of MHC class I positive phenotype.     

Selective labelling of bradykinin receptor subtypes in WI38 human lung fibroblasts.

1. Binding of the B1 bradykinin receptor radioligand, [3H]-des-Arg10-kallidin (-KD) and the B2 receptor radioligand [3H]-bradykinin (-BK) was investigated in membranes prepared from WI38 human foetal lung fibroblasts. 2. One-site analysis of the saturation data for [3H]-des-Arg10-KD gave an equilibrium dissociation constant (KD) value of 0.51 +/- 0.12 nM and a maximum receptor density (Bmax) of 260 +/- 49 fmol mg-1 of protein. [3H]-des-Arg10-KD binding was displaced by ligands in the order: des-Arg10-KD > KD > > des-Arg9[Leu8]-BK > des-Arg9-BK > Hoe 140 > > BK, implying that it was binding selectively to B1 receptors. 3. One-site analysis of the binding of [3H]-BK to W138 membranes indicated that it had a KD value of 0.25 +/- 0.06 nM and a Bmax of 753 +/- 98 fmol mg-1 of protein. The potencies for displacement of [3H]-BK binding were: Hoe 140 > > BK = KD > > > des-Arg10-KD = des-Arg9[Leu8]-BK = des-Arg9-BK, which was consistent with binding to B2 receptors. 4. This is the first characterization of [3H]-des-Arg10-KD binding to include both kinetic and equilibrium data, and demonstrates that [3H]-des-Arg10-KD has a high affinity for human B1 bradykinin receptors and is sufficiently selective to be used as a radioligand for B1 receptors in human cells or tissues expressing an excess of B2 BK receptors.