Cancer cell heterogeneity (CCH) is a key element in understanding cancer progression and metastasis. CCH is one of the challenges in therapeutics and diagnostics stumbling block in modern medicine. An in-vitro model of co-culture systems of MCF-7, HeLa, HEK-293, with THP-1 cells showed the occurrence of CTCs like cells with EpCAM+ and other cancer cell heterogenetic types with the Quantum Dot antibody conjugates (QDAb). This in-vitro model study could provide insights into the role of rare cancer cells and heterogeneity in metastasis, as well as the severity of infections in these patients. We successfully reported the presence of CCH based on the fluorescence ratios of the co-culture cancer cells. These short-term mimic co-cultures give a compelling and quite associated model for estimating early treatment responses in various types of cancers.