Inositol hexaphosphate inhibits growth and induces G1 arrest and apoptotic death of androgen-dependent human prostate carcinoma LNCaP cells.
Prostate cancer (PCA) is the most common invasive malignancy and the second leading cause of cancer-related deaths in the US male population. One approach to control this malignancy is its preventive intervention by dietary agents. Inositol hexaphosphate (IP6), a dietary constituent, has shown promising efficacy against various cancers; however, limited studies have been performed with IP6 against PCA. Here, we investigated the growth-inhibitory effect and associated mechanisms of IP6 in androgen-dependent human prostate carcinoma LNCaP cells. IP6 treatment of cells resulted in a strong growth inhibition and an increase in G1 cell population. In mechanistic studies, IP6 resulted in an increase in cyclin-dependent kinase inhibitors (CDKIs) Cip1/p21 and Kip1/p27 levels, together with a decrease in cyclin-dependent kinase (CDK) 4 and cyclin D1 protein levels. An increase in CDKI levels by IP6 also led to a concomitant increase in their interactions with CDK2 and CDK4, together with a strong decrease in the kinase activity of both CDKs. Downstream in CDKI-CDK-cyclin cascade, consistent with its inhibitory effect on CDK kinase activity, IP6 treatment of cells increased hypophosphorylated levels of retinoblastoma (Rb) with a decrease in Rb phosphorylation at serine 780, 807, and 811 sites, and caused a moderate to strong decrease in the levels of transcription factors E2F1, E2F4, and E2F5. In other studies, IP6 caused a dose- and a time-dependent apoptotic death of LNCaP cells, and a decrease in Bcl2 levels, causing a strong increase in Bax versus Bcl2 ratio, as well as an inhibition of constitutively active AKT phosphorylation. Taken together, these molecular alterations provide an insight into IP6-caused growth inhibition, G1 arrest, and apoptotic death of human prostate carcinoma LNCaP cells. Because early clinical PCA growth is an androgen-dependent response, the results of the present study employing androgen-dependent LNCaP cells suggest that IP6 has promise and potential to be effective against PCA.
Agarwal
Chapla
C
Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Cancer Center, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Dhanalakshmi
Sivanandhan
S
Singh
Rana P
RP
Agarwal
Rajesh
R
D000728:Androgens / Q000502:physiology*; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis; D016203:CDC2 Protein Kinase / Q000378:metabolism; D042846:CDC2-CDC28 Kinases / Q000378:metabolism; D002277:Carcinoma / Q000188:drug therapy* / Q000378:metabolism; D045744:Cell Line, Tumor; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects; D006801:Humans; D008297:Male; D009376:Neoplasms, Hormone-Dependent / Q000188:drug therapy* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010833:Phytic Acid / Q000494:pharmacology* / Q000627:therapeutic use; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D016160:Retinoblastoma Protein / Q000378:metabolism
D000728:Androgens; D000970:Antineoplastic Agents; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D010833:Phytic Acid; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495900:CDK4 protein, human; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases